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Superconducting circuits are well established tools for quantum sensing anda promising new platform for quantum computing. Typically these quantumcircuits operate at microwave frequencies where the thermal noise at 10mK in a dilution refrigerator is small compared to the ground-state energy.Controlling the quantum state of these circuits requires well-timed, phase-coherent microwave pulses. This thesis describes an instrument based onsynchronous direct digital synthesis and sampling at microwave frequenciesto control and measure the response of superconducting quantum circuits.This all-digital approach allows for up and down conversion to microwavebands without analog IQ mixers, reducing the complexity of the controlsystem and enabling advanced signal processing via software. The thesisalso describes how the instrument is used to explore the quantum propertiesof a variety of different superconducting circuits.We characterise and benchmark a sample containing two transmon qubitsconnected by a parametric coupler. Randomized benchmarking showscoherence-limited fidelity of single-qubit gates. We successfully operate atwo-qubit iSWAP gate where controlling the relative phase of microwavepulses is necessary. Using a 3D cavity coupled to a transmon qubit we createarbitrary bosonic states using interleaved sequences of pulses which displacethe cavity oscillation and perform selective number-dependent arbitrary-phase (SNAP) gates. In the area of measurement-based quantum computingwe explore the generation of entangled states of travelling waves generatedby scattering vacuum noise off a Josephson parametric amplifier. The en-tanglement is generated and detected using a phase-coherent pumping anddetection scheme at multiple frequencies. We apply this same scheme to alsostudy frequency-domain entanglement between multiple standing waves ofa nonlinear surface-acoustic-wave resonator. The multifrequency capabili-ties of the instrument are also used to study single-photon detectio, Supraledande kretsar är väletablerade för kvantsensorer och en lovande nyplattform för kvantdatorer. Kretsarna är normalt designade för att använ-das vid mikrovågsfrekvenser där det termiska bruset vid 10 mK i en kryostatär litet jämfört med grundtillståndens energi. Att kontrollera kvanttillståndi sådana kretsar kräver vältajmade, faskoherenta mikrovågspulser. Dennaavhandling beskriver ett instrument baserat på synkroniserad direkt digi-tal syntes och sampling vid mikrovågsfrekvenser avsett att kontrollera ochmäta svar från supraledande kvantkretsar. Detta helt digitala tillvägagångs-sätt tillåter upp- och nedkonvertering till mikrovågsfrekvenser utan analogaIQ-mixers vilket minskar instrumentets komplexitet och möjliggör avance-rad signalbehandling i mjukvara. Avhandlingen beskriver också hur instru-mentet används till att utforska kvantegenskaperna hos olika supraledandekretsar.Vi karakteriserar och utvärderar prestanda på ett prov innehållande tvåkvantbitar av typen ’transmon’ sammankopplade med en parametrisk kopp-lare. ’Randomized benchmarking’ visar att noggrannheten på en-kvantbitgrindar är begränsade av kvantbitens koherenstid. Vi lyckas framgångsriktgenomföra en iSWAP-grind där styrning av den relativa fasen på mikrovågs-pulser är nödvändig. Med hjälp av en 3D-kavitet kopplad till en ’transmon’kvantbit skapar vi godtyckliga bosoniska tillstånd via sammanflätade se-kvenser av pulser som förskjuter kavitetsoscillationen och selective number-dependent arbitrary phase (SNAP) grindar. I kategorin mätningabasera-de kvantberäkningar utforskar vi generering av sammanflätade tillstånd iform av vågor som skapas genom att låta vakuumbrus reflekteras på enJosephson-parametrisk förstärkare. Sammanflätningen genereras och detek-teras via faskoherent pump- och detektion på flera frekvenser. Vi tillämparsamma metod för att studera sammanflätning mellan stående vågor i en icke-linjär akustisk ytvågresonator. Instrumentets multifrekvensfunktioner an-vänds också till att stu, QC 2023-12-22

Superconducting circuits are well established tools for quantum sensing anda promising new platform for quantum computing. Typically these quantumcircuits operate at microwave frequencies where the thermal noise at 10mK in a dilution refrigerator is small compared to the ground-state energy.Controlling the quantum state of these circuits requires well-timed, phase-coherent microwave pulses. This thesis describes an instrument based onsynchronous direct digital synthesis and sampling at microwave frequenciesto control and measure the response of superconducting quantum circuits.This all-digital approach allows for up and down conversion to microwavebands without analog IQ mixers, reducing the complexity of the controlsystem and enabling advanced signal processing via software. The thesisalso describes how the instrument is used to explore the quantum propertiesof a variety of different superconducting circuits.We characterise and benchmark a sample containing two transmon qubitsconnected by a parametric coupler. Randomized benchmarking showscoherence-limited fidelity of single-qubit gates. We successfully operate atwo-qubit iSWAP gate where controlling the relative phase of microwavepulses is necessary. Using a 3D cavity coupled to a transmon qubit we createarbitrary bosonic states using interleaved sequences of pulses which displacethe cavity oscillation and perform selective number-dependent arbitrary-phase (SNAP) gates. In the area of measurement-based quantum computingwe explore the generation of entangled states of travelling waves generatedby scattering vacuum noise off a Josephson parametric amplifier. The en-tanglement is generated and detected using a phase-coherent pumping anddetection scheme at multiple frequencies. We apply this same scheme to alsostudy frequency-domain entanglement between multiple standing waves ofa nonlinear surface-acoustic-wave resonator. The multifrequency capabili-ties of the instrument are also used to study single-photon detectio, Supraledande kretsar är väletablerade för kvantsensorer och en lovande nyplattform för kvantdatorer. Kretsarna är normalt designade för att använ-das vid mikrovågsfrekvenser där det termiska bruset vid 10 mK i en kryostatär litet jämfört med grundtillståndens energi. Att kontrollera kvanttillståndi sådana kretsar kräver vältajmade, faskoherenta mikrovågspulser. Dennaavhandling beskriver ett instrument baserat på synkroniserad direkt digi-tal syntes och sampling vid mikrovågsfrekvenser avsett att kontrollera ochmäta svar från supraledande kvantkretsar. Detta helt digitala tillvägagångs-sätt tillåter upp- och nedkonvertering till mikrovågsfrekvenser utan analogaIQ-mixers vilket minskar instrumentets komplexitet och möjliggör avance-rad signalbehandling i mjukvara. Avhandlingen beskriver också hur instru-mentet används till att utforska kvantegenskaperna hos olika supraledandekretsar.Vi karakteriserar och utvärderar prestanda på ett prov innehållande tvåkvantbitar av typen ’transmon’ sammankopplade med en parametrisk kopp-lare. ’Randomized benchmarking’ visar att noggrannheten på en-kvantbitgrindar är begränsade av kvantbitens koherenstid. Vi lyckas framgångsriktgenomföra en iSWAP-grind där styrning av den relativa fasen på mikrovågs-pulser är nödvändig. Med hjälp av en 3D-kavitet kopplad till en ’transmon’kvantbit skapar vi godtyckliga bosoniska tillstånd via sammanflätade se-kvenser av pulser som förskjuter kavitetsoscillationen och selective number-dependent arbitrary phase (SNAP) grindar. I kategorin mätningabasera-de kvantberäkningar utforskar vi generering av sammanflätade tillstånd iform av vågor som skapas genom att låta vakuumbrus reflekteras på enJosephson-parametrisk förstärkare. Sammanflätningen genereras och detek-teras via faskoherent pump- och detektion på flera frekvenser. Vi tillämparsamma metod för att studera sammanflätning mellan stående vågor i en icke-linjär akustisk ytvågresonator. Instrumentets multifrekvensfunktioner an-vänds också till att stu, QC 2023-12-22

The Gaussian phase-space representation can be used to implement quantum dynamics for fermionic particles numerically. To improve numerical results, we explore the use of dynamical diffusion gauges in such implementations. This is achieved by benchmarking quantum dynamics of few-body systems against independent exact solutions. A diffusion gauge is implemented here as a so-called noise-matrix, which satisfies a matrix equation defined by the corresponding Fokker-Planck equation of the phase-space representation. For the physical systems with fermionic particles considered here, the numerical evaluation of the new diffusion gauges allows us to double the practical simulation time, compared with hitherto known analytic noise-matrices. This development may have far reaching consequences for future quantum dynamical simulations of many-body systems.

Interfacing graphene with other low-dimensional material has gained attentions recently due to its potential to stimulate new physics and device innovations for optoelectronic and electronic applications. Here, we exploit a solution-processed approach to introduce colloidal quantum dot (CQD) to the bilayer graphene device. The magnetotransport properties of the graphene device is drastically altered due to the presence of the CQD potential, leading to the observation of AB-like oscillation in the quantum Hall regime and screening of the intervalley scattering. The anomalous magnetotransport behavior is attributed to the coulombic scattering introduced by the CQDs and is shown to be highly asymmetric depending on the polarity of the transport carriers. These results prove the potential of such flexible method for engineering microscopic scattering process and performance of the graphene device that may lead to intriguing device application in such hybrid system., Funding Agencies|National Natural Science Foundation of China [12374035, 11974026]; National Key Research and Devel- opment Program of China [2017YFA0303304]; Science Foundation of Jihua Laboratory [2021B0301030003-03]; Knut and Alice Wallenberg Foundation [KAW 2020.0029]

Hydrogen as an interstitial solute at grain boundaries (GBs) can have a catastrophic impact on the mechanical properties of many metals. Despite the global research effort, the underlying hydrogen-GB interactions in polycrystals remain inadequately understood. In this study, using Voronoi tessellations and atomistic simulations, we elucidate the hydrogen segregation energy spectrum at the GBs of polycrystalline nickel by exploring all the topologically favorable segregation sites. Three distinct peaks in the energy spectrum are identified, corresponding to different structural fingerprints. The first peak ( -0.205 eV) represents the most favorable segregation sites at GB core, while the second and third peaks account for the sites at GB surface. By incorporating a thermodynamic model, the spectrum enables the determination of the equilibrium hydrogen concentrations at GBs, unveiling a remarkable two to three orders of magnitude increase compared to the bulk hydrogen concentration reported in experimental studies. The identified structures from the GB spectrum exhibit vastly different behaviors in hydrogen segregation and diffusion, with the low-barrier channels inside GB core contributing to short-circuit diffusion, while the high energy gaps between GB and neighboring lattice serving as on-plane diffusion barriers. Mean square displacement analysis further confirms the findings, and shows that the calculated GB diffusion coefficient is three orders of magnitude greater than that of lattice. The present study has a significant implication for practical applications since it offers a tool to bridge the gap between atomic-scale interactions and macroscopic behaviors in engineering materials.& COPY; 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

Hydrogen as an interstitial solute at grain boundaries (GBs) can have a catastrophic impact on the mechanical properties of many metals. Despite the global research effort, the underlying hydrogen-GB interactions in polycrystals remain inadequately understood. In this study, using Voronoi tessellations and atomistic simulations, we elucidate the hydrogen segregation energy spectrum at the GBs of polycrystalline nickel by exploring all the topologically favorable segregation sites. Three distinct peaks in the energy spectrum are identified, corresponding to different structural fingerprints. The first peak ( -0.205 eV) represents the most favorable segregation sites at GB core, while the second and third peaks account for the sites at GB surface. By incorporating a thermodynamic model, the spectrum enables the determination of the equilibrium hydrogen concentrations at GBs, unveiling a remarkable two to three orders of magnitude increase compared to the bulk hydrogen concentration reported in experimental studies. The identified structures from the GB spectrum exhibit vastly different behaviors in hydrogen segregation and diffusion, with the low-barrier channels inside GB core contributing to short-circuit diffusion, while the high energy gaps between GB and neighboring lattice serving as on-plane diffusion barriers. Mean square displacement analysis further confirms the findings, and shows that the calculated GB diffusion coefficient is three orders of magnitude greater than that of lattice. The present study has a significant implication for practical applications since it offers a tool to bridge the gap between atomic-scale interactions and macroscopic behaviors in engineering materials.& COPY; 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

Organic semiconductors that emit by the process of multi-resonance thermally activated delayed fluorescence (MR-TADF) can deliver narrowband and efficient electroluminescence while being processable from solvents and metal-free. This renders them attractive for use as the emitter in sustainable light-emitting electrochemical cells (LECs), but so far reports of narrowband and efficient MR-TADF emission from LEC devices are absent. Here, this issue is addressed through careful and systematic material selection and device development. Specifically, the authors show that the detrimental aggregation tendency of an archetypal rigid and planar carbazole-based MR-TADF emitter can be inhibited by its dispersion into a compatible carbazole-based blend host and an ionic-liquid electrolyte, and it is further demonstrated that the tuning of this active material results in a desired balanced p- and n-type electrochemical doping, a high solid-state photoluminescence quantum yield of 91%, and singlet and triplet trapping on the MR-TADF guest emitter. The introduction of this designed metal-free active MR-TADF material into a LEC, employing air-stabile electrodes, results in bright blue electroluminescence of 500 cd m−2, which is delivered at a high external quantum efficiency of 3.8% and shows a narrow emission profile with a full-width-at-half-maximum of 31 nm.

Graphite oxide (GO) is a hydrophilic, layered material prepared by oxidation of graphite. In the first part of this thesis, we studied materials produced from GO by intercalation and functionalization. The second part of the thesis was focused on supercapacitor applications of high surface area carbons prepared from GO using chemical activation. A detailed study of acetylated GO (AcGO) was performed to verify structure and properties of this material. Reports from 1960’s suggested that AcGO has “pillared” structure. Our analysis showed that the AcGO demonstrates expanded structure due to acetylation but exhibits negligible specific surface area and should not be considered as a pillared material. Pillared reduced GO (prGO) was prepared by applying mild annealing to GO material pillared with tetrapod-shaped amine molecules. PrGO showed relatively high surface area due to remaining pillaring molecules in the structure. The prGO is hydrophobic and exhibits 100x improved conductivity compared to precursor. PrGO is one of few true pillared structures reported in literature so far, and the first ever prepared starting from pillared GO. We also investigated the sorption of common dyes, methylene blue (MB), rose bengal (RB) and crystal violet (CV), by multilayered graphene oxide materials. We found that MB dissolved in ethanol intercalates the GO structure, as evidenced by significant expansion of inter-layer distance, and increase in weight due to sorption. In contrast to MB, GO is not easily intercalated by CV and RB dyes. We believe that the flat MB molecule shape allows easier insertion between GO layers compared to twisted and non-flat CV and RB molecules. Our results suggest that penetration into GO inter-layers depends not only on the size of molecules, but also on the shape. Temperature dependent study of structures formed by Brodie GO (BGO) in liquid alkyl alcohols was performed for a set starting from undecyl alcohol (no. of C=11) and up to behenyl alcohol (no.

Non-fullerene electron acceptors have emerged as promising alternatives to traditional electron-acceptors in the active layers of organic photovoltaics. This is due to their tunable energy levels, optical response in the visible light spectrum, high electron mobility, and photochemical stability. In this study, the electronic properties of two representative non-fullerene acceptors, ITIC and Y5, have been calculated within the framework of density functional theory using a range of hybrid and non-hybrid density functionals. Screened range-separated hybrid (SRSH) approaches were also tested. The results are analyzed in light of the previously reported experimental outcomes. Specifically, we have calculated the oxidation and reduction potentials, fundamental and optical gaps, the highest occupied molecular orbital and lowest unoccupied molecular orbital energies, and exciton binding energies. Additionally, we have investigated the effects of the medium dielectric constant on these properties employing a universal implicit solvent model. It was found that hybrid functionals generally perform poorly in predicting oxidation potentials, while non-hybrid functionals tend to overestimate reduction potentials. The inclusion of a large Hartree-Fock contribution to the global or long range was identified as the source of inaccuracy for many hybrid functionals in predicting both redox potentials and the fundamental and optical gaps. Corroborating with the available literature, ∼50% of all tested functionals predicted very small exciton binding energies, within the range of ±0.1 eV, that become even smaller by increasing the dielectric constant of the material. Finally, the OHSE2PBE and tHCTHhyb functionals and the optimal tuning SRSH approach emerged as the best-performing methods, with good accuracy in the description of the electronic properties of interest.

The idea of strain based manipulation of spins in magnetic two-dimensional (2D) van der Waal (vdW) materials leads to the development of new generation spintronic devices. Magneto-strain arises in these materials due to the thermal fluctuations and magnetic interactions which influences both the lattice dynamics and the electronic bands. Here, we report the mechanism of magneto-strain effects in a vdW material CrGeTe3 across the ferromagnetic (FM) transition. We find an isostructural transition in CrGeTe3 across the FM ordering with first order type lattice modulation. Larger in-plane lattice contraction than out-of-plane give rise to magnetocrystalline anisotropy. The signature of magneto-strain effects in the electronic structure are shift of the bands away from the Fermi level, band broadening and the twinned bands in the FM phase. We find that the in-plane lattice contraction increases the on-site Coulomb correlation (U-eff) between Cr atoms resulting in the band shift. Out-of plane lattice contraction enhances the d - p hybridization between Cr-Ge and Cr-Te atoms which lead to band broadening and strong spin-orbit coupling (SOC) in FM phase. The interplay between U(eff )and SOC out-of-plane gives rise to the twinned bands associated with the interlayer interactions while the in-plane interactions gives rise to the 2D spin polarized states in the FM phase.

Very fast interface traps have recently been suggested to be the main cause behind the rather poor inversion channel mobility in nitrided SiC metal-oxide-semiconductor-field-effect-transistors (MOSFETs). Using capacitance voltage analysis and conductance spectroscopy on metal oxide semiconductor capacitors, at cryogenic temperatures, we find that these fast traps are absent in oxides made by sodium enhanced oxidation, and high inversion channel-carrier mobility in MOSFETs made by sodium enhanced oxidation is observed., Funding Agencies|Icelandic Center for Research (Rannis) [185412-052]; University of Iceland Research Fund

We experimentally investigated the detection performance of highly disordered NbxTi1-xN based superconducting nanowire single photon detectors (SNSPDs). The dependence on the composition of the transition temperature T-c for NbxTi1-xN films show a dome-like behavior on the Nb content, with a maximal T-c at x(Nb) similar to 0.65, and the Nb0.65Ti0.35N films also combine relatively large sheet resistance and intermediate residual resistivity ratio. Moreover, 60-nm-wide and 7-nm-thick Nb0.65Ti0.35N nanowires show a switching current as high as 14.5 mu A, and saturated intrinsic detection efficiency with a plateau of more than 2 mu A at 2.4 K. Finally, the corresponding SNSPDs on an alternative SiO2/Ta2O5 dielectric mirror showed a system detection efficiency of approximately 92% for 1550 nm photons, and the timing jitter is around 26 ps. Our results demonstrate that the highly disordered NbxTi1-xN films are promising for fabricating SNSPDs for near-and middle-infrared single photons with high detection efficiency and low timing jitter., Funding Agencies|National Natural Foundation of China [61971408, 61827823]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Knut and Alice Wallenberg foundation through the Wallenberg Academy Fellows program [KAW-2020.0196]; Swedish Foundation for Strategic Research (SSF) [RIF 14-0074]; Swedish Research Council VR-RFI [201900191]; Swedish Foundation for Strategic Research [RIF14-0053]; Linkoeping Electron Microscopy Laboratory

Chromium-based nitrides are used in hard, resilient coatings and show promise for thermoelectric applications due to their combination of structural, thermal, and electronic properties. Here, we investigate the electronic structures and chemical bonding correlated to the thermoelectric properties of epitaxially grown chromium-based multicomponent nitride Cr(Mo,V)Nx thin films. The small amount of N vacancies causes Cr 3d and N 2p states to appear at the Fermi level and reduces the band gap in Cr0.51N0.49. Incorporating holes by alloying of V in N-deficient CrN results in an enhanced thermoelectric power factor with marginal change in the charge transfer of Cr to N compared with Cr0.51N0.49. Further alloying of Mo, isoelectronic to Cr, increases the density of states at the Fermi level due to hybridization of the (Cr, V) 3d and Mo 4d-N 2p states in Cr(Mo,V)Nx. This hybridization and N off-stoichiometry result in more metal-like electrical resistivity and reduction in Seebeck coefficient. The N deficiency in Cr(Mo,V)Nx also depicts a critical role in reduction of the charge transfer from metal to N site compared with Cr0.51N0.49 and Cr0.50V0.03N0.47. In this paper, we envisage ways for enhancing thermoelectric properties through electronic band engineering by alloying and competing effects of N vacancies.

Charge-transport layers are essential for achieving electrically pumped perovskite lasers. However, their role in perovskite lasing is not fully understood. Here, the role of charge-transport layers on the lasing actions of perovskite films is explored by investigating the amplified spontaneous emission (ASE) thresholds. A largely reduced ASE threshold and enhanced ASE intensity is demonstrated by introducing an additional hole transport layer poly(triaryl amine) (PTAA). It is shown that the key role of the PTAA layer is to accelerate the hot-carrier cooling process by extracting holes in perovskites. With reduced hot holes, the Auger recombination loss is largely suppressed, resulting in decreased ASE threshold. This argument is further supported by the fact that the ASE threshold can be further reduced from 25.7 to 7.2 mu J cm(-2) upon switching the pumping wavelength from 400 to 500 nm to directly avoid excess hot-hole generation. This work exemplifies how to further reduce the ASE threshold with transport layer engineering through hot-hole manipulation. This is critical to maintaining the excellent gain properties of perovskites when integrating them into electrical devices, paving the way for electrically pumped perovskite lasers., Funding Agencies|European Research Council Consolidator Grant (LEAP) [101045098]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Marie Curie Fellowship [Horizon-MSCA-2021-PF, 101066960]; Horizon Europe; AFOSR [FA 9550-18-1-0472]; AFOSR

Compositionally graded channel AlGaN/GaN high electron mobility transistors (HEMTs) offer a promising route to improve device linearity, which is necessary for low-noise radio-frequency amplifiers. In this work, we demonstrate different grading profiles of a 10-nm-thick AlxGa1-xN channel from x = 0 to x = 0.1 using hot-wall metal-organic chemical vapor deposition (MOCVD). The growth process is developed by optimizing the channel grading and the channel-to-barrier transition. For this purpose, the Al-profiles and the interface sharpness, as determined from scanning transmission electron microscopy combined with energy-dispersive x-ray spectroscopy, are correlated with specific MOCVD process parameters. The results are linked to the channel properties (electron density, electron mobility, and sheet resistance) obtained by contactless Hall and terahertz optical Hall effect measurements coupled with simulations from solving self-consistently Poisson and Schrodinger equations. The impact of incorporating a thin AlN interlayer between the graded channel and the barrier layer on the HEMT properties is investigated and discussed. The optimized graded channel HEMT structure is found to have similarly high electron density (similar to 9 x 10(12) cm(-2)) as the non-graded conventional structure, though the mobility drops from similar to 2360 cm(2)/V s in the conventional to similar to 960 cm(2)/V s in the graded structure. The transconductance g(m) of the linearly graded channel HEMTs is shown to be flatter with smaller g(m) and g(m) as compared to the conventional non-graded channel HEMT implying improved device linearity. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)., Funding Agencies|Swedish Governmental Agency for Innovation Systems (VINNOVA); Lund University; Linkoeping University; Chalmers University of Technology [2022-03139]; Ericsson; Epiluvac; FMV; Gotmic; Hexagem; Hitachi Energy; On Semiconductor; Region Skane SAAB; SweGaN; Volvo Cars; UMS; Swedish Research Council VR; Swedish Foundation for Strategic Research; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University; KAW Foundation [2016-00889, 2022-04812]; Swedish Research Council and the Foundation [RIF14-055, EM16-0024, STP19-0008]; [2009-00971]; [2021-00171]; [RIF21-0026]

High-entropy materials, an exciting new class of structural materials involvingfive or more elements, are emerging as unexplored ground forsuperconductors. Here, the effects of nitrogen stoichiometry are investigatedon local chemical structure of TiZrNbTa-based thin films by variousX-ray-based techniques. Lattice distortion and short-range order of a set ofTiZrNbTaNxsamples, including bond lengths of different atomic pairs andcoordination numbers of substituting atoms are quantitatively studied. Themaximum superconducting transition temperature Tcis found at 10 K for anear-stoichiometric (TiZrNbTa)N1.08film, which is>8 K measured for ametallic TiZrNbTa film. The underlying electronic structure and chemicalbonding in these high entropy nitrides thus influence the superconductingmacroscopic properties., Funding agencies: the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No. 2009 00971), the VINNOVA Competence Centre FunMat-II (grant no. 2016–05156), the Knut and Alice Wallenberg foundation through the Wallenberg Academy Fellows program (KAW-2020.0196), and the Swedish Research Council under project number 2021–03826. Financial support for the operation of the accelerator laboratory in Uppsala by VR-RFI (Contract No. 2017-00646_9) and the Swedish Foundation for Strategic Research (SSF, Contract No. RIF14-0053), the Swedish Energy Research (Grant No.43606-1) and the CarlTryggers Foundation (CTS23:2746, CTS20:272, CTS16:303, CTS14:310).The authors acknowledge the MAX IV Laboratory for beamtime on the BALDER beamline for proposal 20200219. Research conducted at MAX IV, a Swedish national user facility, was supported by the Swedish Research council under contract 2018–07152, the Swedish Governmental Agency for Innovation Systems (VINNOVA) under contract 2018–04969, and Formas under contract 2019–02496.

Helical plants have the ability of tropisms to respond to natural stimuli, and biomimicry of such helical shapes into artificial muscles has been vastly popular. However, the shape-mimicked actuators only respond to artificially provided stimulus, they are not adaptive to variable natural conditions, thus being unsuitable for real-life applications where on-demand, autonomous operations are required. Novel artificial muscles made of hierarchically patterned helically wound yarns that are self-adaptive to environmental humidity and temperature changes are demonstrated here. Unlike shape-mimicked artificial muscles, a unique microstructural biomimicking approach is adopted, where the muscle yarns can effectively replicate the hydrotropism and thermotropism of helical plants to their microfibril level using plant-like microstructural memories. Large strokes, with rapid movement, are obtained when the individual microfilament of yarn is inlaid with hydrogel and further twisted into a coil-shaped hierarchical structure. The developed artificial muscle provides an average actuation speed of approximate to 5.2% s(-1) at expansion and approximate to 3.1% s(-1) at contraction cycles, being the fastest amongst previously demonstrated actuators of similar type. It is demonstrated that these muscle yarns can autonomously close a window in wet climates. The building block yarns are washable without any material degradation, making them suitable for smart, reusable textile and soft robotic devices., Funding Agencies|Australian Research Council [LP200100403, DP200101397]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009~00971]; Erling-Persson Family Foundation [2020-0054]; University of Queensland, as part of the Wiley - The University of Queensland agreement via the Council of Australian University Librarians

The angular dependence of the deposition rates due to ions and neutrals in high-power impulse magnetron sputtering (HiPIMS) discharges with a titanium target were determined experimentally using a magnetically shielded and charge-selective quartz crystal microbalance (or ionmeter). These rates have been established as a function of the argon working gas pressure, the peak discharge current density, and the pulse length. For all explored cases, the total deposition rate exhibits a heart-shaped profile and the ionized flux fraction peaks on the discharge axis normal to the cathode target surface. This heart-shaped pattern is found to be amplified at increasing current densities and reduced at increased working gas pressures. Furthermore, it is confirmed that a low working gas pressure is beneficial for achieving high deposition rates and high ionized flux fractions in HiPIMS operation., Funding Agencies|Swedish Research Council [VR 2018-04139]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University (Faculty Grant SFO-Mat-LiU ) [2009-00971]; Icelandic Research Fund [196141]; Evatec AG

Paramagnetic defects and nuclear spins are the major sources of magnetic-field-dependent spin relaxation in point-defect quantum bits. The detection of related optical signals has led to the development of advanced relaxometry applications with high spatial resolution. The nearly degenerate quartet ground state of the silicon-vacancy qubit in silicon carbide (SiC) is of special interest in this respect, as it gives rise to relaxation-rate extrema at vanishing magnetic field values and emits in the first near-infrared transmission window of biological tissues, providing an opportunity for the development of sensing applications for medicine and biology. However, the relaxation dynamics of the silicon-vacancy center in SiC have not yet been fully explored. In this paper, we present results from a comprehensive theoretical investigation of the dipolar spin relaxation of the quartet spin states in various local spin environments. We discuss the underlying physics and quantify the magnetic field and spin-bath-dependent relaxation time T1. Using these findings, we demonstrate that the silicon-vacancy qubit in SiC can implement microwave-free low-magnetic-field quantum sensors of great potential., Funding Agencies|Knut and Alice Wallenberg Foundation [KAW 2018.0071]; Swedish e -Science Research Center (SeRC); Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkping University (LiU) [2009-00971]; European Union project QuanTELCO [862721]; National Research, Development, and Innovation Office of Hungary within the Quantum Information National Laboratory of Hungary [2022-2.1.1-NL-2022- 00004, FK 145395]; Swedish National Infrastructure for Computing (SNIC) - Swedish Research Council [2018-05973]; LiU local resources at the National Supercomputer Centre (NSC) [2015-00017-60]

A family of magnetic halide double perovskites (HDPs) have recently attracted attention due to their potential to broaden application areas of halide double perovskites into, e.g., spintronics. Up to date the theoretical modeling of these systems have relied on primitive approximations to the density functional theory (DFT). In this paper, we study structural, electronic and magnetic properties of the Fe3+-containing HDPs Cs2AgFeCl6 and Cs2NaFeCl6 using a combination of more advanced DFT-based methods, including DFT + U, hybrid-DFT, and treatments of various magnetic states. We examine the effect of varying the effective Hubbard parameter, U-eff, in DFT + U and the mixing-parameter, alpha, in hybrid DFT on the electronic structure and structural properties. Our results reveal a set of localized Fe(d) states that are highly sensitive to these parameters. Cs2AgFeCl6 and Cs2NaFeCl6 are both antiferromagnets with Neel temperatures well below room temperature and are thus in their paramagnetic (PM) state at the external conditions relevant to most applications. Therefore, we have examined the effect of disordered magnetism on the electronic structure of these systems and find that while Cs2NaFeCl6 is largely unaffected, Cs2AgFeCl6 shows significant renormalization of its electronic band structure., Funding Agencies|Knut and Alice Wallenberg Foundation [KAW 2019.0082]; Wallenberg Academy Scholar [KAW-2018.0194]; Swedish Government [2009-00971]; Swedish Government Strategic Research Areas in Materials Science on Functional Materials at Linkoping University [2009-00971]; Swedish Research Council [2019-05551, 2018-05973, 854843]; ERC [2022-06725]

Non-fullerene electron acceptors have emerged as promising alternatives to traditional electron-acceptors in the active layers of organic photovoltaics. This is due to their tunable energy levels, optical response in the visible light spectrum, high electron mobility, and photochemical stability. In this study, the electronic properties of two representative non-fullerene acceptors, ITIC and Y5, have been calculated within the framework of density functional theory using a range of hybrid and non-hybrid density functionals. Screened range-separated hybrid (SRSH) approaches were also tested. The results are analyzed in light of the previously reported experimental outcomes. Specifically, we have calculated the oxidation and reduction potentials, fundamental and optical gaps, the highest occupied molecular orbital and lowest unoccupied molecular orbital energies, and exciton binding energies. Additionally, we have investigated the effects of the medium dielectric constant on these properties employing a universal implicit solvent model. It was found that hybrid functionals generally perform poorly in predicting oxidation potentials, while non-hybrid functionals tend to overestimate reduction potentials. The inclusion of a large Hartree-Fock contribution to the global or long range was identified as the source of inaccuracy for many hybrid functionals in predicting both redox potentials and the fundamental and optical gaps. Corroborating with the available literature, ∼50% of all tested functionals predicted very small exciton binding energies, within the range of ±0.1 eV, that become even smaller by increasing the dielectric constant of the material. Finally, the OHSE2PBE and tHCTHhyb functionals and the optimal tuning SRSH approach emerged as the best-performing methods, with good accuracy in the description of the electronic properties of interest.

The liquid-liquid critical point hypothesis suggests that liquid water exists in two liquid states with different local structures, so-called high- and low-density liquid (HDL, LDL). At ambient pressure water locally fluctuates between these two states, with the fluctuations becoming more pronounced as the liquid is supercooled. In this thesis, we explore the role of molecular heterogeneity in the structural dynamics of aqueous solutions, specifically investigating the interplay of different solutes in water with the hypothesized HDL-LDL fluctuations. In our experimental approach, we utilize coherent light and X-ray scattering techniques, including small- and wide-angle X-ray scattering (SAXS, WAXS), as well as correlation methods, such as dynamic light scattering (DLS) and X-ray photon correlation spectroscopy (XPCS), that enable us to probe structural dynamics at a broad range of length and time scales. Using DLS, we measure the diffusive dynamic behaviour of differently sized nanomolecular probes in supercooled water, finding that it is effectively similar and independent of probe size down to molecular scales of ≈1 nm. In contrast to single water molecules, these probes experience a similar dynamic environment, which coincides with the bulk viscosity. These results could suggest that anomalous influence from the hypothesized water fluctuations becomes apparent first on sub-nm length scales. Furthermore, we explore how the presence of small polar-organic solutes modulates the water phase diagram, utilizing glycerol-water solutions as a model system. By outrunning freezing with the rapid evaporative cooling technique, combined with ultrafast X-ray scattering at X-ray free-electron lasers (XFELs), we are able to probe the liquid structure in deeply supercooled dilute glycerol-water solutions. Our findings indicate the existence of HDL- and LDL-like fluctuations upon supercooling, with a Widom line shifted to slightly lower temperatures compared to pure water. Furt

Understanding the low-temperature properties of strongly correlated materials requires accurate measurement of the physical properties of these systems. Specific heat and nuclear spin-lattice relaxation are two such properties that allow the investigation of the electronic behavior of the system. In this thesis, nanocalorimetry is used to measure specific heat, but also as basis for new experimental approach, developed to disentangle the different contributions to specific heat at low temperatures. The technique, that we call Thermal Impedance Spectroscopy (TISP) allows independent measurement of the electronic and nuclear specific heat at low temperatures based on the frequency response of the calorimeter-sample assembly. The method also enables simultaneous measurements of the nuclear spin-lattice relaxation time (T1). The nuclear spin lattice relaxation, as 1/T1T, and electronic specific heat, as C/T, provide information about the same quantity, electronic density of states, in the system. By comparing these properties in strongly correlated systems, we can obtain insights of electronic interactions. Metallic indium is studied using thermal impedance spectroscopy from 0.3 K to 7 K at 35 T. The magnetic field dependence of nuclear spin-lattice relaxation rate is measured. Indium is a simple metallic system and the expected behavior of the nuclear spin-lattice relaxation is similar to that of the electronic specific heat. The results of the measurement are matched with the expectation from a simple metallic system and Nuclear Magnetic Resonance (NMR) measurements. This demonstrates the effectiveness of the new technique. The heavy-fermion superconductor CeCoIn5 is studied using thermal impedance spectroscopy and ac-calorimetry. This material is located near a quantum critical point (QCP) bordering antiferromagnetism, as evidenced by doping studies. The nature of its quantum criticality and unconventional superconductivity is still elusive. Contrasting specific h

Magnetic oxide nanoparticles (NPs) may interact with each-other for example via dipolar or superexchange interactions, depending whether they are in direct contact. These interparticle interactions yield both ferro- and/or antiferromagnetic coupling and modify the energy barrier of the magnetic particle, depending upon the strength of the coupling and orientation of the particles. The corresponding perturbation of the magnetic order can readily be investigated by measuring the dc-magnetization or/and the ac-susceptibility of the samples as a function of the temperature or magnetic field. Furthermore, remanence plots, First Order Reversal Curves (FORCs) analysis and magnetic relaxation measurements are ideal methods to investigate reversal mechanisms and magnetic interactions. As we show in this thesis for a set of reference nanoparticle systems comprising magnetically hard/soft ferrites, the strong interaction regime leads to interesting phenomena, including collective dynamics, exchange bias-like hysteresis loop shifts, and interface-mediated exchange-coupling of hard and soft phases. The strength of the interparticle interactions has been investigated for a set of dense assemblies of equally sized magnetically soft maghemite NPs coated with different fractions of oleic acid layer, and compared to the dilute case of silica-coated NPs. When hard exchange-biased Co-doped maghemite NPs are mixed with unbiased soft particles with equal size, we observe that dipolar interactions yield a horizontal magnetic hysteresis loop shift. We observe that the measured hysteresis bias of this system is larger than that of the exchange bias of the unmixed Co-doped particles, and assign the extra contribution to have dipolar origin ("dipolar bias"). A more complex scenario is reported for hard/soft nanostructured powder systems of Sr and Co ferrite whose morphology (epitaxial texture or lacking coherence) strongly alter the existing interparticle magnetic interactions, and in turn th

The liquid-liquid critical point hypothesis suggests that liquid water exists in two liquid states with different local structures, so-called high- and low-density liquid (HDL, LDL). At ambient pressure water locally fluctuates between these two states, with the fluctuations becoming more pronounced as the liquid is supercooled. In this thesis, we explore the role of molecular heterogeneity in the structural dynamics of aqueous solutions, specifically investigating the interplay of different solutes in water with the hypothesized HDL-LDL fluctuations. In our experimental approach, we utilize coherent light and X-ray scattering techniques, including small- and wide-angle X-ray scattering (SAXS, WAXS), as well as correlation methods, such as dynamic light scattering (DLS) and X-ray photon correlation spectroscopy (XPCS), that enable us to probe structural dynamics at a broad range of length and time scales. Using DLS, we measure the diffusive dynamic behaviour of differently sized nanomolecular probes in supercooled water, finding that it is effectively similar and independent of probe size down to molecular scales of ≈1 nm. In contrast to single water molecules, these probes experience a similar dynamic environment, which coincides with the bulk viscosity. These results could suggest that anomalous influence from the hypothesized water fluctuations becomes apparent first on sub-nm length scales. Furthermore, we explore how the presence of small polar-organic solutes modulates the water phase diagram, utilizing glycerol-water solutions as a model system. By outrunning freezing with the rapid evaporative cooling technique, combined with ultrafast X-ray scattering at X-ray free-electron lasers (XFELs), we are able to probe the liquid structure in deeply supercooled dilute glycerol-water solutions. Our findings indicate the existence of HDL- and LDL-like fluctuations upon supercooling, with a Widom line shifted to slightly lower temperatures compared to pure water. Furt

Thermally-induced transitions between bistable magnetic states of magnetic tunnel junctions (MTJ) are of interest for generating random bitstreams and for applications in stochastic computing. An applied field transverse to the easy axis of a perpendicularly magnetized MTJ (pMTJ) can lower the energy barrier (Eb) to these transitions leading to faster fluctuations. In this study, we present analytical and numerical calculations of Eb considering both coherent (macrospin) reversal and non-uniform wall-mediated magnetization reversal for a selection of nanodisk diameters and applied fields. Non-uniform reversal processes dominate for larger diameters, and our numerical calculations of Eb using the String method show that the transition state has a sigmoidal magnetization profile. The latter can be described with an analytical expression that depends on only one spatial dimension, parallel to the applied field, which is also the preferred direction of profile motion during reversal. Our results provide nanodisk energy barriers as a function of the transverse field, nanodisk diameter, and material characteristics, which are useful for designing stochastic bitstreams., Under review process in Physical Review Applied by the American Physical SocietyQC 20231102

Superconducting detectors have become essential devices for high-performance single-photon counting over a wide wavelength range with excellent time resolution. Detector fabrication typically relies on resist-based lithography processes, which can limit possibilities for device integration, e.g., on unconventional substrates. Here, we demonstrate a resist-free fabrication route for realizing superconducting nanowire single-photon detectors based on focused electron beam-induced deposition. Utilizing direct writing of a Pt-C mask, we achieved nanowire meanders with linewidths below 100 nm, operated them as superconducting devices for the detection of visible and near-infrared photons, and showed detector integration on side-polished optical fibers. Being compatible with device fabrication on curved irregular surfaces, our approach could enable superconducting detector integration in complex configurations., QC 20230515

In photovoltaics, the cover glass module has hitherto not yet been fully optimized for its purpose. Instead quite conventional architectural glass is used. In a recent review of the state-of-the-art on UV down converting dopants [1], a way forward to improve cover glasses was presented. Some of these possibilities, and others are covered in the present paper. We present possibilities to add several functionalities, instead of using dopants in the glass composition, including omnidirectional antireflection, dynamic solar control, and self-cleaning. Omni-directional anti-reflective coatings, were made by colloidal lithography templating methods on iron free glass, realizing nanopillar structures with dimensions /2 exploiting Mie scattering for wide angle light collection (Fig. 1). Yttrium oxyhydride (YHO) coatings were deposited on the nanopillar structures using magnetron sputtering methods [2]. The YHO film blocks UV light and photo-darkens upon solar light absorption and reverts to its transparent state in dark in reproducible manner [2]. In addition, the YHO film also becomes hydrophobic upon photo-darkening, acting as a self-cleaning layer. The fabricated coatings were compared with bare glass substrates. The results reveal suppressed reflectance, with acceptable anti-reflective properties up to about 50 degrees. Solar light modulation of a thin 100 nm YHO coating is below 10% thus having high transmittance throughput while allowing for solar cell life-time saving by removal of excess irradiance. Finally, the surface energy of the YHO coated glass structures are presented, demonstrating synergetic chemical and structural (the Lotus effect), showing promising self-cleaning properties. In conclusion, we show possibilities to combine photonic and chromogenic principles with suitable surface chemistry to achieve high-performance cover glass for solar energy application. ., Funding: Energimyndigheten P2022-00859, Transparenta multifunktionella tunnfilmer på lågjärnglas för solcellsapplikationer, Semi-transparent solcells- och fotokromt smart fönster

We study the influence of nonlocal damping on the magnon properties of Fe, Co, Ni, and Fe1-xCox (x=30%,50%) alloys. The Gilbert damping parameter is typically considered as a local scalar both in experiment and in theoretical modeling. However, recent works have revealed that Gilbert damping is a nonlocal quantity that allows for energy dissipation between atomic sites. With the Gilbert damping parameters calculated from a state-of-the-art real-space electronic structure method, magnon lifetimes are evaluated from spin dynamics and linear response, where a good agreement is found between these two methods. It is found that nonlocal damping affects the magnon lifetimes in different ways depending on the system. Specifically, we find that in Fe, Co, and Ni, the nonlocal damping decreases the magnon lifetimes, while in Fe70Co30 and Fe50Co50 an opposite, nonlocal damping effect is observed, and our data show that it is much stronger in the former.

Many-electron systems undergo a collective Larmor precession in the presence of a magnetic field. In a paramagnetic metal, the resulting spin wave provides insight into the correlation effects generated by the electron-electron interaction. Here, we use dynamical mean-field theory to investigate the collective Larmor precession in the strongly correlated regime, where dynamical correlation effects such as quasiparticle lifetimes and non-quasiparticle states are essential. We study the spin excitation spectrum, which includes a dispersive Larmor mode as well as electron-hole excitations that lead to Stoner damping. We also extract the momentum-resolved damping of slow spin waves. The accurate theoretical description of these phenomena relies on the Ward identity, which guarantees a precise cancellation of self-energy and vertex corrections at long wavelengths. Our findings pave the way towards a better understanding of spin wave damping in correlated materials.

The unconventional superconductor Sr2RuO4 has long served as a benchmark for theories of correlated-electron materials. The determination of the superconducting pairing mechanism requires detailed experimental information on collective bosonic excitations as potential mediators of Cooper pairing. We have used Ru L3-edge resonant inelastic x-ray scattering to obtain comprehensive maps of the electronic excitations of Sr2RuO4 over the entire Brillouin zone. We observe multiple branches of dispersive spin and orbital excitations associated with distinctly different energy scales. The spin and orbital dynamical response functions calculated within the dynamical mean-field theory are in excellent agreement with the experimental data. Our results highlight the Hund metal nature of Sr2RuO4 and provide key information for the understanding of its unconventional superconductivity.

Neuromorphic computing mimics the brain's architecture to create energy-efficient devices. Reconfigurable synapses are crucial for neuromorphic computing, which can be achieved through memory-resistive (memristive) switching. Graphene-based memristors have shown nonvolatile multibit resistive switching with desirable endurance. Through first-principles calculations, we study the structural and electronic properties of graphene in contact with an ultra-thin alumina overlayer and demonstrate how one can use charge doping to exert direct control over its interfacial covalency, reversibly switching between states of conductivity and resistivity in the graphene layer. We further show that this proposed mechanism can be stabilized through the p-type doping of graphene, e.g., by naturally occurring defects, the passivation of dangling bonds or defect engineering.

We report the existence of entangled steady-states in bipartite quantum magnonic systems at elevated temperatures. We consider dissipative dynamics of two magnon modes in a bipartite antiferromagnet, subjected to interaction with a phonon mode and an external rotating magnetic field. To quantify the bipartite magnon-magnon entanglement, we use entanglement negativity and compute its dependence on temperature and magnetic field. We provide evidence that the coupling between magnon and phonon modes is necessary for the entanglement, and that, for any given phonon frequency and magnon-phonon coupling rate, there are always ranges of the magnetic field amplitudes and frequencies for which magnon-magnon entanglement persists at room temperature., The authors acknowledge financial support from the Knut and Alice Wallenberg Foundation through Grants No. 2018.0060 and No. 2021.0246. A Bergman and O E acknowledges eSSENCE. A D acknowledges financial support from the Swedish Research Council (VR) through Grants No. 2019-05304 and 2016-05980. O E acknowledges support by the Swedish Research Council (VR), the Foundation for Strategic Research (SSF), the European Research Council (854843-FASTCORR) and STandUP. D T acknowledges support from the Swedish Research Council (VR) with Grant No. 2019-03666. Y L acknowledges financial support from the KTH-CSC scholarship agreement (No. 201907090094). E S acknowledges financial support from the Swedish Research Council (VR) through Grant No. 2017-03832.

The detection of magnons and their quantum properties, especially in antiferromagnetic (AFM) materials, is a substantial step to realize many ambitious advances in the study of nanomagnetism and the development of energy efficient quantum technologies. The recent development of hybrid systems based on superconducting circuits provides the possibility to engineer quantum sensors that exploit different degrees of freedom. Here, we examine the magnon-photon-transmon hybridization based on bipartite AFM materials, which gives rise to an effective coupling between a transmon qubit and magnons in a bipartite AFM. We demonstrate how magnon modes, their chiralities, and quantum properties, such as nonlocality and two-mode magnon entanglement in bipartite AFMs, can be characterized through the Rabi frequency of the superconducting transmon qubit., The authors acknowledge financial support from the Knut and Alice (KAW) foundation through Grants No. 2018.0060 and No. 2021.0246. A.D. acknowledges financial support from the Swedish Research Council (VR) through Grants No.2016-05980 and No. 2019-05304 as well as the Knut and Alice (KAW) foundation through Grant No. 2022.0108. O.E .acknowledges support from the Swedish Research Council (VR), the Swedish Foundation for Strategic Research (SSF), the Swedish Energy Agency (Energimyndigheten), ERC (synergy grant FASTCORR, Project No. 854843), eSSENCE, and STandUPP. D.T. acknowledges support from the Swedish Research Council (VR) through Grant No. 2019-03666. E.S. acknowledges financial support from the Swedish Research Council (VR) through Grant No. 2017-03832. Some of the computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Center (NSC), Linköping University, the PDC Centre for High Performance Computing (PDC-HPC), KTH, and the High Performance Computing Center North (HPC2N), Umeå University.

Understanding the low-temperature properties of strongly correlated materials requires accurate measurement of the physical properties of these systems. Specific heat and nuclear spin-lattice relaxation are two such properties that allow the investigation of the electronic behavior of the system. In this thesis, nanocalorimetry is used to measure specific heat, but also as basis for new experimental approach, developed to disentangle the different contributions to specific heat at low temperatures. The technique, that we call Thermal Impedance Spectroscopy (TISP) allows independent measurement of the electronic and nuclear specific heat at low temperatures based on the frequency response of the calorimeter-sample assembly. The method also enables simultaneous measurements of the nuclear spin-lattice relaxation time (T1). The nuclear spin lattice relaxation, as 1/T1T, and electronic specific heat, as C/T, provide information about the same quantity, electronic density of states, in the system. By comparing these properties in strongly correlated systems, we can obtain insights of electronic interactions. Metallic indium is studied using thermal impedance spectroscopy from 0.3 K to 7 K at 35 T. The magnetic field dependence of nuclear spin-lattice relaxation rate is measured. Indium is a simple metallic system and the expected behavior of the nuclear spin-lattice relaxation is similar to that of the electronic specific heat. The results of the measurement are matched with the expectation from a simple metallic system and Nuclear Magnetic Resonance (NMR) measurements. This demonstrates the effectiveness of the new technique. The heavy-fermion superconductor CeCoIn5 is studied using thermal impedance spectroscopy and ac-calorimetry. This material is located near a quantum critical point (QCP) bordering antiferromagnetism, as evidenced by doping studies. The nature of its quantum criticality and unconventional superconductivity is still elusive. Contrasting specific h

Semiconducting nanowires (NWs) fabricated from III-V materials have gained significant attention for their application in advanced optoelectronic devices. Here, the growth of GaAs/GaInNAs/GaAs core-multishell NWs with a triple quantum-well structure, having about 2% N and 20% In, is reported. The NWs are grown via selective area plasma-assisted molecular beam epitaxy on patterned Si(111) substrates with SiO2 mask holes. The nucleation and growth of the GaAs nanowires core are carried out by Ga-induced vapor-liquid-solid growth at the open holes. Finely controlled, vertically aligned, regular core-multishell NWs with uniform wire length and diameter are obtained with a 96% yield and targeted nitrogen concentrations of 0%, 2%, and 3%. The GaInNAs NWs exhibit a spectral red shift relative to the GaAs NWs peak. Their emission wavelength increases with the N content reaching up to 1.26 mu m, which makes them a promising tool in telecommunication light sources., Funding Agencies|Japan Society for the Promotion of Science [16H05970, 19H00855, 21KK0068, 23H00250]; Advanced Research Infrastructure for Materials and Nanotechnology in Japan (ARIM) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT) [22UT1160]; Swedish Foundation for International Cooperation in Research and Higher Education (STINT) [JA2014-5698]; Swedish Research Council [2019-04312]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

We have performed a comprehensive, first-principles high-throughput study of the magnetic properties of halide double perovskites, Cs2BBCl-6, with magnetic ions occupying one or both B and B sites. Our findings indicate a general tendency for these materials to exhibit antiferromagnetic ordering with low Neel temperatures. At the same time, we reveal a few potential candidates that predicted to be ferromagnetic with relatively high Curie temperatures. Achieving ferromagnetic coupling might be feasible via simultaneously alloying at B and B sites with magnetic 3d and nonmagnetic 5d ions. With this approach, we discover that Cs2HgCrCl6, Cs2AgNiCl6, and Cs2AuNiCl6 have high Curie temperatures relative to their peers, with the latter two exhibiting half metallic behavior. Further, this study illuminates the underpinning mechanism of magnetic exchange interactions in halide double perovskites, enabling a deeper understanding of their magnetic behavior. Our findings, especially the discovery of the compounds with robust half metallic properties and high Curie temperatures, hold promise for potential applications in the field of spintronics., Funding Agencies|Knut and Alice Wallenberg Foundation [KAW 2019.0082]; Swedish Government Strategic Research Areas in Materials Science on Functional Materials at Linkoeping University [2009-00971]; Swedish Research Council [2019-05551, 854843, KAW-2018.0194]; ERC [2022-06725]; Wallenberg [2018-05973]

Carbon nitrides featuring three-dimensional frameworks of CN4 tetrahedra are one of the great aspirations of materials science, expected to have a hardness greater than or comparable to diamond. After more than three decades of efforts to synthesize them, no unambiguous evidence of their existence has been delivered. Here, the high-pressure high-temperature synthesis of three carbon-nitrogen compounds, tI14-C3N4, hP126-C3N4, and tI24-CN2, in laser-heated diamond anvil cells, is reported. Their structures are solved and refined using synchrotron single-crystal X-ray diffraction. Physical properties investigations show that these strongly covalently bonded materials, ultra-incompressible and superhard, also possess high energy density, piezoelectric, and photoluminescence properties. The novel carbon nitrides are unique among high-pressure materials, as being produced above 100 GPa they are recoverable in air at ambient conditions.

Metal halide perovskites are an emerging materials platform for optoelectronic, spintronic, and thermoelectric applications. The field of perovskite materials and devices has progressed rapidly over the past decade. For halide perovskite materials, a range of physical and chemical properties such as crystal structure, bandgap, charge carrier density, and stability that govern the device functionalities are critically determined by the oxidation states of the B-site metal ions. However, such an important mechanistic connection unique to halide perovskites is not well established, limiting the pace of development in this area. In this review, we identify the roles of metal oxidation states in perovskite semiconductors. The redox reactions leading to these states, and their effects on the materials properties, are clarified. Finally, we suggest routes to improving device efficiency and stability from the perspective of oxidation state control., Funding Agencies|National Key Research and Development Program of China [2022YFA1204800]; National Natural Science Foundation of China (NSFC) [61975180, 62274144, 62005243]; Kun-Peng Programme of Zhejiang Province; Natural Science Foundation of Zhejiang Province [LR21F050003]; Zhejiang University Education Foundation Global Partnership Fund; Knut and Alice Wallenberg Foundation [KAW 2019.0082]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Chao -Yong Postdoctoral Fellowship Program of International Campus, Zhejiang University

Circularly polarized light sources with free-space directional emission play a key role in chiroptics1, spintronics2, valleytronics3 and asymmetric photocatalysis4. However, conventional approaches fail to simultaneously realize pure circular polarization, high directionality and large emission angles in a compact emitter. Metal-halide perovskite semiconductors are promising light emitters5,6,7,8, but the absence of an intrinsic spin-locking mechanism results in poor emission chirality. Further, device integration has undermined the efficiency and directionality of perovskite chiral emitters. Here we realize compact spin-valley-locked perovskite emitting metasurfaces where spin-dependent geometric phases are imparted into bound states in the continuum via Brillouin zone folding, and thus, photons with different spins are selectively addressed to opposite valleys. Employing this approach, chiral purity of 0.91 and emission angle of 41.0° are simultaneously achieved, with a beam divergence angle of 1.6°. With this approach, we envisage the realization of chiral light-emitting diodes, as well as the on-chip generation of entangled photon pairs.