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Uniquely, large-bipolarons' self-trapped holes occupy superoxygens, each comprising four oxygens circumscribed by four coppers in a CuO2 plane, formed as oxygens relax inward and coppers relax outward. Critically, concomitant oxygen-to-copper electron transfer eliminates copper spins. The d-symmetry of superoxygens' ground state molecular orbital tracks the superoxygens' predominant zero-point radial vibrations. These large bipolarons' distinctive charge transport, absorption, magnetism, local atomic vibrations, condensation into a liquid, and subsequent superconductivity are consistent with cuprate superconductors' long-established unusual properties. [ABSTRACT FROM AUTHOR]

To obtain high-performance THz-wave-emitting devices made of single crystals of Bi 2 Sr 2 CaCu 2 O 8 + δ (Bi2212), a high-temperature superconductor, an understanding of the device characteristics based on crystal characteristics can be a key issue because, in principle, the electrical properties of the intrinsic Josephson junctions (IJJs) constructed in Bi2212 crystals highly depend on crystal conditions, such as carrier concentration, crystal homogeneities, and crystal defects. To evaluate the tendencies of the device characteristics associated with crystal characteristics, we prepared Bi2212 crystals with different Bi/Sr ratios (x = 0.05 , 0.15, and 0.25) and δ values (annealed under N 2 or O 2 gas flow conditions). The unit cell parameter c decreased as the Bi/Sr ratio or δ increased. For the same annealing conditions under N 2 gas flow, the superconducting transition temperature as well as the size of the hysteresis loop of the current–voltage characteristics and emission characteristics were significantly suppressed for the sample with x = 0.25 compared with the corresponding values for the samples with x = 0.05 and 0.15. The experimental results clearly indicate that parameters, such as the Bi/Sr ratio and annealing conditions, are crucial factors in determining the electrical characteristics of a device. This information can be a useful guide for the preparation of crystals for IJJ THz-wave devices that can be fine-tuned according to the desired device characteristics. [ABSTRACT FROM AUTHOR]

The enigmatic mechanism underlying unconventional high-temperature superconductivity, especially the role of lattice dynamics, has remained a subject of debate. Theoretical insights have long been hindered due to the lack of an accurate first-principles description of the lattice dynamics of cuprates. Recently, using the r2SCAN meta-generalized gradient approximation (meta-GGA) functional, we have been able to achieve accurate phonon spectra of an insulating cuprate YBa2Cu3O6 and discover significant magnetoelastic coupling in experimentally interesting Cu–O bond stretching optical modes [Ning et al., Phys. Rev. B 107, 045126 (2023)]. We extend this work by comparing Perdew–Burke–Ernzerhof and r2SCAN performances with corrections from the on-site Hubbard U and the D4 van der Waals (vdW) methods, aiming at further understanding on both the materials science side and the density functional side. We demonstrate the importance of vdW and self-interaction corrections for accurate first-principles YBa2Cu3O6 lattice dynamics. Since r2SCAN by itself partially accounts for these effects, the good performance of r2SCAN is now more fully explained. In addition, the performances of the Tao–Mo series of meta-GGAs, which are constructed in a different way from the strongly constrained and appropriately normed (SCAN) meta-GGA and its revised version r2SCAN, are also compared and discussed. [ABSTRACT FROM AUTHOR]

The enigmatic mechanism underlying unconventional high-temperature superconductivity, especially the role of lattice dynamics, has remained a subject of debate. Theoretical insights have long been hindered due to the lack of an accurate first-principles description of the lattice dynamics of cuprates. Recently, using the r2SCAN meta-generalized gradient approximation (meta-GGA) functional, we have been able to achieve accurate phonon spectra of an insulating cuprate YBa2Cu3O6 and discover significant magnetoelastic coupling in experimentally interesting Cu–O bond stretching optical modes [Ning et al., Phys. Rev. B 107, 045126 (2023)]. We extend this work by comparing Perdew–Burke–Ernzerhof and r2SCAN performances with corrections from the on-site Hubbard U and the D4 van der Waals (vdW) methods, aiming at further understanding on both the materials science side and the density functional side. We demonstrate the importance of vdW and self-interaction corrections for accurate first-principles YBa2Cu3O6 lattice dynamics. Since r2SCAN by itself partially accounts for these effects, the good performance of r2SCAN is now more fully explained. In addition, the performances of the Tao–Mo series of meta-GGAs, which are constructed in a different way from the strongly constrained and appropriately normed (SCAN) meta-GGA and its revised version r2SCAN, are also compared and discussed. [ABSTRACT FROM AUTHOR]

Cd2+ cation doped CsPbCl3 single crystals were synthesized, and their luminescent properties were investigated under excitation with synchrotron radiation quanta with energy greater than Eg and at a sample temperature of 12 K. Pure single crystals exhibit a narrow band of exciton emission at 416.7 nm. Doping the single crystals leads to a high-energy shift of the excitonic luminescence, the appearance of new luminescent bands, the broadening of the luminescent bands, an increase in the decay time constants, and a significant enhancement of the luminescence intensity. The observed changes in luminescent parameters upon doping are discussed in terms of the crystal structure ordering, a decrease in the number of defects responsible for capturing charge carriers at the stage of electronic excitation thermalization, and a decrease in defects that quench excitonic luminescence. Doped single crystals with decay times of the order of 0.4 ns and intensities that significantly exceed the intensity of pure single crystals can be promising scintillation materials for positron emission tomography in the time-of-flight mode. [ABSTRACT FROM AUTHOR]

GdI 2 monolayer is a promising material for spintronics applications due to its robust room-temperature ferromagnetism and sizable valley polarization. In two-dimensional van der Waals magnets, interlayer magnetic coupling plays a crucial role in device applications. The performance of these devices can be effectively tuned by adjusting the stacking order, charge doping, and strain. By performing first-principles calculations, we have demonstrated that the interlayer magnetic coupling in bilayer GdI 2 is highly dependent on the stacking order, which can be tuned between ferromagnetic (FM) and antiferromagnetic orders through lateral shifting. Furthermore, the interlayer magnetic coupling can also be tuned by charge doping and strain, where both electron and hole doping can enhance the FM coupling interaction between layers, and the interlayer FM coupling can be strengthened with increasing biaxial tensile strain. These results show that bilayer GdI 2 has rich tunable interlayer magnetic interactions, which can be used in designing interesting spin tunnel field-effect transistor devices. [ABSTRACT FROM AUTHOR]

GdI 2 monolayer is a promising material for spintronics applications due to its robust room-temperature ferromagnetism and sizable valley polarization. In two-dimensional van der Waals magnets, interlayer magnetic coupling plays a crucial role in device applications. The performance of these devices can be effectively tuned by adjusting the stacking order, charge doping, and strain. By performing first-principles calculations, we have demonstrated that the interlayer magnetic coupling in bilayer GdI 2 is highly dependent on the stacking order, which can be tuned between ferromagnetic (FM) and antiferromagnetic orders through lateral shifting. Furthermore, the interlayer magnetic coupling can also be tuned by charge doping and strain, where both electron and hole doping can enhance the FM coupling interaction between layers, and the interlayer FM coupling can be strengthened with increasing biaxial tensile strain. These results show that bilayer GdI 2 has rich tunable interlayer magnetic interactions, which can be used in designing interesting spin tunnel field-effect transistor devices. [ABSTRACT FROM AUTHOR]

The connection between the long-range antiferromagnetic order in cuprates and the high-temperature superconductivity is a scientific problem that has yet to be solved after nearly four decades. The properties and difficulties of describing nickelate superconductors are similar to those of cuprates. Recently, Fowlie et al. [Nat. Phys. 18, 1043 (2022)] aimed to detect the antiferromagnetic order in R1−xSrxNiO2 (R = Nd, Pr, La; x ∼ 0, 0.2) films by using the muon spin rotation (μSR) technique. The research group reported the presence of short-range antiferromagnetic order in every nickelate studied. Here, our goal was to prove that this interaction is present in the nickelate films. We did this by analyzing the temperature dependent resistivity, ρ(T), data from the research group. Global ρ(T) data fits to the advanced Bloch–Grüneisen model showed that each of the R1−xSrxNiO2 compounds can be characterized by a unique power-law exponent, p (where p = 2 for the electron–electron scattering, p = 3 for the electron–magnon scattering, and p = 5 for the electron–phonon scattering), and global characteristic temperature, Tω (which has the meaning of the Debye temperature at p = 5). We found that p = 2.0 in Nd- and Pr-based compounds and p = 1.3 for La-based compounds. The latter value does not have any interpretation within established theoretical models. We also analyzed ρ(T) data for Nd1–xSrxNiO2 (0.125 ≤ x ≤ 0.325) reported by Lee et al. [Nature 619, 288 (2023)]. Our analysis of nickelates led us to conclude that a new theoretical model is needed to describe ρ(T) in materials exhibiting a short-range antiferromagnetic order. [ABSTRACT FROM AUTHOR]

We study the transport properties of underdoped trilayer cuprate HgBa2Ca2Cu3O8+δ with doping level p = 0.10–0.12 in magnetic field up to 88 T. We report for the first time in a cuprate superconductor a dramatic change of the quantum oscillation spectrum versus temperature, which is accompanied by a sign change of the Hall effect below T ≈10 K. Based on numerical simulations, we infer a Fermi surface reconstruction in the inner plane from an antiferromagnetic state (hole pockets) to a biaxial charge density wave state (electron pockets). We show that both orders compete and share the same hotspots of the Fermi surface, and we discuss our result in the context of spin-fermion models. [ABSTRACT FROM AUTHOR]

Yttrium barium copper oxide (YBCO) is used for special applications in linear generators because of its excitation loss, lower weight, and higher efficiency. These qualities enable the compound to operate better than the conventional copper wire coil in the stator unit of the linear generator. However, the continuous use of YBCO in linear generators has a fundamental challenge that affects industrial production and material stability after prolonged use. This paper seeks to sustain the adoption of YBCO by improving its quality for linear generator applications. The yttrium cuprates modification (YBYbCO) was synthesized using the solid-state reaction technique by doping YBCO with ytterbium. The crystalline structure, microstructural pattern, and stability of the new sample were adequately measured and found to be structurally stable to ensure durability. It was reported that applying YBYbCO in the linear generator would lead to a 200% increase in energy generation. The higher number of particles and lower individual particulate resistance enable it to withstand chemical pressure, thereby prolonging the lifespan of the linear generator. [ABSTRACT FROM AUTHOR]

A series of experimental studies established that the differing morphologies of the phase diagrams versus hole doping nh of the various cuprate families are mostly controlled by defects and disorder. In the minimally disordered cuprate Yttrium Baryum Copper Oxide (YBCO) we introduced controlled detfects that allowed us to probe the metallic and superconducting states. We demonstrate that the extent of the spin glass phase and the superconducting dome can be controlled by the concentration of spinless (Zn, Li) impurities substituted on the planar Cu sites. NMR frequency shift measurements establish that these defects induce, in their vicinity, a cloud with a Kondo-like paramagnetic behavior. Its "Kondo" temperature and spatial extent differ markedly between the pseudogap and strange metal regimes. We have performed transport measurements on single crystals with a controlled content of in-plane vacancies introduced by electron irradiation. At high T, the inelastic scattering of the carriers has been found independent of disorder and completely governed by the excitations of the correlated electronic state. The low T upturns in the resistivity associated with single-site Kondo-like scattering are qualitatively in agreement with local magnetism induced by spinless impurities. The apparent metal insulator crossover is only detected for a very large defect content, and part of the large resistivity upturn remains connected with Kondo-like paramagnetism. In the superconducting state, the defect-induced reduction of Tc scales linearly with the increase in residual resistivity induced by disorder. High-field magnetoresistance experiments permit us to determine the paraconductivity due to superconducting fluctuations. The latter vanishes beyond a temperature T'c and a field H'c that both decrease with increasing in-plane defect content. In the pseudogap regime, the weaker decrease of T'c with respect to that of Tc reveals a large loss of superconducting phase coherence in the presence of disorder. In light of our experimental results, we initiate a discussion of its interplay with pair breaking. Our data also permit us to confirm that the differing phase diagrams are due to competing orders or disorders that are family-specific. In the ideal phase diagram of a disorder-free cuprate, 2D superconductivity should persist at low doping. This ensemble of experimental results provides serious challenges for the theoretical understanding of superconductivity in these correlated electron systems. [ABSTRACT FROM AUTHOR]

We investigated the effect of 0.6 MeV proton irradiation on the superconducting and normal-state properties of thin-film YBa 2 Cu 3 O 7 − δ superconductors. A thin-film YBCO superconductor (≈567 nm thick) was subject to a series of proton irradiations with a total fluence of 7.6 × 10 16   p / cm 2 . Upon irradiation, T c was drastically decreased from 89.3 K towards zero with a corresponding increase in the normal-state resistivity above T c . This increase in resistivity, which indicates an increase in defects inside the thin-film sample, can be converted to the dimensionless scattering rate. We found that the relation between T c and the dimensionless scattering rate obtained during proton irradiation approximates the generalized d-wave Abrikosov–Gor'kov theory better than the previous results obtained from electron irradiations. This is an unexpected result, since the electron irradiation is known to be most effective to suppress superconductivity over other heavier ion irradiations such as proton irradiation. In comparison with the previous irradiation studies, we found that the result can be explained by two facts. First, the dominant defects created by 0.6 MeV protons can be point-like when the implantation depth is much longer than the sample thickness. Second, the presence of defects on all element sites is important to effectively suppress T c . [ABSTRACT FROM AUTHOR]

While closing their famous paper entitled "Pseudogap: friend or foe of high-Tc?" Norman, Pines, and Kallin underlined that before we have a microscopic theory, we must have a consistent phenomenology. This was in 2005. As it turns out in 2006, a phenomenological theory of the pseudogap state was proposed by Gor'kov and Teitel'baum. This originated from their careful analysis of the Hall effect data, and it has been very successful model as numerous investigations over the years have shown. In this mini-review, the essence of the idea of Gor'kov and Teitel'baum is presented. The pseudogap obtained by them from the Hall effect data agrees very well with that obtained from the ARPES data. This famous Gor'kov–Teitel'baum thermal activation model (in short GTTA model) not only presents a consistent phenomenology of the pseudogap state, but also rationalizes the Hall angle data, and it presents a strong case against the famous "two-relaxation times" idea of Anderson and collaborators. [ABSTRACT FROM AUTHOR]

Superconducting magnets based on high-temperature superconductors (HTSs) have become critical components in cutting-edge technologies such as advanced medical applications. In HTSs, weak links of superconductivity are inevitable at high-angle grain boundaries (GBs). Thus, two adjacent grains should be crystallographically aligned within the critical angle (θc), for which the intergrain critical current density (Jc) starts to decrease exponentially. The θc of several iron-based superconductors (IBSs) is larger than that of cuprates. However, the decreases in both θc and intergrain Jc under magnetic fields for IBSs are still substantial, hampering their applications in polycrystalline forms. Here, we report that potassium-doped BaFe2As2 (Ba122:K) exhibits superior GB performance to that of previously reported IBSs. A transport Jc of over 0.1 MA/cm2 across [001]-tilt GBs with misorientation angles up to θGB = 24° was recorded even at 28 K, which is a required level for practical applications. Additionally, even in an applied magnetic field, θc was unaltered, and the decay of the intergrain Jc was small. Our results highlight the exceptional potential of Ba122:K for polycrystalline applications and pave the way for next-generation superconducting magnets. We have fabricated artificial grain boundaries in K-doped BaFe2As2 (Ba122:K), one of the Fe-based superconductors. The crystalline orientation map, acquired through the scanning precession electron diffraction measurements, revealed that spontaneous connectivity modification occurred at the grain boundary, which may mitigate weak-link behavior. Specifically, a self-field critical current density Jc of over 0.1 MA/cm2 across the grain boundary with misorientation angles up to 24° was recorded even at 28 K. This performance surpasses the grain boundary properties of hitherto reported Fe-based superconductors. Our results highlight the exceptional potential of Ba122:K for polycrystalline applications and pave the way for next-generation superconducting magnets. [ABSTRACT FROM AUTHOR]

In the underdoped n-type cuprate Nd2-xCexCuO4, long-range antiferromagnetic order reconstructs the Fermi surface, resulting in a putative antiferromagnetic metal with small Fermi pockets. Using angle-resolved photoemission spectroscopy, we observe an anomalous energy gap, an order of magnitude smaller than the antiferromagnetic gap, in a wide portion of the underdoped regime and smoothly connecting to the superconducting gap at optimal doping. After considering all the known ordering tendencies in tandem with the phase diagram, we hypothesize that the normal-state gap in the underdoped n-type cuprates originates from Cooper pairing. The high temperature scale of the normal-state gap raises the prospect of engineering higher transition temperatures in the n-type cuprates comparable to those of the p-type cuprates. [ABSTRACT FROM AUTHOR]

Strongly correlated electron materials are often characterized by competition and interplay of multiple quantum states. For example, in high-temperature cuprate superconductors unconventional superconductivity, spin- and charge-density wave orders coexist. A key question is whether competing states coexist on the atomic scale or if they segregate into distinct regions. Using X-ray diffraction, we investigate the competition between charge order and superconductivity in the archetypal cuprate La2−xBaxCuO4, around x = 1/8-doping, where uniaxial stress restores optimal 3D superconductivity at σ3D ≈ 0.06 GPa. We find that the charge order peaks and the correlation length along the stripe are strongly reduced up to σ3D. Upon the increase of stress beyond this point, no further changes were observed. Simultaneously, the charge order onset temperature only shows a modest decrease. Our findings suggest that optimal 3D superconductivity is not linked to the absence of charge stripes but instead requires their arrangement into smaller regions. Our results provide insight into the length scales over which the interplay between superconductivity and charge order takes place. In many quantum materials, different electronic phases can coexist or compete with one another. In this work uniaxial pressure is used to achieve the spatial distribution of charge order that maximizes the superconducting transition temperature. [ABSTRACT FROM AUTHOR]

Superconducting infinite-layer (IL) nickelates offer a new platform for investigating the long-standing problem of high-temperature superconductivity. Many models were proposed to understand the superconducting mechanism of nickelates based on the calculated electronic structure, and the multiple Fermi surfaces and multiple orbitals involved create complications and controversial conclusions. Over the past five years, the lack of direct measurements of the electronic structure has hindered the understanding of nickelate superconductors. Here we fill this gap by directly resolving the electronic structures of the parent compound LaNiO2 and superconducting La0.8Ca0.2NiO2 using angle-resolved photoemission spectroscopy. We find that their Fermi surfaces consist of a quasi-2D hole pocket and a 3D electron pocket at the Brillouin zone corner, whose volumes change upon Ca doping. The Fermi surface topology and band dispersion of the hole pocket closely resemble those observed in hole-doped cuprates. However, the cuprate-like band exhibits significantly higher hole doping in superconducting La0.8Ca0.2NiO2 compared to superconducting cuprates, highlighting the disparities in the electronic states of the superconducting phase. Our observations highlight the novel aspects of the IL nickelates, and pave the way toward the microscopic understanding of the IL nickelate family and its superconductivity. [ABSTRACT FROM AUTHOR]

Information on the state of research on the effect of hydrogen on the superconducting properties of various compounds is presented. The review consists of an introduction, one appendix and four sections: methods for the synthesis of modern hydrogen-containing superconductors, experimental studies of the properties of hydrogen-containing superconductors, mechanisms of the influence of hydrogen on superconductivity, problems and prospects of hydrogen-containing superconductors. [ABSTRACT FROM AUTHOR]

Extensive research on transition metal perovskite oxides as electrodes in solid oxide cells (SOC) has highlighted the potential ability of Fe-based perovskite oxides to catalyze oxygen reduction/evolution reactions (ORR/OER). The layered perovskite-type system YSr2Cu2FeO7+δ has been reported to possess attractive electrocatalytic properties. This work applies density functional theory (DFT) calculations to investigate oxygen ion diffusion in the YSr2Cu2FeO7+δ system. For δ = 0.5, it is found that in the most stable configuration, the oxygen vacancies in the FeO1+δ plane are arranged to form Fe ions in tetrahedral, square pyramid, and octahedral coordination. Ab initio molecular dynamics (AIMD) simulations for YSr2Cu2FeO7.5 (δ = 0.5) yield an oxygen ion diffusion coefficient of 1.28 × 10−7 cm2/s at 500 °C (Ea = 0.37 eV). Complementary results for YSr2Cu2FeO7.2 (δ = 0.2) and YSr2Cu2FeO7.75 (δ = 0.75) indicate that the oxygen diffusion occurs in the FeO1+δ plane, and depends on the oxygen vacancies distribution around the Fe centers. [ABSTRACT FROM AUTHOR]

SmNiO 3 is a representative quantum material exhibiting the antidoping behavior, where the conductivity of the material is reduced rather than increased by electron doping. Recent experimental and theoretical works have demonstrated a phase transition of SmNiO 3 with large conductance changes via chemical methods. However, the effect of electron doping via interfacial charge transfer in SmNiO 3 is much less studied. In this work, the first-principles density functional theory (DFT)+ U method is employed to investigate the SmNiO 3 /YTiO 3 superlattice, in which the YTiO 3 layer acts as the electron donor. Compared with the chemical doping in SmNiO 3 , several interesting physical phenomena have been predicted in SmNiO 3 /YTiO 3 superlattices due to the lattice and electronic reconstructions. First, at a doping concentration of 1 e − per Ni, i.e., (SmNiO 3) 1 /(YTiO 3) 1 superlattice, all Ni 3 + are converted to Ni 2 + , resulting in a Mott-insulating phase, similar to the chemical doping in the pristine material. Interestingly, such a Mott gap can be efficiently modulated by tuning the stacking orientation. Second, at a doping concentration of 1 2 e − per Ni, i.e., [ 001 ]-orientated (SmNiO 3) 2 /(YTiO 3) 1 superlattice, the electronic structure associated with charge ordering depends on the concrete magnetic order, giving rise to magnetism-dependent electronic behavior. In addition, as the doping concentration further decreases (i.e., a doping concentration of 1 3 e − /Ni), a metallic state is predicted in a [ 001 ]-orientated (SmNiO 3) 3 /(YTiO 3) 1 superlattice, which is quite different from the case of chemical doping. [ABSTRACT FROM AUTHOR]

Spin- and charge- stripe order has been extensively studied in the superconducting cuprates, among which underdoped La2−xSrxCuO4 (LSCO) is an archetype with static spin stripes at low temperatures. An intriguing, but not completely understood, phenomenon in LSCO is that the stripes are tilted away from the high-symmetry Cu-Cu directions. Using high-resolution neutron scattering on LSCO with x = 0.12, we find two coexisting phases at low temperatures, one with static spin stripes and the other with fluctuating ones, both sharing the same tilt angle. Our numerical calculations using the doped Hubbard model elucidate the tilting's origin, attributing it to anisotropic next-nearest neighbor hopping t ′ , consistent with the material's slight orthorhombicity. Our results underscore the model's success in describing specific details of the ground state of this real material and highlight the role of t ′ in the Hamiltonian, revealing the delicate interplay between stripes and superconductivity across theoretical and experimental contexts. Cuprate superconductors have interesting charge and spin ordering patterns in the form of stripes. By combining experimental and numerical tools, the authors reveal that the stripes are always tilted from the underlying lattice directions, with the origin well explained by the anisotropy of the next-nearest neighbor electron hopping. [ABSTRACT FROM AUTHOR]

The low-temperature electrical transport in the normal-state of overdoped cuprate superconductors is investigated based on the t-J model. The momentum relaxation due to the umklapp scattering between electrons by the exchange of the effective spin propagator is employed to evaluate the electrical resistivity within the framework of the Boltzmann transport theory. It is shown that the quadratic temperature dependence of the resistivity develops in the far-lower-temperature region, and is followed by a nonlinear temperature dependence of the resistivity in an extremely-narrow-crossover region and a linear temperature dependence of the resistivity in the low-temperature region. The obtained results also show that the same spin excitation governs both superconductivity and the electron umklapp scattering responsible for the low-temperature linear in temperature resistivity in the overdoped regime. [ABSTRACT FROM AUTHOR]

The interfaces between superconductors and other materials have long been established as being an important part in the exploration of new physics to aid in our understanding of superconductivity and open us up to new technological advancements. Herein this article we analyse the recent progress made in the understanding of superconductivity at the interfaces involving a wide range of functional materials, mostly looking at two-dimensional (2D) systems. We start off in the first half of this review by focusing on magnetic and superconductive hybrid heterostructures, as well as the resulting physical phenomena from these systems. The first is a section on vortex and anti-vortex phenomena; the second key area is ferromagnet–superconductor hybrid phenomena with particular interest of magnetic skyrmions, the third is the novel frontier based on 2D magnetic and superconductive interfaces particularly examining Ising superconductivity at these interfaces; the fourth is superconductivity at anti-ferromagnetic interfaces and finally half-metals at superconducting interfaces. The second half of this review focuses on superconductivity at insulating and other functional interfaces. Examining firstly, Mott insulator interfaces with wide ranging discussions about how such interfaces can enhance our understanding in high-temperature superconductive cuprates and other unconventional superconductor systems such as the nickelates; in the second section the interface of 2D and 3D ferroelectric materials with superconductors with a key emphasis on devices that have been developed to control the superconducting phase; Topological insulators at interfaces with superconductors is the third section; and lastly 2D twisted material interfaces are explored, including the newly discovered magic angle interfaces discovered with graphene and other van Der Waals materials. It is anticipated that this review will lead to further interest in such interfaces to improve our understanding and expose the exotic science behind these interfaces. [Display omitted] [ABSTRACT FROM AUTHOR]

Unconventional superconductivity on a honeycomb lattice has received increasing interest since the discovery of graphene primarily due to the similarities between materials with a honeycomb lattice and cuprate superconductors. Many theoretical studies have been conducted on superconductivity on a honeycomb lattice, however, a consistent picture is still lacking. In this paper, we have extended the theory of kinetic-energy-driven superconductivity, which has been developed to investigate unconventional superconductivity in cuprate superconductors, to explore superconductivity on a honeycomb lattice within the t-J model. Our results demonstrate that the charge-carrier pair gap parameter with d x 2 − y 2 + i d x y -wave symmetry exhibits a dome-like shape as a function of doping, with superconductivity emerging at a certain doping concentration and disappearing at high doping levels, similar to what has been observed in cuprate and cobaltate superconductors. Furthermore, the charge-carrier pair gap parameter decreases with increasing the value of J ∕ t (the ratio between the antiferromagnetic exchange coupling constant and the nearest-neighbor hopping integral), and approaches zero when J ∕ t reaches a sufficiently large value. This indicates that the antiferromagnetic order will suppress the superconducting state and a sufficiently strong exchange coupling will completely destroy the superconductivity. Taking into account our present results together with the corresponding results of cuprate and cobaltate superconductors, it appears that the dome-like shape of the doping dependence of the charge-carrier pair gap parameter may be a common feature in doped Mott insulators. [ABSTRACT FROM AUTHOR]

Sr2IrO4 has attracted considerable attention due to its structural and electronic similarities to La2CuO4, the parent compound of high-Tc superconducting cuprates. It was proposed as a strong spin-orbit-coupled Jeff = 1/2 Mott insulator, but the Mott nature of its insulating ground state has not been conclusively established. Here, we use ultrafast laser pulses to realize an insulator-metal transition in Sr2IrO4 and probe the resulting dynamics using time-and angle-resolved photoemission spectroscopy. We observe a gap closure and the formation of weakly renormalized electronic bands in the gap region. Comparing these observations to the expected temperature and doping evolution of Mott gaps and Hubbard bands provides clear evidence that the insulating state does not originate from Mott correlations. We instead propose a correlated band insulator picture, where antiferromagnetic correlations play a key role in the gap opening. More broadly, our results demonstrate that energy-momentum-resolved nonequilibrium dynamics can be used to clarify the nature of equilibrium states in correlated materials. [ABSTRACT FROM AUTHOR]

We present a way to fabricate bicrystal Josephson junctions of high-Tc cuprate superconductors that are not grown on bulk bicrystalline substrates. Based on vector substrate technology, this approach makes use of a few tens-of-nanometer-thick bicrystalline membranes transferred onto conventional substrates. We demonstrate 24° [001]-tilt YBa2Cu3O7−x Josephson junctions fabricated on sapphire single crystals by utilizing 10-nm-thick bicrystalline SrTiO3 membranes. This technique allows one to manufacture bicrystalline Josephson junctions of high-Tc superconductors on a large variety of bulk substrate materials, providing distinctive degrees of freedom in designing the junctions and their electronic properties. Furthermore, it offers the capability to replace the fabrication of bulk bicrystalline substrates with thin-film growth methods. [ABSTRACT FROM AUTHOR]

Unconventional superconductivity often couples to other electronic orders in a cooperative or competing fashion. Identifying external stimuli that tune between these two limits is of fundamental interest. Here, we show that strain perpendicular to the copper-oxide planes couples directly to the competing interaction between charge stripe order and superconductivity in La1.88Sr0.12CuO4 (LSCO). Compressive c-axis pressure amplifies stripe order within the superconducting state, while having no impact on the normal state. By contrast, strain dramatically diminishes the magnetic field enhancement of stripe order in the superconducting state. These results suggest that c-axis strain acts as tuning parameter of the competing interaction between charge stripe order and superconductivity. This interpretation implies a uniaxial pressure-induced ground state in which the competition between charge order and superconductivity is reduced. Tuning superconductivity and its interplay with other phases in cuprates yields insights into the underlying physics of this material class. Here, the authors performed a hard x-ray diffraction experiment on La1.88Sr0.12CuO4 showing that uniaxial pressure along the c-axis acts as a direct tuning parameter of the competition between superconductivity and charge order. [ABSTRACT FROM AUTHOR]

Unconventional superconductivity often couples to other electronic orders in a cooperative or competing fashion. Identifying external stimuli that tune between these two limits is of fundamental interest. Here, we show that strain perpendicular to the copper-oxide planes couples directly to the competing interaction between charge stripe order and superconductivity in La1.88Sr0.12CuO4 (LSCO). Compressive c-axis pressure amplifies stripe order within the superconducting state, while having no impact on the normal state. By contrast, strain dramatically diminishes the magnetic field enhancement of stripe order in the superconducting state. These results suggest that c-axis strain acts as tuning parameter of the competing interaction between charge stripe order and superconductivity. This interpretation implies a uniaxial pressure-induced ground state in which the competition between charge order and superconductivity is reduced. Tuning superconductivity and its interplay with other phases in cuprates yields insights into the underlying physics of this material class. Here, the authors performed a hard x-ray diffraction experiment on La1.88Sr0.12CuO4 showing that uniaxial pressure along the c-axis acts as a direct tuning parameter of the competition between superconductivity and charge order. [ABSTRACT FROM AUTHOR]

We show that the temperature-dependent superconducting order parameter and related superconducting properties (in particular, the temperature dependences of specific heat, superfluid density and related London penetration depth) of high- T c cuprates are fundamentally different from those of conventional superconductors and cannot be understood within the existing theories based on the Bardeen–Cooper–Schrieffer (BCS)-type condensation of weakly bound Cooper pairs into a superfluid Fermi-liquid and on the usual Bose–Einstein condensation (BEC) of bosonic Cooper pairs. We examine the validity of an alternative approach to the unconventional superconductivity in high- T c cuprates and establish that these materials exhibiting a λ -like superconducting transition at the critical temperature T c are similar to the superfluid 4He and are also superfluid Bose systems. We argue that the doped high- T c cuprates, from underdoped to overdoped regime, are unconventional (bosonic) superconductors and the tightly bound (polaronic) Cooper pairs in these polar materials behave like composite bosons just like 4He atoms and condense into a Bose superfluid at T c . We identify the superconducting order parameter Δ SC in underdoped and optimally doped cuprates as the coherence parameter Δ B of bosonic Cooper pairs, which appears just below T c and has a kink-like temperature dependence near the characteristic temperature T c ∗ < T c . We find that the λ -like specific heat anomaly in high- T c cuprates near T c predicted by the theory of Bose-liquid superconductivity is similar to that observed both in superfluid 4He near T λ and in Hg-based cuprate superconductor HgBa2Ca2Cu3O8 near T c ≃ 1 3 2 K. We demonstrate that in high- T c superconductor YBa2Cu3 O 6. 9 7 the superfluid density ρ s exhibits distinctly different temperature dependences in the temperature ranges 0 ≤ T ≤ T c ∗ and T c ∗ < T < T c . In this superconductor, a pronounced anomaly in ρ s (T) exists near T c ∗ ≃ 0. 4 T c and the temperature dependence of λ L 2 (0) / λ L 2 (T) below T c ∗ deviates downwards from the high-temperature behavior. Our results for the normalized superfluid density ρ s (T) / ρ s (0) = λ L 2 (0) / λ L 2 (T) are in good agreement with the experimental data on the temperature dependence of λ L 2 (0) / λ L 2 (T) in YBa2Cu3 O 6. 9 7 . The anomalous temperature dependences of specific heat and superfluid density observed in Hg- and Y-based high- T c superconductors are clear signatures of Bose-liquid superconductivity. [ABSTRACT FROM AUTHOR]

Unconventional superconductivity often couples to other electronic orders in a cooperative or competing fashion. Identifying external stimuli that tune between these two limits is of fundamental interest. Here, we show that strain perpendicular to the copper-oxide planes couples directly to the competing interaction between charge stripe order and superconductivity in La1.88Sr0.12CuO4 (LSCO). Compressive c-axis pressure amplifies stripe order within the superconducting state, while having no impact on the normal state. By contrast, strain dramatically diminishes the magnetic field enhancement of stripe order in the superconducting state. These results suggest that c-axis strain acts as tuning parameter of the competing interaction between charge stripe order and superconductivity. This interpretation implies a uniaxial pressure-induced ground state in which the competition between charge order and superconductivity is reduced. Tuning superconductivity and its interplay with other phases in cuprates yields insights into the underlying physics of this material class. Here, the authors performed a hard x-ray diffraction experiment on La1.88Sr0.12CuO4 showing that uniaxial pressure along the c-axis acts as a direct tuning parameter of the competition between superconductivity and charge order. [ABSTRACT FROM AUTHOR]

The melt‐quenching technique is used to fabricate calcium sodium aluminum borate glasses (Sm: ANCB) doped with varying concentrations of Sm3+ ions. Characteristics of ANCBSm glasses, including density, molar volume, refractive index, absorption, emission (via visible light, X‐ray, and proton excitation), decay time, and CIE color coordinates, are analyzed. The density, molar volume, and refractive index of ANCBSm glass increased with Sm2O3 concentration. Sm3+ ions enabled photon absorption in both visible and NIR regions, with a strong reddish‐orange emission at 600 nm due to the 6H5/2 → 6P3/2 transition under various excitations. X‐ray excitation is also compared with BGO scintillation crystals. The J–O theory predicted the radiative properties of Sm3+ ion emission levels. Decay curves of the 6H5/2 levels showed a single exponential nature with a millisecond‐order lifetime. CIE chromaticity of ANCBSm glasses is in the reddish‐orange region. ANCBSm glasses have potential applications in orange laser medium material. [ABSTRACT FROM AUTHOR]

We demonstrate the optical response from high-Tc superconductor nanowires at temperatures above that of liquid nitrogen. Using hard oxide A l 2 O 3 as a mask material, we achieved miniaturized YB a 2 C u 3 O 7 − δ wires with widths nearing 100 nm, a significant milestone for highly sensitive photodetectors. We investigated the photoresponse of these nanowires at temperatures almost an order of magnitude higher than previously reported, under varying temperature and bias current conditions. Our findings reveal a strong correlation between the optical response and the critical parameters of the superconductor, with peak optical responses close to the critical values of temperature and bias current density. Nanowire response to wavelengths from visible to near-infrared range demonstrated a pronounced absorption maximum at temperatures below Tc. These results lay a solid foundation for the development of high-Tc superconductor nanowire single-photon detectors, understanding of nanoscale high-Tc superconductor structure optical behavior, and advancing the prospects of quantum technologies. [ABSTRACT FROM AUTHOR]

Unconventional superconductivity often couples to other electronic orders in a cooperative or competing fashion. Identifying external stimuli that tune between these two limits is of fundamental interest. Here, we show that strain perpendicular to the copper-oxide planes couples directly to the competing interaction between charge stripe order and superconductivity in La1.88Sr0.12CuO4 (LSCO). Compressive c-axis pressure amplifies stripe order within the superconducting state, while having no impact on the normal state. By contrast, strain dramatically diminishes the magnetic field enhancement of stripe order in the superconducting state. These results suggest that c-axis strain acts as tuning parameter of the competing interaction between charge stripe order and superconductivity. This interpretation implies a uniaxial pressure-induced ground state in which the competition between charge order and superconductivity is reduced. Tuning superconductivity and its interplay with other phases in cuprates yields insights into the underlying physics of this material class. Here, the authors performed a hard x-ray diffraction experiment on La1.88Sr0.12CuO4 showing that uniaxial pressure along the c-axis acts as a direct tuning parameter of the competition between superconductivity and charge order. [ABSTRACT FROM AUTHOR]

2D dilute magnetic semiconductors have been recently reported in transition metal dichalcogenides doped with spin‐polarized transition metal atoms, for example vanadium‐doped WS2 monolayers, which exhibit room‐temperature ferromagnetic ordering. However, a broadband characterization of the electronic band structure of these doped WS2 monolayers and its dependence on vanadium concentration is still lacking. Therefore, power‐dependent photoluminescence, resonant four‐wave mixing, and differential reflectance spectroscopies are performed here to study optical transitions close to the A exciton energy of vanadium‐doped WS2 monolayers at three different doping levels. Instead of a single A exciton peak, vanadium‐doped samples exhibit two photoluminescence peaks associated with transitions from a donor‐like level and the conduction band minima. Moreover, resonant Raman and second‐harmonic generation experiments reveal a blueshift in the B exciton energy but no energy change in the C exciton after vanadium doping. Density functional theory calculations show that the band structure is sensitive to the Hubbard U correction for vanadium, and several scenarios are proposed to explain the two photoluminescence peaks around the A exciton energy region. This work provides the first broadband optical characterization of these 2D dilute magnetic semiconductors, shedding light on the novel and tunable electronic features of V‐doped WS2 monolayers. [ABSTRACT FROM AUTHOR]

We calculate electronic structure and spin susceptibility dependencies on doping within the framework of a cluster perturbation theory for strongly correlated electronic systems. The change in the susceptibility with increasing doping is qualitatively consistent with the experimental data on resonant inelastic X-ray scattering and inelastic neutron scattering, as well as with the results of the calculations within the quantum Monte Carlo method. [ABSTRACT FROM AUTHOR]

The grazing X-ray diffraction study of phase-II NbS3 whiskers with charge density waves has shown that they exhibit pairs of broadened reflections from two close phases with the monoclinic angles β1 and β2 instead of single peaks. The phase with the smaller monoclinic angle β1 = 95.9°–97.2° is close in lattice parameters to phase I without charge density waves. Phase II with β2 = 99.9°–100.0° has a reduced b lattice parameter along the strongest bond, which implies an increased concentration of sulfur vacancies in this phase compared to phase I. It has been concluded that the studied whiskers have underwent a spinodal decomposition with the redistribution of sulfur vacancies resulting in the alternation of phases in the (001) direction perpendicular to the layers. A satellite structure indicating the formation of a superlattice with a period of 35.2 nm in this direction is observed in the most structurally perfect whisker of phase II. The spinodal decomposition is combined with high internal stresses present in whiskers with a monoclinic lattice. The partial spinodal decomposition is also observed in some phase-I whiskers without charge density waves with the appearance of thin layers of phase IV and phase II with the monoclinic angle β = 104°. The existence of thin layers of phase II in the bulk of phase I in such samples exposed to a high-frequency voltage has been confirmed by the presence of Shapiro steps on current–voltage characteristics. Spinodal decomposition should be taken into account to describe the properties of NbS3 whiskers nominally belonging to a certain polytype. [ABSTRACT FROM AUTHOR]

It is shown that many anomalies observed in underdoped cuprates, including anomalous spectral weight transfer and a large pseudogap, appear to have a common nature due to both the cluster structure of the underdoped phase and the specific mechanism of superconducting pairing. The combined action of these factors leads to the fact that at a temperature T lying in a certain temperature range Tc < T < T*, the crystal contains small isolated clusters that can exist both in superconducting and normal states, randomly switching between them. In this case, below Tc with a very high probability, the cluster is in a superconducting state, and above T*, it is in a normal state, and the interval Tc < T < T* is the region of existence of the so-called pseudogap phase. The temperatures Tc and T* for YBa2Cu3O6+δ were calculated depending on the doping level δ. The calculation results are in good agreement with the experiment without the use of fitting parameters. At a given T in the same temperature range, the time sequence of randomly arising superfluid density pulses from each cluster can be represented as a random process. The effective width Δωeff of the spectrum of such a random process will be determined by a correlation time, i.e., the characteristic time between successive on/off superconductivity in two different clusters. This time, according to the estimate, is ~ 10−15 s, which corresponds to Δωeff ~ 1 eV and explains the effect of spectral weight transfer to the high-frequency region. This approach also makes it possible to explain other anomalies observed in the vicinity of Tc: the reversibility of magnetization curves in a certain temperature range below Tc, the anomalous Nernst effect, and anomalous diamagnetism above Tc. [ABSTRACT FROM AUTHOR]

Strongly correlated materials respond sensitively to external perturbations such as strain, pressure, and doping. In the recently discovered superconducting infinite-layer nickelates, the superconducting transition temperature can be enhanced via only ~ 1% compressive strain-tuning with the root of such enhancement still being elusive. Using resonant inelastic x-ray scattering (RIXS), we investigate the magnetic excitations in infinite-layer PrNiO2 thin films grown on two different substrates, namely SrTiO3 (STO) and (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT) enforcing different strain on the nickelates films. The magnon bandwidth of PrNiO2 shows only marginal response to strain-tuning, in sharp contrast to the enhancement of the superconducting transition temperature Tc in the doped superconducting samples. These results suggest the bandwidth of spin excitations of the parent compounds is similar under strain while Tc in the doped ones is not, and thus provide important empirics for the understanding of superconductivity in infinite-layer nickelates. Nickelates have been shown to host unconventional superconductivity, and recently it has been found that the choice of substrate can significantly change the superconducting critical temperature. This suggests, that like some Cuprates, strain could be important. Here Gao, Fan, Wang, and coauthors find that magnetic excitations in a parent Nickelate are insensitive to substrate choice, and therefore strain, which differs markedly from the case of Cuprates. [ABSTRACT FROM AUTHOR]

Recent developments in 2D magnetic materials have motivated the search for new van der Waals magnetic materials, especially Ising‐type magnets with strong magnetic anisotropy. Fe‐based MPX3 (M = transition metal, X = chalcogen) compounds such as FePS3 and FePSe3 both exhibit an Ising‐type magnetic order, but FePSe3 receives much less attention compared to FePS3. This work focuses on establishing the strategy to engineer magnetic anisotropy and exchange interactions in this less‐explored compound. Through chalcogen and metal substitutions, the magnetic anisotropy is found to be immune against S substitution for Se whereas tunable only with heavy Mn substitution for Fe. In particular, Mn substitution leads to a continuous rotation of magnetic moments from the out‐of‐plane direction toward the in‐plane. Furthermore, the magnetic ordering temperature displays non‐monotonic doping dependence for both chalcogen and metal substitutions but due to different mechanisms. These findings provide deeper insight into the Ising‐type magnetism in this important van der Waals material, shedding light on the study of other Ising‐type magnetic systems as well as discovering novel 2D magnets for potential applications in spintronics. [ABSTRACT FROM AUTHOR]

Quantum fluctuations in low-dimensional systems and near quantum phase transitions have significant influences on material properties. Yet, it is difficult to experimentally gauge the strength and importance of quantum fluctuations. Here we provide a resonant inelastic x-ray scattering study of magnon excitations in Mott insulating cuprates. From the thin film of SrCuO2, single- and bi-magnon dispersions are derived. Using an effective Heisenberg Hamiltonian generated from the Hubbard model, we show that the single-magnon dispersion is only described satisfactorily when including significant quantum corrections stemming from magnon-magnon interactions. Comparative results on La2CuO4 indicate that quantum fluctuations are much stronger in SrCuO2 suggesting closer proximity to a magnetic quantum critical point. Monte Carlo calculations reveal that other magnetic orders may compete with the antiferromagnetic Néel order as the ground state. Our results indicate that SrCuO2—due to strong quantum fluctuations—is a unique starting point for the exploration of novel magnetic ground states. Magnetic excitations in infinite-layer cuprates have been intensively studied. Here the authors use resonant inelastic x-ray scattering and theoretical calculations to study magnons in thin films of SrCuO2, finding distinct magnon dispersion attributed to renormalization due to quantum fluctuations. [ABSTRACT FROM AUTHOR]

Electromagnetic waves propagating in a layered superconductor with arbitrary momentum, with respect to the main crystallographic directions, exhibit an unavoidable mixing between longitudinal and transverse degrees of freedom. Here we show that this basic physical mechanism explains the emergence of a well-defined absorption peak in the in-plane optical conductivity when light propagates at small tilting angles relative to the stacking direction in layered cuprates. More specifically, we show that this peak, often interpreted as a spurious leakage of the c-axis Josephson plasmon, is instead a signature of the true longitudinal plasma mode occurring at larger momenta. By combining a classical approach based on Maxwell's equations with a full quantum derivation of the plasma modes based on modeling the superconducting phase degrees of freedom, we provide an analytical expression for the absorption peak as a function of the tilting angle and light polarization. We suggest that an all-optical measurement in tilted geometry can be used as an alternative way to access plasma-wave dispersion, usually measured by means of large-momenta scattering techniques like resonant inelastic X-ray scattering (RIXS) or electron energy loss spectroscopy (EELS). [ABSTRACT FROM AUTHOR]

The mechanism of high-temperature superconductivity in copper oxides (cuprate) remains elusive, with the pseudogap phase considered a potential factor. Recent attention has focused on a long-range symmetry-broken charge-density wave (CDW) order in the underdoped regime, induced by strong magnetic fields. Here by 63,65Cu-nuclear magnetic resonance, we report the discovery of a long-range CDW order in the optimally doped Bi2Sr2−xLaxCuO6 superconductor, induced by in-plane strain exceeding ∣ε∣ = 0.15 %, which deliberately breaks the crystal symmetry of the CuO2 plane. We find that compressive/tensile strains reduce superconductivity but enhance CDW, leaving superconductivity to coexist with CDW. The findings show that a long-range CDW order is an underlying hidden order in the pseudogap state, not limited to the underdoped regime, becoming apparent under strain. Our result sheds light on the intertwining of various orders in the cuprates. The authors study the optimally-doped cuprate superconductor Bi2Sr2−xLaxCuO6 by nuclear magnetic resonance. They find a long-range charge density wave (CDW) order induced by uniaxial strain, showing that CDW order is a hidden order of the pseudogap state, not limited to the underdoped regime. [ABSTRACT FROM AUTHOR]

The microscopic mechanism for the disappearance of superconductivity in overdoped cuprates is still under heated debate. Here we use scanning tunneling spectroscopy to investigate the evolution of quasiparticle interference phenomenon in Bi2Sr2CuO6+δ over a wide range of hole densities. We find that when the system enters the overdoped regime, a peculiar quasiparticle interference wavevector with arc-like pattern starts to emerge even at zero bias, and its intensity grows with increasing doping level. Its energy dispersion is incompatible with the octet model for d-wave superconductivity, but is highly consistent with the scattering interference of gapless normal carriers. The gapless quasiparticles are mainly located near the antinodes and are independent of temperature, consistent with the disorder scattering mechanism. We propose that a branch of normal fluid emerges from the pair-breaking scattering between flat antinodal bands in the quantum ground state, which is the primary cause for the reduction of superfluid density and suppression of superconductivity in overdoped cuprates. The authors use scanning tunneling spectroscopy to investigate the evolution of quasiparticle interference in a single-layer cuprate compound. They find evidence for an emergent normal fluid in the superconducting ground state of overdoped samples, with the gapless quasiparticles located at the antinodal region of reciprocal space. [ABSTRACT FROM AUTHOR]

Vortices in superconductors can help identify emergent phenomena but certain fundamental aspects of vortices, such as their entropy, remain poorly understood. Here, we study the vortex entropy in underdoped Bi2Sr2CaCu2O8+x by measuring both magneto-resistivity and Nernst effect on ultrathin flakes (≤2 unit-cell). We extract the London penetration depth from the magneto-transport measurements on samples with different doping levels. It reveals that the superfluid phase stiffness ρs scales linearly with the superconducting transition temperature Tc, down to the extremely underdoped case. On the same batch of ultrathin flakes, we measure the Nernst effect via on-chip thermometry. Together, we obtain the vortex entropy and find that it decays exponentially with Tc or ρs. We further analyze the Nernst signal above Tc in the framework of Gaussian superconducting fluctuations. The combination of electrical and thermoelectric measurements in the two-dimensional limit provides fresh insight into high temperature superconductivity. The authors study the vortex entropy in ultrathin flakes of the underdoped cuprate superconductor Bi2Sr2CaCu2O8+x by measuring both magneto-resistivity and Nernst effect. They find that, while the superfluid phase stiffness varies linearly with Tc, the vortex entropy decreases exponentially at lower Tc. [ABSTRACT FROM AUTHOR]

Understanding the interplay between charge, nematic, and structural ordering tendencies in cuprate superconductors is critical to unraveling their complex phase diagram. Using pump-probe time-resolved resonant X-ray scattering on the (0 0 1) Bragg peak at the Cu L3 and O K resonances, we investigate nonequilibrium dynamics of Qa = Qb = 0 nematic order and its association with both charge density wave (CDW) order and lattice dynamics in La1.65Eu0.2Sr0.15CuO4. The orbital selectivity of the resonant X-ray scattering cross-section allows nematicity dynamics associated with the planar O 2p and Cu 3d states to be distinguished from the response of anisotropic lattice distortions. A direct time-domain comparison of CDW translational symmetry breaking and nematic rotational-symmetry breaking reveals that these broken symmetries remain closely linked in the photoexcited state, consistent with the stability of CDW topological defects in the investigated pump fluence regime. [ABSTRACT FROM AUTHOR]

The rigorous formulations of boson (the ideal Bose gas) and fermion-pair Bose–Einstein (BE) condensations reveal that the two condensed states are different; the boson condensation given by the boson coherent state is a sound condensed state based on a large number of states corresponding to the grand canonical ensemble of the classical ideal gas (average particle number N) where the norm of the coherent state is equivalent to the grand (canonical) partition function Ξ 0 = e N of the latter. The fermion-pair condensation is a very limited condensed state formed between holes and fermion-pairs and its condensate is a fermion-pair and hole condensate. The singlet-bond (SB) superconductivity theory for cuprate high-temperature superconductors finds the following; (1) the superconducting transition is a first-order transition, (2) the experimentally observed exponential behavior of the specific heat coefficient γ (T) ≡ C (T) / T near T c is caused by the high energy excitations of superconducting SB-pairs to the normal-state insulating immobile SB-pairs beyond the characteristic energy scale ∼ k B T c of the condensation energy, which is the same origin as that of the exponential γ (T) behavior in the BCS superconductivity, and (3) Josephson tunneling in d-wave superconductor Josephson junction cannot give rise to the so-called π -shift Josephson phase in both the underdoped and overdoped cuprate superconductor Josephson junctions. [ABSTRACT FROM AUTHOR]

Understanding the interplay between charge, nematic, and structural ordering tendencies in cuprate superconductors is critical to unraveling their complex phase diagram. Using pump-probe time-resolved resonant X-ray scattering on the (0 0 1) Bragg peak at the Cu L3 and O K resonances, we investigate nonequilibrium dynamics of Qa = Qb = 0 nematic order and its association with both charge density wave (CDW) order and lattice dynamics in La1.65Eu0.2Sr0.15CuO4. The orbital selectivity of the resonant X-ray scattering cross-section allows nematicity dynamics associated with the planar O 2p and Cu 3d states to be distinguished from the response of anisotropic lattice distortions. A direct time-domain comparison of CDW translational symmetry breaking and nematic rotational-symmetry breaking reveals that these broken symmetries remain closely linked in the photoexcited state, consistent with the stability of CDW topological defects in the investigated pump fluence regime. [ABSTRACT FROM AUTHOR]

The document titled "Alex's Vision in Functional Quantum Matter" is a personal reflection on the life and work of Karl Alex Müller, a renowned scientist and co-discoverer of high-Tc superconductors. The author, Davor Pavuna, shares his experiences and interactions with Müller, highlighting Müller's visionary approach to obtaining desired functionality in complex quantum matter. The document also mentions the importance of well-characterized samples in research and the role of pseudogap in high-Tc oxides. Overall, the document provides insights into Müller's contributions to the field of condensed matter physics and his lasting legacy. [Extracted from the article]

The given text provides a collection of personal anecdotes and experiences with K. Alex Müller, a Nobel Prize-winning physicist known for his work on high-temperature superconductivity. The authors share their memories of collaborating with Müller, discussing their scientific endeavors and the impact he had as a mentor. The text also explores Müller's wide-ranging interests outside of physics, including his passion for cars and his knowledge in various fields. Overall, the text offers a glimpse into Müller's life and provides insights into his personality and contributions to the scientific community. [Extracted from the article]