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We have investigated temporal fluctuation of superconducting qubits via the time-resolved measurement for an IBM Quantum system. We found that the qubit error rate abruptly changes during specific time intervals. Each high error state persists for several tens of seconds and exhibits an on-off behavior. The observed temporal instability can be attributed to qubit transitions induced by a measurement stimulus. Resonant transition between fluctuating dressed states of the qubits coupled with high-frequency resonators can be responsible for the error-rate change. [ABSTRACT FROM AUTHOR]

In our article, we show the n value determined from measurements using the magnetic field sweep method (curves of E from B/Bc) and the current sweep method (curves of E from I/Ic). The results from these two methods allowed for a scientific n value analysis. Moreover, measurements using these two methods allow for a better understanding of the behavior of superconducting wires after the transition from the superconducting state to the normal (resistive) state. Measurements were made for the NbTi wire at 4.2 K, MgB2 at the temperature range from 4.2 to 30 K, and high-temperature superconducting tape at 77 K. The magnetic field sweep method results show that the n value has a constant value independent of an increase in the magnetic field, number of filaments, type of boron, diameter of the wire, and small amount of the dopant. Moreover, research studies point out that the n value in the magnetic field sweep method depends on the type of superconductor material, a large amount of doping at high temperatures, and the low density of pinning centers. Based on the results obtained, it can be indicated that each superconducting material will have a constant n value. Measurements carried out using the current sweep method showed that the n value decreases significantly with an increase in the magnetic field. Moreover, research studies have shown that the n value depends on the number of filaments, type of boron, dopant, wire diameter, and temperature. On this basis, it can be indicated that the n value for the current sweep method depends on the morphology and structure of the superconducting wires. In addition, based on the samples measured in this research, the current sweep method allows for higher n values than the magnetic field sweep method in low magnetic fields. However, the magnetic field sweep method allows obtaining higher n values than the current sweep method in middle and high magnetic fields. [ABSTRACT FROM AUTHOR]

Recent studies have shown that proximity effects are able to substantially modulate the superconducting properties of various quasi-two-dimensional layered materials such as FeSe, FeSeTe, NbSe2, and NbS2. Due to their high surface charge concentration and high dielectric constants, ferroelectric materials provide an interesting avenue for inducing proximity effects in layered superconductors. In this study, we explore the interactions between FeSeTe and the two-dimensional ferroelectrics CuInP2S6 and CuInP2Se6. We found that contrary to the normal behavior of FeSeTe, FeSeTe/CuInP2S6, and FeSeTe/CuInP2Se6 heterostructures display a peculiar two-step superconducting transition. Further testing revealed a hysteresis loop in the IV curves of these samples when measured below the critical temperature indicating the presence of disorder and domains within FeSeTe. We conclude that these domains are responsible for the two-step transition in FeSeTe and hypothesize that they are induced by the domain structure of the aforementioned ferroelectric materials. [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]

A novel material is obtained by modifying pristine YBCO superconductor via simultaneous partial substitution of Sr for Ba and Se for O. The intended stoichiometry was YBa2−xSrxCu3O7−xSex with x=0.5, 0.75 and 1; and x≈1 yielded the most interesting results considered in detail. We confirmed that Se atoms indeed enter the superconductor lattice cell. The obtained polycrystalline material contains five phases, with the major phase (>44wt.%) being YBa1.4Sr0.6Cu3O6Se0.5. The synthesized superconductor demonstrates unique properties, including (i) two superconducting transitions with Tc1≈36K and Tc2≈13K yielding the Wohlleben effect; (ii) strong-coupling d-wave superconductivity (with 2Δ∕(kBTc)≈ 5); (iii) Schottky anomaly in the heat capacity; and, most importantly, (iv) a very unusual anomaly in the heat capacity which can be associated with the quantum criticality typically observable at much higher fields. The fact that the quantum criticality is visible in weaker fields (∼7T) may open opportunities for exploration of the interplay between superconductivity and pair density waves by wide research community particularly when its pure phase is available. To facilitate this, the stability of single-phase YBa1.4Sr0.6Cu3O6Se0.5 is analyzed using machine learning methods. [ABSTRACT FROM AUTHOR]

This study investigates hollow single‐crystal top‐seeded melt growth (TSMG) YBa2Cu3O7−x (YBCO or Y123) samples welded with Ag‐added TSMG YBCO solder materials produced using NdBCO/YBCO/MgO thin‐film seeds. Three main samples and one solder material are produced by the TSMG method. In order to increase the dimensions of the bulk YBCO superconductor, two slices of the solder material and the main samples are stacked on top of each other with the c‐axis parallel and welded at 1030 °C. X‐ray diffraction patterns, polarized optical photographs, and SEM micrographs are taken to determine the structural properties of the samples. A preferential orientation in the c‐axis is observed with a good connection. Low‐temperature resistance and magnetization measurements are made for the specimens taken from the welding region. A sharp superconducting transition occurs at 0 T around 93 K for welding regions of W‐ab and W‐bc specimens. The critical current densities (Jc) are high as in the main samples. At the same time, the Jc values at 77 K and 0 T are found as 1.54 × 104, 1.98 × 104, 2.21 × 104, 2.31 × 104, and 2.36 × 104 A cm−2 for the W‐a, W‐ab, W‐b, W‐bc, and W‐c specimens, respectively. The single‐grain feature is not impaired; thus, the absence of additional grain boundaries facilitates the current passage. [ABSTRACT FROM AUTHOR]

The vortex phase diagram and superconducting properties of air‐annealed FeTe0.8S0.2 single crystals are investigated. The annealed samples exhibit a superconducting transition, as confirmed by temperature‐dependent resistivity measurements. The thermally activated energy is calculated from the magnetotransport measurements, and the analysis shows that as the magnetic field increases, there is a crossover from single to collective vortex pinning. The vortex phase diagrams have been determined by analyzing magnetic field‐dependent resistivity, revealing the transitions from an unpinned vortex liquid region to a pinned vortex liquid state and further transition from this pinned state to a vortex glass state. Temperature‐dependent magnetization measurement determines the superconducting volume fraction. The critical current densities, as a function of the magnetic field (JC(H)), have been estimated from the magnetization versus magnetic field loops measured at various temperatures. Bean's critical state model estimates the JC values, and for an optimized annealed crystal, the self‐field JC at 2 K is ≈4.6×104 A cm−2$\approx 4.6 \times \left(10\right)^{4} \left(\text{ A cm}\right)^{- 2}$. The normalized pinning force density in the samples is determined using the Dew Hughes model to identify the pinning mechanisms. The temperature‐dependent JC data analysis indicates the presence of δl$\delta l$‐pinning in the samples. Theoretical models analyze experimental observations to understand the vortex pinning mechanisms. [ABSTRACT FROM AUTHOR]

The effect of medium fluences (from 1019 е/cm2 to 1020 е/cm2) of fast electron irradiation or the change in the praseodymium concentration in the range 0.0 ≤ z ≤ 0.5 on the excess conductivity of optimally oxygen-doped YBa2Cu3O7–δ single crystals has been investigated. Irradiation leads to the appearance of a significant number of defects that cause a decrease in anisotropy, an appreciable increase in phonon scattering, reduction of Tc, and broadening of the superconducting transition. Under the conditions specified, the temperature dependence of electrical resistivity is approximated with high accuracy by the charge carriers' scattering on defects and phonons, and fluctuating conductivity in the Lawrence–Doniach model. It was determined that at fluences 0 ≤ Ф ≤ 6.5⋅1019 е/cm2, the value of the transverse coherence length ξс(0) increases with an increase of Ф by about three times or more than four times as the content of praseodymium in the sample increases to z ≈ 0.42. In both cases, the 2D–3D crossover point shifts upward in temperature. In contrast to the case of irradiation with low fluences (Ф ≤ 1019 е/cm2) or doping with praseodymium up to concentrations z ≤ 0.39, irradiation with medium fluences and doping with praseodymium at higher concentrations leads to a nonmonotonic dependence of the transverse coherence length ξс(0) on the irradiation fluence, with characteristic maxima at Ф ∼ (7–8)⋅1019 е/cm2 or z ≈ 0.42, which may be due to the general suppression of the superconducting characteristics. [ABSTRACT FROM AUTHOR]

We present dynamical equations that are valid in the vicinity of a phase transition to the superconducting state. In writing the equations, we take the possible influence of the magnetic interaction between charge carriers and temperature fluctuations into account. We discuss the type of the phase transition under study. We argue in favor of the applicability of stochastic dynamical model A according to the standard classification (the stochastic model with one two-component field without a conservation law) to describe the dynamics of this phase transition. [ABSTRACT FROM AUTHOR]

Based on the characteristic change in the resistance of superconducting devices during the superconducting transition, a quantitative method to determine the temperature of superconducting devices has been proposed. This method can detect in real time whether the temperature of the superconducting device exceeds the superconducting transition temperature, thereby enabling quick reduction of the trapped magnetic flux in devices. We apply this method in our experiment, which uses a superconducting 22 subarrays programmable Josephson voltage standard device and obtains satisfactory results. We conclude that this method can efficiently reduce the trapped magnetic flux in superconducting devices and facilitate testing for measurement systems which do not possess thermometers. [ABSTRACT FROM AUTHOR]

The possibility of the existence of the photovoltaic Hall effect, i.e., the transverse response of a two-dimensional system with a constant driving electric field acting in the plane of the system, to circularly polarized incident radiation near the phase transition of the system to the superconducting state from the normal phase at T > Tc is discussed. It is shown that the photovoltaic Hall effect can be caused by superconducting fluctuations in the regime where normal electrons do not contribute to this effect. [ABSTRACT FROM AUTHOR]

This article reports the successful synthesis of single crystalline two-dimensional thin flakes of NbSe2. The XRD (X-ray diffraction) pattern of the grown crystal ensured its crystallization in a single phase with a hexagonal structure. The EDAX (energy dispersive X-ray analysis) endorsed the stoichiometry of the as-grown sample. To study the vibrational modes, the Raman spectra were recorded, which exhibited the expected four Raman active modes. The resistance vs temperature measurement showed a well-established superconducting transition (Tc) at 7.3 K. The ZFC (zero-field cooled) and FC (field cooled) magnetization curves, as well as the isothermal M−H (magnetization vs field) measurements, have been performed for both in-plane and out-of-plane H directions. Distinct anisotropy is observed in both magnetization and magneto-transport measurements with field direction, leading to different critical fields (Hc). Out-of-plane magneto-transport data hints towards the existence of a filamentary state. The density functional theory (DFT) has been used to study the band structure of NbSe2. Although the bulk band structure confirmed metallic behavior, the same of mono-layers of NbSe2 within the GGA+U framework showed a band gap of 1.17 eV. The article addresses the anisotropy in the electronic and magneto-transport of 2D superconductor NbSe2. [ABSTRACT FROM AUTHOR]

This article reports the successful synthesis of single crystalline two-dimensional thin flakes of NbSe2. The XRD (X-ray diffraction) pattern of the grown crystal ensured its crystallization in a single phase with a hexagonal structure. The EDAX (energy dispersive X-ray analysis) endorsed the stoichiometry of the as-grown sample. To study the vibrational modes, the Raman spectra were recorded, which exhibited the expected four Raman active modes. The resistance vs temperature measurement showed a well-established superconducting transition (Tc) at 7.3 K. The ZFC (zero-field cooled) and FC (field cooled) magnetization curves, as well as the isothermal M−H (magnetization vs field) measurements, have been performed for both in-plane and out-of-plane H directions. Distinct anisotropy is observed in both magnetization and magneto-transport measurements with field direction, leading to different critical fields (Hc). Out-of-plane magneto-transport data hints towards the existence of a filamentary state. The density functional theory (DFT) has been used to study the band structure of NbSe2. Although the bulk band structure confirmed metallic behavior, the same of mono-layers of NbSe2 within the GGA+U framework showed a band gap of 1.17 eV. The article addresses the anisotropy in the electronic and magneto-transport of 2D superconductor NbSe2. [ABSTRACT FROM AUTHOR]

Analytical instruments or scientific instruments are indispensable for scientific research and industry. The analytical instruments require a detector that converts physical quantities to be measured (measurands) to electric signals. This Tutorial describes the basics of quantum and thermal detectors, the operation principles of superconductor detectors, and the ultimate performance of state-of-art analytical instruments with superconductivity. We still face fundamental issues, such as the classical Fano factor, the relation between energy gap and mean carrier creation energy, quasiparticle dynamics, and the intermediate state in the middle of superconducting transition; and engineering issues, such as the small sensitive area and the spatially nonuniform response. Nevertheless, enormous efforts have matured superconductor detectors, which enables us to solve the inherent problems of conventional analytical instruments. As an example of the analytical results, we describe x-ray spectroscopy and mass spectrometry at our institute by using three detector types: superconductor tunnel junction, transition edge sensor, and superconductor strip. Microwave kinetic inductance and metallic magnetic calorimetric types are also described. The analytical results may contribute to a wide range of fields, such as dentistry, molecular biology, energy-saving society, planetary science, and prebiotic organic molecules in space. [ABSTRACT FROM AUTHOR]

In this article, we report on the basic physical properties of a polycrystalline Nb 5 Si 2 B sample, presenting and discussing experimental results of the temperature and field-dependent magnetization M(T, μ 0 H), heat capacity C p (T), electrical resistivity ρ (T), thermoelectric power S(T), and thermal conductivity κ (T) measurements. We also refer to the crystal structure properties of the obtained phase, but primarily we focus on determining the superconducting properties, because based on above experimental data, we deduce on the second-type bulk superconducting transition at T c ≃ 8.2 K. A set of characteristic superconducting state parameters was estimated. Interestingly, although T c gradually and regularly decreases with increasing magnetic field strength, scaling the temperature dependence of the upper critical field μ 0 H c 2 using the Werthamer–Helfand–Hohenberg (WHH) or Ginzburg–Landau (GL) theories does not reflect well on both models. The dimensionless specific heat jump at Δ C p / γ n T c attains ∼ 0.3 , which is significantly smaller than the classical BCS value of Δ C p / γ n T c = 1.43. In addition, the electronic specific heat C e l below T c does not reproduce the isotropic single-gap BCS behavior. Accordingly, these results indicate that Nb 5 Si 2 B is an unconventional BCS superconductor with an anisotropic or multi-valued gap. At T = 300 K, S(T) reaches a negative value of − 5.8 μ V/K and vanishes almost linearly with diminishing temperature, as expected for ordinary metals. On the other hand, from κ (T) data, it turns out that the lattice thermal conductivity dominates over the electronic contribution up to room temperature. [ABSTRACT FROM AUTHOR]

Kinetic inductances of superconducting nanostrips with a meander pattern are theoretically investigated based on the London model, and the effect of the current crowding at the turns of the nanostrips is considered. The complex current approach is developed for analytical investigation of the kinetic inductance of nanostrips with turns for thin d < λ and narrow w ≪ λ 2 / d superconducting strips, where d is the strip thickness, w is the strip width, and λ is the London penetration depth. We show that the current distribution in superconducting nanostrips of w d ≪ λ 2 is identical to that in normal conducting nanostrips of w d ≪ δ 2 / 2 , where δ is the skin depth, and the dependence of the kinetic inductance on the nanostrip geometry is identical to that of the normal resistance. Effects of the edge defects of superconducting strips upon the kinetic inductance are also considered. [ABSTRACT FROM AUTHOR]

High-quality superconductor/topological material heterostructures are highly desired for realisation of topological superconductivity and Majorana physics. Here, we demonstrate a method to directly draw nanoscale superconducting β-Sn patterns in the plane of a topological Dirac semimetal (TDS) α-Sn thin film by irradiating a focused ion beam and taking advantage of the heat-driven phase transition of α-Sn into superconducting β-Sn. The β-Sn nanowires embedded in a TDS α-Sn thin film exhibit a large superconducting diode effect (SDE), whose rectification ratio η reaches a maximum of 35% when the magnetic field is applied parallel to the current. The results suggest that the SDE may occur at the α-Sn/β-Sn interfaces where the TDS α-Sn becomes superconducting by a proximity effect. Our work thus provides a universal platform for investigating quantum physics and devices based on topological superconducting circuits of any shape. Topological superconductivity may have important implications for fault-tolerant quantum computing, but its practical implementation remains challenging. Here, the authors report the fabrication of nanoscale heterojunctions based on superconducting β-Sn and topological Dirac semimetal α-Sn, showing superconducting diode rectification ratios up to 35%. [ABSTRACT FROM AUTHOR]

The moiré superconductor magic-angle twisted bilayer graphene (MATBG) shows exceptional properties, with an electron (hole) ensemble of only ~1011 carriers per square centimeter, which is five orders of magnitude lower than traditional superconductors (SCs). This results in an ultralow electronic heat capacity and a large kinetic inductance of this truly two-dimensional SC, providing record-breaking parameters for quantum sensing applications, specifically thermal sensing and single-photon detection. To fully exploit these unique superconducting properties for quantum sensing, here, we demonstrate a proof-of-principle experiment to detect single near-infrared photons by voltage biasing an MATBG device near its superconducting phase transition. We observe complete destruction of the SC state upon absorption of a single infrared photon even in a 16-square micrometer device, showcasing exceptional sensitivity. Our work offers insights into the MATBG-photon interaction and demonstrates pathways to use moiré superconductors as an exciting platform for revolutionary quantum devices and sensors. [ABSTRACT FROM AUTHOR]

2D materials provide an ideal platform to explore novel superconducting behavior including Ising superconductivity, topological superconductivity and Majorana bound states in different 2D stoichiometric Ta‐, Nb‐, and Fe‐based crystals. However, tuning the element content in 2D compounds for regulating their superconductivity has not been realized. In this work, the synthesis of high quality Fe1+yTe with tunable Fe content by chemical vapor deposition (CVD) is reported. The quality and composition of Fe1+yTe are characterized by Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). The superconducting behavior of Fe1+yTe crystals with varying Fe contents is observed. The superconducting transition of selected Fe1.13±0.06Te sample is sharp (ΔTc = 1 K), while Fe1.43±0.07Te with a high‐Fe content shows a relative broad superconducting transition (ΔTc = 2.6 K) at zero magnetic field. Significantly, the conspicuous vortex flow and a transition from a 3D vortex liquid state to a 2D vortex liquid state is observed in Fe1.43±0.07Te sample. This work highlights the tunability of the superconducting properties of Fe1+yTe and sheds light on the vortex dynamics in Fe‐based superconductors, which facilitates them to understand the intrinsic mechanisms of high‐temperature superconductivity. [ABSTRACT FROM AUTHOR]

Many modern accelerators rely on superconducting radio-frequency (SRF) cavities to accelerate particles. When these cavities are cooled to the superconducting state, a fraction of the ambient magnetic field (e.g., Earth's magnetic field) may be trapped in the superconductor. This trapped flux can significantly increase the power dissipation of the SRF cavities. It is, therefore, crucial to understand the underlying mechanism of how magnetic flux is trapped and what treatments and operating conditions can reduce the flux-trapping efficiency. A new experiment was designed that enables a systemic investigation of flux trapping. It allows for independent control of cooldown conditions, which might have an influence on flux trapping: temperature gradient across the superconductor during cooldown, cooldown rate, and ambient magnetic field. For exhaustive studies, the setup was designed for quick thermal cycling, permitting up to 300 superconducting transitions in one day. In this paper, the setup and operation is described in detail and an estimation of the measurement errors is given. Exemplary data are presented to illustrate the efficacy of the system. [ABSTRACT FROM AUTHOR]

We report a synthesis of two members of recently discovered high-temperature superconductors of the 12442 family, with formula MCa2Fe4As4F2 (M = Rb, K) and transition temperatures of 32.7 and 34.6 K, respectively. Quality of the samples was assessed using X-ray powder diffraction, superconducting transitions were identified through transport and magnetic experiments. The temperature dependence of the upper critical field and vortex activation energy was investigated under magnetic fields up to 19 T. Two distinct thermally activated flux flow regimes were observed in both systems. Field dependences of activation energy indicate a change in the properties of vortex matter in these regimes and distinctly different dissipation mechanisms, reminiscent of cuprate HTSC. [ABSTRACT FROM AUTHOR]

FeTe monolayer islands situated on a topological insulator Bi2Te3 (0001) surface were recently reported to exhibit the opening of an energy gap below temperatures T ~ 6 K, which could be due to a superconducting phase transition. In this work, we present a magnetic field dependent transport study proving that this gap is indeed of superconducting origin. Upon cooling, several drops in resistance are observed in the temperature range between 6 K and 2 K, indicating multiple transitions. Using the Ginzburg-Landau theory, we show that the critical magnetic field of the dominant high-temperature transition at ~ 6 K is governed by orbital Cooper pair breaking in larger FeTe islands, large enough to exceed the superconductive coherence length ξ . At smaller island sizes, transitions at lower temperatures < 6 K become more prominent, showing significantly increased critical fields dominated by paramagnetic pair breaking. The multiphase superconducting behaviour is in line with an observed wide distribution of FeTe islands width 5–100 nm and seems to reflect disorder effects at the interface to Bi2Te3. The proof of local superconductivity makes the FeTe interface to the topological insulator Bi2Te3 substrate a potential host of topological superconductivity. [ABSTRACT FROM AUTHOR]

Exploring superconducting materials stands as a pivotal pursuit in condensed matter physics, particularly, the investigation of superconductivity in two-dimensional metal hydrides is of paramount importance due to its intriguing nature. Our study focuses on elucidating the metallic state of van der Waals layered TM-H (TM = Ti, Zr, Hf) compounds, a key factor in predicting their superconducting (SC) characteristics. Leveraging an evolutionary algorithm rooted in density functional theory, we predicted the structures of hydrides, including Ti 2 H 2 , Ti 2 H 4 , Zr 2 H 2 , Zr 2 H 4 , Zr 2 H 5 , Hf 2 H 2 , Hf 2 H 4 , Hf 2 H 5 , and determined their energetically stable structures. Along with exploring the potential for SC, we conducted a comprehensive examination of relevant electronic properties. A significant aspect addressed was the influence of anharmonic phonon properties in determining the stochastic self-consistent harmonic approximation. These findings underscore the pivotal role of anharmonicity in determining the SC of two-dimensional metal hydrides. [Display omitted] • A variety of atomic configurations of hydrogen are unveiled in the discovery of novel two-dimensional monolayers featuring transition metals. • Enhancing T c relies significantly on the impact of quantum fluctuations and anharmonic corrections. • The SSCHA method renormalizes an analytical expression for lattice dynamics, ensuring stabilization at finite temperatures. • Hf 2 H 5 exhibits superconductivity with a notable T c of 10.3 K. [ABSTRACT FROM AUTHOR]

Inter-granular Sn particles affect transport and magnetic properties both in the normal and superconducting states of polycrystalline GdBa2Cu3O7−δ (GdBCO) superconductors drastically. Normal state resistivity at 300 K increases ~ 18.0 times as the concentration of Sn is increased. An unusual upturn in resistivity as a function of temperature curve with a dip is observed in GdBCO with 3.0 wt% of Sn in which suppression of superconducting phase transition has been observed. Current-voltage (IV) curves below Tc exhibit nonlinear features in composites of GdBCO and Sn. Magnetization (M) as a function of magnetic field (H) curves at 2.0 –20.0 K in GdBCO shifts strongly with the addition of 1.0 wt% Sn. We have extracted irreversible magnetization, lower critical field (Hc1) and magnetic critical density (Jcm) as a function of H at several T. The maximum pinning force density is 0.4 GN/m3 in GdBCO which is reduced in the Sn added GdBCO. [ABSTRACT FROM AUTHOR]

The structural analogue of iron-based superconductors the BaMn2P2 and BaMn2As2 compounds under hydrostatic pressure upto 140 GPa were studied within the framework of DFT + U. The transition from an antiferromagnetic insulator to an antiferromagnetic metal is observed under pressure of 6.4 GPa for BaMn2P2 and 8.3 GPa for BaMn2As2. This second order phase transition to the AFM metallic state provides an appropriate normal state for possible superconductivity in these materials. Moreover, further increase in pressure leads to a series of first order magnetostructural phase transitions between different antiferromagnetic phases, then to a ferromagnetic metal and finally to a nonmagnetic metal. In case of doping, these compounds could potentially be superconductors under pressure (above 6–8 GPa) with critical temperature growing under pressure. [ABSTRACT FROM AUTHOR]

The structural analogue of iron-based superconductors the BaMn2P2 and BaMn2As2 compounds under hydrostatic pressure upto 140 GPa were studied within the framework of DFT + U. The transition from an antiferromagnetic insulator to an antiferromagnetic metal is observed under pressure of 6.4 GPa for BaMn2P2 and 8.3 GPa for BaMn2As2. This second order phase transition to the AFM metallic state provides an appropriate normal state for possible superconductivity in these materials. Moreover, further increase in pressure leads to a series of first order magnetostructural phase transitions between different antiferromagnetic phases, then to a ferromagnetic metal and finally to a nonmagnetic metal. In case of doping, these compounds could potentially be superconductors under pressure (above 6–8 GPa) with critical temperature growing under pressure. [ABSTRACT FROM AUTHOR]

Superconductivity of iron chalocogenides is strongly enhanced under applied pressure yet its underlying pairing mechanism remains elusive. Here, we present a quantum oscillations study up to 45 T in the high-Tc phase of tetragonal FeSe0.82S0.18 up to 22 kbar. Under applied pressure, the quasi-two-dimensional multi-band Fermi surface expands and the effective masses remain large, whereas the superconductivity displays a threefold enhancement. Comparing with chemical pressure tuning of FeSe1−xSx, the Fermi surface expands in a similar manner but the effective masses and Tc are suppressed. These differences may be attributed to the changes in the density of states influenced by the chalcogen height, which could promote stronger spin fluctuations pairing under pressure. Furthermore, our study also reveals unusual scattering and broadening of superconducting transitions in the high-pressure phase, indicating the presence of a complex pairing mechanism. [ABSTRACT FROM AUTHOR]

Superconductivity often emerges as a dome around a quantum critical point (QCP) where long-range order is suppressed to zero temperature, mostly in magnetically ordered materials. However, the emergence of superconductivity at charge-order QCPs remains shrouded in mystery, despite its relevance to high-temperature superconductors and other exotic phases of matter. Here, we present resistance measurements proving that a dome of superconductivity surrounds the putative charge-density-wave QCP in pristine samples of titanium diselenide tuned with hydrostatic pressure. In addition, our quantum oscillation measurements combined with electronic structure calculations show that superconductivity sets in precisely when large electron and hole pockets suddenly appear through an abrupt change of the Fermi surface topology, also known as a Lifshitz transition. Combined with the known repulsive interaction, this suggests that unconventional s± superconductivity is mediated by charge-density-wave fluctuations in titanium diselenide. These results highlight the importance of the electronic ground state and charge fluctuations in enabling unconventional superconductivity. [ABSTRACT FROM AUTHOR]

By using a superconducting transition edge sensor (TES) to measure the thermal energy of individual decay events with high energy resolution, decay energy spectrometry provides a unique fingerprint to identify each radionuclide in a sample. The proposed measurement requires optimizing the thermal parameters of the detector for use with 5 MeV scale energy deposited by alpha decay of the sample radionuclides. The thermal performance of deep-etched silicon TES chips is examined with the use of an onboard resistive heater. With known heater power and bath temperature, the thermal conductance, heat capacity, and frame temperature are calculated and compared to theory. [ABSTRACT FROM AUTHOR]

This study explores the superconducting characteristics of bulk MgB 2 samples fabricated through in-situ sintering, employing ultrasonically treated boron dispersed in a highly viscous 1-heptanol solution. Ultrasonication, performed at 75% power for 120 min, effectively reduces the average particle size of commercial boron to 172 nm. Post-ultrasonication analysis reveals a purified boron composition, yielding bulk MgB 2 with a predominant MgB 2 phase and minimal MgO impurities, as confirmed by X-ray diffraction (XRD). The XRD results further demonstrate consistent lattice parameters ' a ' and ' c ' at approximately 3.086 and 3.523 Å, respectively, ruling out carbon contamination. All samples exhibit a superconducting transition temperature (T c , onset) around 37.5 K, with a narrow superconducting transition width (Δ T c) of about 0.5 K. The critical current characteristics of the 120-min ultrasonicated boron incorporated into bulk MgB 2 reveal a significant enhancement in the self-field critical current density (J c), reaching 607 kA/cm2 at 10 K and 417 kA/cm2 at 20 K. This improvement, constituting a 10% advancement over previously reported boron produced in propenal media, is attributed to microstructural changes. Microscopic analysis highlights the integration of nanoscale MgB 2 grains, fostering improved grain boundary pinning, as supported by Dew-Hughes approximations. This leads to a more than twofold increase in J c compared to bulk MgB 2 materials derived from pure commercial boron sources. [ABSTRACT FROM AUTHOR]

The 2023 MRE HP Special Volume showcases the collaborative progress in high-pressure physics and chemistry, highlighting the emergence of unique compositions and physical properties in borides, nitrides, and hydrides due to pressure-induced crystal chemistry. The volume explores the superionic and electride states in materials, revealing new classes of superconducting pentaborides and polymeric nitrogen materials with high-energy-density properties. Additionally, the quest for room-temperature superconductivity in pressure-stabilized metal hydrides is discussed, along with the challenges and cautions associated with experimental characterization. Lastly, the volume delves into the innovative use of high-energy X-ray photon correlation spectroscopy and the discovery of a mountaintop impact crater in China, providing new insights into high-pressure minerals and impact crater formation. [Extracted from the article]

Recently, high-temperature superconductivity has been found at the interface between two Mott insulators, PrBa2Cu3O7 and La2CuO4. In this work, we demonstrate our tuning of this interface superconductor by ionic liquid gating. By varying gate voltage, VG, a superconductor–insulator phase transition was achieved. Hall-effect measurements suggest that the carrier density, which can be tuned continuously from 1.86 × 1014 to 3.78 × 1014 cm−2 for VG varying from −0.3 to −3 V, is the tuning parameter. A finite-size scaling analysis was used to analyze the superconductor–insulator phase transition, which gives a critical resistance of 14–17 kΩ and a critical exponent of zν ≈ 1.3–1.4. These values are comparable with those obtained in previous studies on ultrathin clean cuprate films gated by ionic liquid. [ABSTRACT FROM AUTHOR]

We demonstrate fluorine intercalation into Bi2Sr2CaCu2O8+x (BSCCO) flakes, as thick as 100 nm, by back-gating a single crystalline LaF3 substrate. Element-sensitive analysis not only confirms the presence of fluorine in BSCCO after gating but also reveals lateral diffusion of fluorine in BSCCO. Transport measurements further demonstrate the hole-doping effect of fluoride ions in BSCCO through effective modulation of the superconducting transitions. Our work introduces a distinct type of ions (F−) that can be intercalated into materials via solid state back-gating. It broadens the toolbox of ion back-gating and is useful for addressing exotic phenomena in the heavily hole doped regime. [ABSTRACT FROM AUTHOR]

While it is known that a resonant amplification of T c in two-gap superconductors can be driven by using the Fano–Feshbach resonance tuning the chemical potential near a Lifshitz transition, little is known on tuning the T c resonance by cooperative interplay of the Rashba spin–orbit coupling (RSOC) joint with phonon mediated (e-ph) pairing at selected k-space spots. Here, we present first-principles quantum calculation of superconductivity in an artificial heterostructure of metallic quantum wells with 3 nm period where quantum size effects give two-gap superconductivity with RSOC controlled by the internal electric field at the interface between the nanoscale metallic layers intercalated by insulating spacer layers. The key results of this work show that fundamental quantum mechanics effects including RSCO at the nanoscale [Mazziotti et al., Phys. Rev. B, 103, 024523 (2021)] provide key tools in applied physics for quantitative material design of unconventional high temperature superconductors at ambient pressure. We discuss the superconducting domes where T c is a function of either the Lifshitz parameter (η) measuring the distance from the topological Lifshitz transition for the appearing of a new small Fermi surface due to quantum size effects with finite spin–orbit coupling and the variable e-ph coupling g in the appearing second Fermi surface linked with the energy softening of the cut off ω 0. [ABSTRACT FROM AUTHOR]

We report single-phase superconducting face-centered cubic (FCC) intermetallic high-entropy alloys (HEAs) synthesized via splat cooling. The technique gives incredibly sharp diffraction peaks and superconducting transitions in resistivity measurements than reported in conventional arc melting. The single-phase materials fall at electron counts in the HEA superconductor alloy family where structural stability and optimal superconducting electron counts clash. The materials' superconducting properties follow the general trends published for metallic alloys. Insights are provided as to why an FCC structure may be stable. [ABSTRACT FROM AUTHOR]

Transition metal compounds with kagome structure have been found to exhibit a variety of exotic structural, electronic, and magnetic orders. These orders are competing with energies very close to each other, resulting in complex phase transitions. Some of the phases are easily observable, such as the charge density wave (CDW) and the superconducting phase, while others are more challenging to identify and characterize. Here we present magneto-transport evidence of a new phase below ~ 35 K in the kagome topological metal CsV3Sb5 (CVS) thin flakes between the CDW and the superconducting transition temperatures. This phase is characterized by six-fold rotational symmetry in the in-plane magnetoresistance (MR) and is connected to the orbital current order in CVS. Furthermore, the phase is characterized by a large in-plane negative magnetoresistance, which suggests the existence of a three-dimensional, magnetic field-tunable orbital current ordered phase. Our results highlight the potential of magneto-transport to reveal the interactions between exotic quantum states of matter and to uncover the symmetry of such hidden phases. Recent studies reported evidence of a new phase in the kagome metal CsV3Sb5 between the charge density wave and superconducting transitions. Here the authors reveal symmetry properties of this phase in CsV3Sb5 thin flakes probed by in-plane magnetotransport, suggesting a 3D orbital current order. [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]

Detection of structural and transport inhomogeneities in superconducting thin films using the standard four-probe method requires multiple measurements and may be inaccurate. A new approach to extract the information about the inhomogeneous transition into the superconducting state using van der Pauw technique is presented. The proposed method is applied to an electrochemically-reduced In-Sn-oxide (ITO) films known to be simultaneously transparent and superconducting. Relationship between the processing parameters and superconducting characteristics of the ITO films is considered, and prospects for using such samples in integrated photonic-superconducting chips for quantum-information processing are discussed. [ABSTRACT FROM AUTHOR]

Superconducting phase transitions in two dimensions lie beyond the description of the Ginzburg-Landau symmetry-breaking paradigm for three-dimensional superconductors. They are Berezinskii-Kosterlitz-Thouless (BKT) transitions of paired-electron condensate driven by the unbinding of topological excitations, i.e. vortices. The recently discovered monolayers of layered high-transition-temperature (⁠|${{{T}}}_{{\rm C}}$|⁠) cuprate superconductor Bi2Sr2CaCu2O8+δ (Bi2212) meant that this 2D superconductor promised to be ideal for the study of unconventional superconductivity. But inhomogeneity posed challenges for distinguishing BKT physics from charge correlations in this material. Here, we utilize the phase sensitivity of scanning superconducting quantum interference device microscopy susceptometry to image the local magnetic response of underdoped Bi2212 from the monolayer to the bulk throughout its phase transition. The monolayer segregates into domains with independent phases at elevated temperatures below |${{{T}}}_{{\rm C}}$|⁠. Within a single domain, we find that the susceptibility oscillates with flux between diamagnetism and paramagnetism in a Fraunhofer-like pattern up to |${{{T}}}_{{\rm C}}$|⁠. The finite modulation period, as well as the broadening of the peaks when approaching |${{{T}}}_{{\rm C}}$| from below, suggests well-defined vortices that are increasingly screened by the dissociation of vortex-antivortex plasma through a BKT transition. In the multilayers, the susceptibility oscillation differs in a small temperature regime below |${{{T}}}_{{\rm C}}$|⁠ , consistent with a dimensional crossover led by interlayer coupling. Serving as strong evidence for BKT transition in the bulk, we observe a sharp jump in phase stiffness and paramagnetism at small fields just below |${{{T}}}_{{\rm C}}$|⁠. These results unify the superconducting phase transitions from the monolayer to the bulk underdoped Bi2212, and can be collectively referred to as the BKT transition with interlayer coupling. [ABSTRACT FROM AUTHOR]

DIffuse X-ray Explorer (DIXE) is a proposed high-resolution X-ray spectroscopic sky surveyor on the China Space Station (CSS). DIXE will focus on studying hot baryons in the Milky Way. Galactic hot baryons like the X-ray emitting Milky Way halo and eROSITA bubbles are best observed in the sky survey mode with a large field of view. DIXE will take advantage of the orbital motion of the CSS to scan a large fraction of the sky. High-resolution X-ray spectroscopy, enabled by superconducting microcalorimeters based on the transition-edge sensor technology, will probe the physical properties (e.g., temperature, density, elemental abundances, kinematics) of the galactic hot baryons. This will complement the high-resolution imaging data obtained with the eROSITA mission. Here we present the preliminary design of DIXE. The payload consists mainly of a detector assembly and a cryogenic cooling system. The key components of the detector assembly are a microcalorimeter array and frequency-domain multiplexing readout electronics. To provide a working temperature for the detector assembly, the cooling system consists of an adiabatic demagnetization refrigerator and a mechanical cryocooler system. [ABSTRACT FROM AUTHOR]

Analysis of the superconducting properties of transition metal dichalcogenides (TMDs) under high pressures offers valuable insights to guide the design and synthesis of high‐performance superconducting materials. Herein, the effect of pressure is investigated on the superconductivity of a typical van der Waals layered TMDs material, PdSSe, by measuring its transport properties. After initially increased pressure, superconductivity emerges at 10.2 GPa, with a critical superconducting temperature (Tc) of ≈5.1 K, accompanied by the diminishing charge density wave (CDW) that is originally strengthening. Then, the Tc gradually increases with increasing pressure, reaching 12.1 K at the maximum pressure. The study provides experimental evidence for the superconductivity of PdSSe, and to the best of the knowledge, this is the first report on the observation of amplified CDW phenomena under increasing pressure in nonmagnetic TMDs. The abnormal enhancement of CDW transition temperature at low pressure is consistent with the upward trend of resistance, which is related to the electron–electron interaction. Moreover, synchrotron X‐ray diffraction experiments reveal two additional structural phase transitions. [ABSTRACT FROM AUTHOR]

The condensed matter Bose system may contain effective monopole quasiparticles in its excitation spectrum. In this paper, we first accomplish the mapping of the two-band Ginzburg–Landau theory to the extended CP1 model, and then perform the Monte Carlo simulations on the 50 × 50 × 50 cubic lattice with periodic boundary conditions. With the numerical data of monopole density and magnetic susceptibility, we indicate that there exists a monopole–antimonopole deconfinement transition for the two-band superconducting system with the critical temperature above 70 K. We also suggest the possible detection of this new monopole plasma phase in high- T c iron-based superconductors. [ABSTRACT FROM AUTHOR]

In this paper, we study the key and challenging issues arising in the physics of doped cuprate superconductors, which depending on the doping level (or the Fermi energy ε F ) and the characteristic energy ε A of the attractive interaction between the charge carriers (holes or electrons) might be either in the limit of fermionic (weakly-bound) Cooper pairs just like in ordinary metals or in the limit of bosonic (tightly-bound) Cooper pairs. We argue that the underlying mechanism of superconductivity in doped cuprates depends on the fermionic or bosonic nature of Cooper pairs. We examine the validity criterion of the Bardeen–Cooper–Schrieffer (BCS)-like theory of Fermi-liquid superconductivity in these materials and determine the doping level at which this criterion is well satisfied. We find that the specific overdoped cuprates (with ε F ≫ ε A or ε F > 0. 3 eV) can become the BCS-type superconductors. Using a pertinent BCS-like pairing theory, we calculate the superconducting order parameter (defined as a BCS-like gap Δ BCS ) and the critical temperature T c of the superconducting transition and the doping dependences of Δ BCS and T c in various overdoped cuprates. Our results for Δ BCS and T c in specific overdoped cuprates are in fair agreement with the experimental findings reported for these systems. [ABSTRACT FROM AUTHOR]

Radical-cation salts of formula β?-(BEDT-TTF)4[(H3O)Fe(C2O4)3]·guest have produced a large number of superconductors and provided a route to introduce magnetism and chirality into the same multifunctional material. A relationship has been found in these salts between the length of the b axis and the superconducting Tc. Increasing the b axis length by introducing larger guest molecules, such as benzonitrile and nitrobenzene, gives the highest superconducting Tcs in this family of salts. Smaller guests such as pyridine show no superconducting transition, whilst asymmetrical guests which are larger than nitrobenzene have given a different bilayered structure. Other potential guest molecules have been limited by their ability to be used as the solvent in which the crystals are grown via electrocrystallisation. This paper reports a method which introduces guest molecules into the crystal which are a solid or liquid additive within the crystal-growing solvent 1,2,4-trichlorobenzene:ethanol. We present the crystal structures of five new BEDT-TTF radical-cation salts with tris(oxalato)ferrate anions using guest molecules toluene, phenol, benzaldehyde, 4-bromobenzaldehyde, and kojic acid. [ABSTRACT FROM AUTHOR]

The transition-edge sensor (TES) as a type of low-temperature superconducting detector offers superior sensitivity due to its low thermal noise. In this work, we present a prototype TES bolometer designed for cosmic microwave background (CMB) polarization measurements. This TES is made of aluminum doped with a low concentration of manganese (2000 ppm by atomic percentage), and is deposited on the SiNx membrane which connects to the silicon substrate via narrow legs. In order to calculate its electrothermal parameters we have performed dark characterizations, which include measuring voltage-current (IV) curve at different bath temperatures, square-wave time response at various bias voltages, and noise level. This TES bolometer shows a noise equivalent power (NEP) of about 5 × 10 - 17 W/ Hz , which meets the requirement of CMB observation. However, its saturation power is smaller and time constant is larger than what are expected. We have analyzed the reasons and will make corresponding improvements in our future work. [ABSTRACT FROM AUTHOR]

Superconducting non-granular quasi-one-dimensional (1D) NbN nanowires and relatively wide granular wires of the same material exhibit similar magneto-transport behavior arising from different physical origin. Both types of wires exhibit a broad transition into the superconducting state with non-vanishing resistance well below Tc, and negative magnetoresistance (nMR) decreasing in magnitude with temperature. A distinct behavior between the two wires is revealed in their response to increasing current. In V-I measurements, the 1D wires exhibit finite initial slope, i.e., zero critical current, at all temperatures below the transition, while the granular wires exhibit a nonzero critical current that depends on temperature. Also, the two wires differ from each other in the current dependence of the nMR. In the 1D wires, at low temperature, the nMR decreases monotonically with the current, while in the granular wires the nMR initially increases with the current. The different current response of the two types of wires indicates the different physical origin of their behavior: That of the 1D wires is attributed to fluctuations of the order parameter, while that of the granular wires reflects the response of an inhomogeneous chain of Josephson junctions. [ABSTRACT FROM AUTHOR]

We studied the influence of the superconducting state on the magnetic properties in a thick IrMn(100 nm)/NiFe(100 nm) bilayer deposited by magnetron sputtering onto an yttrium–barium–copper–oxide (YBCO) substrate that was previously synthesized by the acetate method. The results from magnetization experiments showed that the sign of the effective exchange fields switched from positive, in the as-prepared heterostructure, to negative values when the sample goes below the superconducting temperature of the YBCO substrate. We, thus, demonstrated that the YBCO substrate, in its superconducting state, strongly influences the magnetic anisotropy of the thick ferromagnetic NiFe layer due to the proximity effect that occurs at the YBCO–NiFe interface, where a non-collinear magnetic spin structure is formed during the in-field sample deposition. [ABSTRACT FROM AUTHOR]

Achieving a compound with interesting multiple coexisting states, such as electride, metallicity, and superconductivity, is of great interest in basic research and practical application. Pressure has become an effective way to realize high-temperature superconductivity in hydrides, whereas most electrides are semiconducting or insulating at high pressure. Here, we have applied swarm-intelligence structural search to identify a hitherto unknown C2/m Li10Se electride that is superconducting at high pressure. More interestingly, Li10Se is estimated to exhibit the highest Tc value of 16 K at 50 GPa, which is the lowest pressure among Li-based chalcogen electrides. This superconducting transition is dominated by Se-related low frequency vibration modes. The increasing electronic occupation of the Se 4d orbital and the decreasing amount of interstitial anion electrons with pressure heighten their coupling with low-frequency phonons, which is responsible for the enhancement of the Tc value. The finding of Li-based chalcogen superconducting electrides provides a reference for the realization of other superconducting electrides at lower pressures. [ABSTRACT FROM AUTHOR]