A high superconducting critical temperature (Tc) under normal laboratory conditions in a material that is chemically simple and stable, like an elemental metal, is a hitherto unattained goal of modern science and technology. Certain elemental metals are known to display reasonably high Tc only under extraordinarily high pressures, where their spectroscopic characterization and application are tightly restricted. Here we show that a Tc exceeding 20 K can be realized on pure elemental Ce under uniaxial pressure created simply by pressing a sharp metallic needle on the metal. This is a breakthrough because pure Ce does not superconduct under ambient conditions and the application of 54 GPa of hydrostatic pressure yields only a low Tc of 1.8 K in the metal. In addition, by driving the area under the needle in a mechanically controlled way to the ballistic transport regime, we spectroscopically characterized the superconducting energy gap in a high-pressure superconducting phase and found that superconducting Ce respects the conventional Bardeen-Cooper-Shrieffer theory.

Turbostratic multilayer graphene, composed of randomly twisted and stacked graphene sheets, offers a naturally disordered yet tunable platform for exploring moiré physics beyond tedious artificial stacking. Using scanning tunneling microscopy/spectroscopy (STM/STS) and Raman analysis, we uncover a wide distribution of twist angles and stacking configurations spontaneously formed across large-area turbostratic films. In several regions, we identify overlapping incommensurate moiré patterns consistent with locally chiral trilayer stacking. We observe van Hove singularities and reconstructed Dirac-like spectra whose angle dependence supports strong interlayer electronic coherence. In the highly strained trilayered regions, we observe peaks in the local density-of states with characteristic scaling of the quantized Landau levels strikingly even in the absence of a magnetic field. They arise from the strain-induced pseudo-magnetic fields ( 26 T), making turbostratic graphene a single natural platform to explore the physics of moiré structures as well as of the pseudo-electromagnetic fields.

The development of superconducting data storage devices is one of the coveted goals for next-generation low-power electronics, and interaction between superconducting and nontrivial topological states can potentially be useful to achieve this goal. Here we show that the superconducting diboride OsB2 hosts an anisotropic superconducting order parameter along with topological surface states which are spin polarized. Through the measurement of Andreev reflection on the surface of OsB2 we find that the superconducting order parameter senses the spin polarization of the topological surface states. As a consequence, the order parameter retains the memory of the exposure to a magnetic field, leading to a magnetic-field-dependent hysteresis effect. Thus we present nanoscale metallic junctions made on the surface of OsB2 as energy-efficient superconducting memory devices.

Particle-hole symmetry of the Bogoliubov-de Gennes Hamiltonian is widely assumed to enforce bias-symmetric transport at superconducting interfaces. We show that this expectation fails generically for interfaces with finite spatial extent due to quantum interference. Using a tight-binding scattering formalism that preserves exact particle-hole symmetry, we demonstrate that propagation through an extended interface causes electrons and holes to accumulate unequal phases, leading to intrinsic bias-asymmetric conductance. The interface thereby acts as an effective Andreev interferometer with characteristic damped oscillations arising from coherent multiple reflections within the barrier. While the asymmetry originates from normal-state interference, its bias dependence is governed by the superconducting gap, which emerges as a sharp crossover scale that can be clearly resolved even when conventional coherence peaks are weak or absent. Thus we present bias asymmetry as an interferometric, spectroscopic probe of nonlocal interface physics and superconducting energy scales in hybrid and topological systems where extended interfaces are unavoidable.

The production of green H2 fuel by photocatalytic water splitting has emerged as a potential solution to mitigate challenges related to the energy crisis. The inherent electric field generated within piezoelectric materials under mechanical stress offers a promising avenue for enhancing charge separation in photocatalysis through piezo-phototronic effect. Herein, we develop a photo-piezocatalyst leveraging [Ce6(µ3-O)4(µ3-OH)4(HCOO)6]6+ cluster modification via post-synthetic multistep integration of a donor-acceptor (D-A) dyad within Ce-based MOF-808 (Ce-MOF). This supramolecular D-A charge transfer (CT) complex inside the confined nanopore of Ce-MOF functions as an efficient light-harvesting unit. Concomitantly, light-mediated electron transfer from the CT complex, results in a mixed valence Ce4+/Ce3+ state  which creates local distortion within the Ce-oxo cluster, transitioning it from an ideal cubic state to a non-centrosymmetric configuration, giving rise to piezoelectric polarization. The synergistic interplay between piezoelectric polarization and enhanced CT driven light-harvesting capabilities culminates in an ultrahigh H2 production with a rate of 12.7 mmol g-1h-1, achieved through overall water splitting under photo-piezocatalytic conditions. This work not only highlights the immense potential of MOFs as efficient catalysts for water splitting but also paves the way for harnessing both solar and mechanical energy through photo-mediated piezocatalytic reactions.

A high superconducting critical temperature (Tc) under normal laboratory conditions in a material that is chemically simple and stable, like an elemental metal, is a hitherto unattained goal of modern science and technology. Certain elemental metals are known to display reasonably high Tc only under extraordinarily high pressures where their spectroscopic characterization and application are tightly restricted. Here we show that a Tc exceeding 20 K can be realized on pure elemental Ce under uniaxial pressure created simply by pressing a sharp metallic needle on the metal. This is a breakthrough because pure Ce does not superconduct under ambient conditions and the application of 54 GPa of hydrostatic pressure yields only a low Tc of 1.8 K in the metal. In addition, by driving the area under the needle in a mechanically controlled way to the ballistic transport regime, for the first time, we spectroscopically characterized the superconducting energy gap in a high-pressure superconducting phase and found that superconducting Ce respects the conventional Bardeen-Cooper-Shrieffer (BCS) theory.

Crystalline solids exhibiting glass-like ultralow thermal conductivity while maintaining their long-range structural order are fundamental to structural chemistry, and they hold substantial potential in the field of thermoelectrics. Though often attributed to strong anharmonic interactions and complex crystal structures, the microscopic origin of the thermally insulating nature of these crystals remains unclear, necessitating an extensive evaluation of the chemical bonding, local structure, and phonon dynamics. Here, we uncover the emergence of glass-like thermal conductivity in the single crystal of AgPbSbSe3, driven by its inherent relaxor ferroelectric behavior. Synchrotron X-ray pair distribution function (X-PDF) analysis reveals local structural symmetry breaking driven by Se off-centering along the crystallographic ⟨100⟩ direction, which constitutes the polar instability. Concurrently, density functional theory (DFT) calculations corroborate the experimental findings by identifying the antiparallel vibrations of cation (Ag) and anion (Se) sublattices and the associated double-well potential energy surface, generating dipole moments that underpin relaxor ferroelectric behavior in AgPbSbSe3. The presence of randomly oriented polar nanodomains, created by local atomic distortion in the structure, facilitates the structure to shuttle between randomly oriented, multiple nearly degenerate structures in the potential energy landscape, resulting in ultralow and glass-like thermal transport in AgPbSbSe3.

The consequences of broken long-range atomic arrangement in glasses or amorphous solids are reflected in the temperature dependence of lattice thermal conductivity (κlat). However, the appearance of glassy ultralow κlat in a crystalline solid with high electrical transport like metal is unusual but can have a remarkable impact on the thermoelectric performance of a material. Here, an ultra-high thermoelectric performance is demonstrated with a maximum figure of merit, zT ≈ 2.7 (≈2.92 with Dulong-Petit heat capacity) via achieving glassy thermal transport along with significant electrical conductivity in ball milled BiSe, Pb co-doped polycrystalline Ge1.03Te followed by spark plasma sintering. The glassy thermal transport results from the inhomogeneous ferroelectric instability developed due to local polar distortions near the dopant sites, which interacts with soft polar optical modes via strain fluctuations. Resulting structural degeneracy and associated soft vibrations sink heat effectively from acoustic phonons, which along with various nanoscale defects, confine the phonon mean free path (MFP) close to the interatomic distance, rendering the thermal transport glassy. However, the material still maintains a high electrical conductivity at ambient condition due to much longer MFP of the charge carriers. A promising output power density of ≈0.8 W cm-2 for ΔT ≈441 K in double-leg thermoelectric device demonstrate the potential of this material for mid-temperature thermoelectric applications.

We report a substantial enhancement of the superconducting transition temperature (Tc) in elemental titanium through mesoscopic point-contact formation using a simple needle–anvil technique. While bulk titanium exhibits Tc≈0.4 K under ambient conditions, our point-contact measurements reveal a locally induced superconducting phase with Tc values up to 3.5 K, comparable to that achieved under hydrostatic pressures of ∼56 GPa. The enhancement is highly contact dependent, indicating a local origin, likely associated with tip-induced uniaxial strain modifying the crystal and electronic structure beneath the contact. The evolution of resistance–temperature characteristics and differential conductance spectra with temperature and magnetic field yields an H–T phase diagram consistent with conventional superconductivity. Our results demonstrate a low-cost, table-top route to stabilizing superconducting phases with elevated Tc in elemental metals without resorting to extreme pressure techniques.

With the increasing demand and rising environmental adulteration, researchers are exploring sustainable energy harvesting methods. Water‐based energy harvesting using carbonaceous matrices and 2D layered materials has gained significant attention due to their superior electrical properties at low‐dimension. This study demonstrates cobalt‐nitrogen‐doped graphene (Co‐N‐Gr) thin layers are presented as an efficient medium for harvesting energy from diverse water sources, including simulated seawater (0.6 m NaCl), rainwater, and for differentiating pH levels and detecting acidic contaminants (H 2 SO 4 and HNO 3 ) in the aquatic environment. The nitrogen‐functionalized graphene‐assisted cobalt immobilization enhances power generation by ≈108 times compared to pristine graphene (P‐Gr) without any secondary heterojunction materials. The Co‐N‐Gr matrix improves hydrophilicity, facilitating ionic interaction and charge transfer, achieving ≈2.7 nW power generation under drop‐by‐drop motion of DI water. A mechanistic understanding is developed through experimental findings supported by density functional theory calculation to identify the role of anionic (Cl − and F − ) interaction via electrical double‐layer formation. The selective higher interaction energy with HNO 3 leads to four times higher power generation than H 2 SO 4 at the same concentration, highlighting its potential for the integration of renewable energy harvesting along with rain quality detection onto a single platform for developing commercialized smart windows.

The physics of the Kagome metal LaRh_3B_2 along with its superconductivity below 2.6 K, unlike other popular Kagome metals, is not known to be significantly influenced by the electron correlations. While the indirect techniques to probe the bulk superconducting properties of LaRh_3B_2 indicate a conventional isotropic order parameter, we show that the direct spectroscopic determination of the superconducting energy gap reveals an anomalous suppression of Andreev reflection between LaRh_3B_2 and a normal metal. This observation hints to the presence of incomplete superconducting gap formation, at least along certain momentum directions, and consequent low-lying quasiparticle states. An analysis of multiple Andreev reflection spectra captured at different points on the surface of LaRh_3B_2 reveals a distribution of the superconducting energy gap which is consistent with an anisotropic superconducting order parameter.

Polar topological textures like the bubble domains, flux closures, labyrinths, etc., unlock functional responses in ferroic systems but are difficult to stabilize and control in chemically simple, solution-grown materials. Here, we show that ultra-thin, large-area CsPbBr3 nanoplatelets host room-temperature ferroelectric bubble domains whose characteristic size is tunable by thickness. Using contact resonance piezoresponse force microscopy across 125 nm-2 mu m, we observe a systematic decrease in domain size with decreasing thickness, consistent with a depolarization field-controlled stability window. Repeated scanning transforms bubbles into labyrinthine patterns, indicating metastability under weak mechanical/electrical perturbations. Upon heating, bubbles evolve into labyrinths and vanish at T-c approximate to 90 degrees C, with nucleation recovered on cooling. These results establish a controllable platform for polar topology in solvothermally grown stoichiometric perovskite, showing how thickness and temperature set boundary conditions that govern texture selection. The thickness-tunable polar textures identified here offer a route to engineer domain wall-mediated functionalities in halide perovskites.

Ferroelectric all-inorganic halide perovskites nanocrystals with both spontaneous polarizations and visible light absorption are promising candidates for designing functional ferroelectric photovoltaic devices. Three dimensional halide perovskite nanocrystals have the potential of being ferroelectric, yet it remains a challenge to realize ferroelectric photovoltaic devices which can be operated in absence of an external electric field. Here we report that a popular all-inorganic halide perovskite nanocrystal, CsPbBr3, exhibits ferroelectricity driven photovoltaic effect under visible light in absence of an external electric field. The ferroelectricity in CsPbBr3 nanocrystals originates from the stereochemical activity in Pb (II) lone pair that promotes the distortion of PbBr6 octahedra. Furthermore, application of an external electric field allows the photovoltaic effect to be enhanced and the spontaneous polarization to be switched with the direction of the electric field. Robust fatigue performance, flexibility and prolonged photoresponse under continuous illumination are potentially realized in the zero-bias conditions. These finding establishes all-inorganic halide perovskites nanocrystals as potential candidates for designing novel photoferroelectric devices by coupling optical functionalities and ferroelectric responses.

The doping dependent phase diagram of the iron pnictide systems displays diverse electronic ground states including unconventional superconductivity and magnetic ordering. From previous bulk measurements, it was argued that the superconducting phase of Ba1-xKxFe2As2 might be described within a two band formalism where superconductivity emerges with significantly different magnitudes of the pairing amplitude in the different bands. We have performed point contact Andreev reflection spectroscopy on the optimally doped system (x x = 0.4) where we found features that misleadingly mimic the signature of multiple gap amplitudes with large energy difference, when the point contacts are away from the ballistic regime. Closer to the ballistic regime, we found two types of spectra. In one type, a single superconducting gap with unusual broadening was found. The broadening might be due to the presence of multiple gap amplitudes with small energy spacing. The other kind of spectra displayed spectral features at similar to 30 meV in the normal state that gradually diminished with increasing temperature and eventually disappeared at 140 K, the spin density wave transition temperature of parent BaFe2As2. We attribute the 30 meV spectral feature to a characteristic electron-magnon interaction energy scale in the system.

Piezocatalytic water-splitting to simultaneously produce H2 and H2O2 has many potential advantages. However, the necessity to utilize materials having polar structures limits the choice of piezocatalysts. Herein, it is demonstrated that centrosymmetric BiOBr with oxygen defects can simultaneously produce H2 and H2O2 with ultrahigh efficiencies from pure and seawater without needing assistance from noble metals or scavengers. High-pressure studies confirm that there are no non-polar-to-polar phase transitions in BiOBr, though a novel isostructural phase is discovered. Computational studies reveal that oxygen vacancy distorts the BiOBr structure to induce charge-localization and polarization. Furthermore, high pressure (i) reduces carrier effective masses and (ii) increases relative O-2p contribution in the valence band maximum to assist catalysis and improve stability. The role of oxygen vacancy is confirmed by changing its concentration, which proportionally affects H2 evolution. The work paves the way for defect engineering to develop piezocatalysts from a large pool of non-polar materials. It is proposed, proved, and theoretically rationalized the possibility of using centrosymmetric systems for piezocatalytic energy harvesting, thereby extending the scope of docile phases enormously. Using BiOBr as an example, bifunctional piezocatalytic H2 and H2O2 simultaneous generation prospects from water splitting are introduced where not only the respective efficiencies are significant but it alleviates the necessity of separating H2 and O2. image

At near-parallel orientation, twisted bilayer of transition metal dichalcogenides exhibit inter-layer charge transfer-driven out-of-plane ferroelectricity that may lead to unique electronic device architectures. Here we report detailed electrical transport in a dual-gated graphene field-effect transistor placed on 3R stacked twisted bilayer of WSe2 at a twist angle of 2.1 degree. We observe hysteretic transfer characteristics and an emergent charge inhomogeneity with multiple local Dirac points as the electric displacement field (D) is increased. Concomitantly, we also observe a strong non-local voltage signal at D = 0 V/nm that decreases rapidly with increasing D. A linear scaling of the non-local signal with longitudinal resistance suggests edge mode transport, which we attribute to the breaking of valley symmetry of the graphene channel due to the spatially fluctuating electric field from the moire domains of the underlying twisted WSe2. A quantitative analysis connecting the non-locality and channel inhomogeneity suggests emergence of finite-size domains in the graphene channel that modulate the charge and the valley currents simultaneously. This work underlines efficient control and impact of interfacial ferroelectricity that can trigger a new genre of devices for twistronic applications.

While the possibility of topological superconductivity (TSC) in hybrid heterostructures involving topologically nontrivial band structure and superconductors has been proposed, the realization of TSC in a single stoichiometric material is most desired for fundamental experimental investigation of TSC and its device applications. Bulk measurements on YRuB$_2$ detect a single superconducting gap of $\sim$ 1 meV. This is supported by our electronic structure calculations which also reveal the existence of topological surface states in the system. We performed surface-sensitive Andreev reflection spectroscopy on YRuB$_2$ and detected the bulk superconducting gap as well as another superconducting gap of $\sim$ 0.5 meV. From our analysis of electronic structure, we show that the smaller gap is formed in the topological surface states in YRuB$_2$ due to the proximity of the bulk superconducting condensate. Thus, in agreement with the past theoretical predictions, we present YRuB$_2$ as a unique system that hosts superconducting topological surface states.

CsPbBr3 exhibits outstanding optoelectronic properties and thermal stability, making it a coveted material for detectors, light-emitting diodes, and solar cells. Despite observations of ferroelectricity in CsPbBr3 quantum dots, synthesizing bulk ferroelectric CsPbBr3 crystals has remained elusive, hindering its potential in next-generation optoelectronic devices like optical switches and ferroelectric photovoltaics. Here, a breakthrough is reported: a novel solvothermal technique enabling the growth of ferroelectric CsPbBr3 nanoplatelets with lateral dimensions in the tens of micrometers. This represents a significant step toward achieving large-area ferroelectric CsPbBr3 crystals. Unlike traditional methods, this approach allows for growth and crystallization of CsPbBr3 in alcohol solutions by enhancing precursor solubility. This study confirms the ferroelectric nature of these nanoplatelets using second harmonic generation, electrical characterizations, and piezoresponse force microscopy. This work paves the way for utilizing ferroelectric CsPbBr3 in novel optoelectronic devices, significantly expanding the potential of this material and opening doors for further exploration in this exciting field.

Piezocatalytic water splitting is an emerging approach for generating green hydrogen by using noise. However, while the efficiency of hydrogen production remains limited, barely anything is known about the long-term usability of the piezocatalysts. In this study, we present single-crystalline Sr2Bi3Nb2O11Br nanoplates with precise facet control and remarkable piezoelectric properties, exhibiting a significantly enhanced piezocatalytic hydrogen production rate of 5.3 mmol/g/h without needing any expensive cocatalyst, such as Pt. Furthermore, we extend the application of these nanoplates to seawater splitting with a commendable rate retention of 4.1 mmol/g/h seawater, mimicking NaCl solution and 3.5 mmol/g/h in real, unprocessed seawater, surpassing the existing piezocatalysts operated using pure water. A key finding in this work is the fatigue-resistant nature of the Sr2Bi3Nb2O11Br nanoplates originating from the layered structure. These maintain similar to 100% activity for over 150 h of continuous operation, while the existing catalysts have not been tested beyond 10-15 h, offering a sustainable approach for renewable hydrogen production.