Physics

ABSTRACT The practical deployment of electrocaloric solid‐state cooling is hindered by a critical materials challenge: achieving a large ΔT ad over a broad, stable temperature range without requiring excessive electric fields. Here, we overcome this limitation through B‐site medium‐entropy engineering in a relaxor ferroelectric multilayer ceramic capacitor (MLCC). The designed Pb(Sc 0.25 Ta 0.25 In 0.25 Nb 0.25 )O 3 MLCC exhibits a giant directly‐measured ΔT ad of 9.34 K under a moderate field of 370 kV cm −1 , which remains stable across a 90 K temperature window and withstands over 10 6 field cycles. This performance sets a new benchmark for lead‐based dielectric MLCCs. Through atomic‐scale imaging and phase‐field simulation, we reveal that the equimolar medium‐entropy configuration induces synergistic octahedral distortions and polarization nanoregions (PNRs), flattening the free‐energy landscape and significantly reducing the polarization‐switching barrier. This work establishes a generalizable strategy that B‐site medium‐entropy to decouple high EC strength from thermal instability, paving the way for high‐performance, practical solid‐state cooling devices.

ABSTRACT All‐solid‐state batteries employing chalcogen cathodes have emerged as promising candidates for next‐generation energy storage systems owing to their high theoretical energy densities. However, their practical application is severely hindered by sluggish solid‐state reaction kinetics. High‐entropy alloy (HEA) catalysts, featuring rich active sites, diverse atomic environments, and strong electronic synergistic effects, offer a compelling strategy to address this challenge. Herein, we propose a d‐p energy‐level‐matching strategy by aligning the d band of the HEA catalyst with the p band of the chalcogen cathode to enhance catalyst–cathode electronic compatibility and regulate solid‐state catalytic conversion reactions. Theoretical calculations reveal that, among the investigated HEA catalysts (FeCoNiCuX, X = Cr, Mo, and W), FeCoNiCuCr exhibits the smallest d‐p energy level gap with chalcogen cathodes, especially Se‐based chalcogenides. Such a well‐matched electronic structure maximizes interfacial charge transfer and effectively accelerates the solid–solid conversion kinetics. As a result, the optimized Se‐based electrode delivers a highly stable reversible capacity of 657 mAh g −1 after 1800 cycles at 2C. This work elucidates the key catalytic role of energy‐level‐matching catalysts for all‐solid‐state chalcogen‐based batteries and provides insight into regulating catalyst–cathode interactions to overcome the kinetic limitations in all‐solid‐state batteries with conversion‐type cathodes.

ABSTRACT The all‐inorganic metal halide perovskite CsPbI 3 is a promising photovoltaic absorber owing to its thermal stability and suitable bandgap for tandem applications. The most common approach to depositing CsPbI 3 from solution is based on the use of dimethylammonium iodide (DMAI); however, removing DMAI during crystallization is challenging, as it introduces residues that can lead to higher defect densities and trigger degradation. Here, we introduce a reaction‐guided crystallization strategy based on 2,2,2‐trifluoroethyl trifluoroacetate (TFTF), which undergoes a rapid ester‐amine amidation reaction with DMAI during annealing. By converting DMAI into highly volatile products, the TFTF reaction drives a smooth, additive residue‐free transition to γ‐CsPbI 3 and produces pinhole‐free films with low defect densities. Devices fabricated using this strategy deliver an open‐circuit voltage (V OC ) of 1.20 V and a champion efficiency of 20.8%, along with markedly improved operational stability. This intermediate‐management approach provides a practical, chemically defined pathway for directing CsPbI 3 crystallization and advancing high‐performance inorganic iodide perovskite photovoltaics.

ABSTRACT Self‐charging aqueous zinc‐ion batteries (SC‐AZIBs) represent a cutting‐edge technology that integrates energy harvesting and storage, enabling autonomous operation by utilizing ambient energy sources such as light and mechanical vibration. This review provides a systematic analysis of various self‐charging mechanisms (e.g., air, photo, thermal and mechanical self‐charging) and their advantages in specific scenarios. Through representative examples, this article delves into the design strategies for SC‐AZIB cathode materials and integrated devices, evaluating how these approaches address core scientific challenges. The key obstacles facing SC‐AZIBs are then systematically summarized, including intrinsic material limitations, system coupling efficiency, extreme environment adaptability, energy supply‐demand matching, and standardization. Finally, from a holistic innovation perspective spanning fundamental materials to system design, forward‐looking prospects are proposed to provide a theoretical foundation and viable technical pathways for the development of high‐performance SC‐AZIBs.

Abstract PdSb $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> is a metal in which band structure calculations suggest the presence of sixfold-degenerate fermions. Surface bands emerging from the sixfold-degenerate point may exhibit nontrivial topological properties. Here, we present Scanning Tunneling Microscopy (STM) measurements of PdSb $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> between 4.2 and 60 K and under magnetic fields up to 14 T. We identify a gap-like feature with a width of approximately 20 meV around the Fermi level. We additionally provide Density Functional Theory (DFT) calculations and discuss the possible connection between the observed tunneling conductance and the surface band structure. We find a small incomplete gap-like feature in the density of states which has a similar size as the feature observed in the experiment but is located slightly above the Fermi level. We furthermore estimate surface relaxation of atomic positions and find that Sb suffers larger relaxations than Pd atoms. This could influence the position in energy of the features found in the band structure. Our measurements show that PdSb $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> is a good metal, with a density of states which presents, however, interesting features close to the Fermi level.

We develop a quantum theory of negative magnetoresistance in multi-Weyl semimetals in the E ∥ B configuration, where the chiral anomaly is activated. The magnetotransport response is governed by Landau quantization and the emergence of multiple chiral Landau levels associated with higher-order Weyl nodes. These anomaly-active modes have unidirectional dispersion fixed by the node's monopole charge and dominate charge transport. As the magnetic field increases, individual chiral branches successively cross the Fermi energy, producing discrete slope changes in the longitudinal conductivity and a step-like negative magnetoresistance. This quantized evolution provides a direct experimental signature of multi-Weyl topology. Bulk Landau levels contribute only at very low fields due to strong disorder scattering and do not affect the anomaly-driven regime. Our results establish a unified, fully quantum-mechanical framework in which negative magnetoresistance arises from the discrete Landau-quantized spectrum and microscopic impurity scattering, beyond semiclassical anomaly descriptions.

The transport properties of single-molecule junctions are fundamentally governed by the energy alignment of molecular frontier orbitals relative to the electrode Fermi level. Although charging-induced reorganization is known to significantly shift this alignment, precisely how these shifts give rise to distinct transport behaviors remains elusive. Here, we use combined scanning tunneling microscopy (STM) and non-contact atomic force microscopy (AFM) at 5.5 K to investigate individual copper phthalocyanine (CuPc) molecules on a bilayer NaCl film supported by Cu(100) substrate. We identified three distinct transport phenotypes on the same substrate-characterized by behaviors ranging from elastic tunneling and dynamic charging to stable charge trapping. These phenotypes depend mainly on the reorganized orbital energy of the singly occupied molecular orbital (SOMO) relative to the substrate Fermi energy. We find that when the SOMO lies close to the substrate Fermi level, the molecule enters a sensitive charge-trapping regime in which an energy shift of only ~100 meV can change the charged-state lifetime by several orders of magnitude. This result is well captured by a theoretical model. Furthermore, we demonstrate that a pentacene molecule-functionalized tip can switch the transport behaviors. Our findings reveal how atomic-scale dielectric disorder within the moiré superlattice amplifies subtle electronic inhomogeneities into discrete transport regimes, underscoring the extreme sensitivity of molecular conductance to orbital-level alignment near the charge trapping regime and to local environmental engineering.

Abstract In this article we demonstrate that Δ T noise provides a sensitive, practical probe for distinguishing chiral edge&amp;#xD;modes from topological helical and trivial (non-topological) helical edge transport. Measured under zero-current&amp;#xD;conditions, Δ T noise reveals contrasts that conventional conductance measurements typically miss. Crucially,&amp;#xD;Δ T requires no external energy input in the form of an applied voltage bias, yet encodes the same intrinsic&amp;#xD;information that shot noise yields in the zero-temperature, finite-bias limit, without the distorting effects of&amp;#xD;Joule heating. This absence of bias-induced heating makes Δ T noise both more precise and more reliable than&amp;#xD;conventional shot-noise approaches.

Surface-supported single rare-earth atom magnets represent an ultimate limit of magnetic miniaturisation, where information storage is reduced to the scale of an individual atom. At this limit, magnetism is intrinsically quantum mechanical and governed by the interplay of strong electron correlations, crystal-field effects, and spin-orbit coupling within the localized 4f shell. In this review, we summarise and analyse recent theoretical advances in the description of rare-earth adatoms, with particular emphasis on approaches that go beyond conventional static mean-field DFT+U , which may exhibit multiple metastable solutions and treat magnetic anisotropy in a semiclassical manner. We discuss a predictive framework combining relativistic density functional theory with an Anderson impurity model treatment of the multiconfigurational 4f shell (DFT+U (HIA)), enabling a consistent description of strong correlations, multiplet structure, and quantum tunnelling effects induced by transverse crystal-field terms.As a representative case, we review the electronic structure and magnetic anisotropy of Dy adatoms on insulating MgO and spin-polarised graphene/Ni substrates. For Dy@MgO, an apparent perpendicular anisotropy is strongly reduced by quantum tunnelling driven by transverse crystal-field terms, effectively shifting the easy axis towards the surface plane. In contrast, Dy@Gr/Ni(111) realises a robust perpendicular magnetic configuration at the single-atom level. Here, the large positive magnetic anisotropy energy arises from the interplay of crystal-field splitting and strong spin-orbit coupling within the Dy 4f shell, further reinforced by the exchange field generated by the ferromagnetic Ni substrate.We argue that Dy@Gr/Ni(111) may be viewed as a limiting atomic-scale analogue of perpendicular synthetic heterostructures used in magnetic memory technologies, where exchange coupling and strong anisotropy are engineered to stabilise nanoscale bits. The insights gained from these studies establish a microscopic design principle for achieving thermally robust magnetic anisotropy at the ultimate scaling limit and highlight the broader potential of strongly correlated rare-earth adatoms for atomic-scale spintronic applications.

A two dimensional classical ferromagnetic XY model with its bound vortex-antivortex dominated quasi long range ordered phase at low temperatures is a long standing as well as well studied problem of interest in the field of condensed matter. We conduct a detailed Monte Carlo study of such model in a square lattice with rather unexplored extensions where additional anisotropic exchange coupling and Dzyaloshinskii-Moriya interactions (DMI) together affect the Kosterlitz-Thouless (KT) transition in presence/ absence of symmetry breaking fields. Without DMI, the exchange term promotes collinear (ferromagnetic) order, whereas the DMI term induces spin cantings. By tuning anisotropy upto Ising limit, we document energy, specific-heat, magnetizations as well as helicity modulus and vortex densities for different temperatures and DMI strength. We also compute the 2nd moment of correlation lengths in order to probe the spatial correlation of the spins. Furthermore, the effect of U(1) symmetry breaking 4-fold and 8-fold symmetric h4 and h8 fields are explored which shows how the double-peaked specific heat profiles changes in presence of DMI. Overall, our findings append many important updates in the low temperature phases of a topological XY ferromagnet when additional DMI and isotropy-breaking exchange and/or field terms are considered thereby providing a few practical blueprints for suitably engineering topological spin systems.

Here, we describe the distinct different anion coordination behaviors of organophosphate (PhOPO 3 2– = A) and two bis-monourea-based ligands L1 {1,1′-(1,4-phenylene)bis(3-(4-nitrophenyl)urea)} and L2 {1,1’-([1,1’-biphenyl]-4,4’-diyl)bis(3-(4-nitrophenyl)urea)}. The shorter L1 forms a hydrogen-bonded organic framework (HOF), encapsulating the counter cations in its cavities. While the longer L2 forms a rare six-stranded helicate. The formation of these structures depends on the coordinative flexibility of organophosphate and monourea. Crystal structures show that the HOF is held together by a AU 3 node (U = monourea), while the six-stranded helicate is a water bridged node AU 6 (H 2 O) that highly resembles the hydrogen bonding loop in the crystal structure of the PTP1B-pTyr assembly. This work provides critical guidance for construction of novel anion-directed assemblies based on the biomimetic hydrogen bonding between organophosphate and bis-monourea-based ligands.

Monolayer molybdenum disulfide (MoS 2 ) is a highly prominent material in optoelectronic devices, yet its intrinsic band structure limits its performance in the near-infrared regime. Here, we demonstrate a high-performance broadband photodetector based on monolayer MoS 2 hybridized with eco-friendly CuInS 2 quantum dots (CIS-QDs). The Type-II band alignment at the heterojunction interface enables efficient spatial separation of photogenerated carriers, while the CIS-QDs simultaneously passivate surface defects and induce n-type doping in the MoS 2 channel. Consequently, the device exhibits a dramatically extended photoresponse spanning ultraviolet (395 nm) to NIR (980 nm), with the photocurrent enhanced by more than 2 orders of magnitude at 980 nm relative to pristine MoS 2 . The hybrid photodetector achieves a specific detectivity (D*) exceeding 10 13 Jones at 395 and 625 nm, and a responsivity improvement of over 1 order of magnitude at 780 nm. These results validate the MoS 2 /CIS-QD heterostructure as a promising eco-friendly platform for high-performance broadband optoelectronic applications.