Disordered superconductors in low dimensions provide an exemplary manifestation for the role of quantum fluctuations in a many-body system. Specifically in Josephson arrays with comparable Josephson and charging energies ($E_J\sim E_C$), disorder tends to change the nature of the paradigmatic superconductor-insulator transition and potentially leads to formation of multiple distinct phases. We address this problem in a model of a two-legged Josephson ladder subjected to a wide spatial distribution of its parameters along the legs. In contrast, we assume the system to have a perfect ${\mathbb{Z}}_2$ symmetry to interchange between the legs, and investigate the effects of spatial randomness which preserves this symmetry in the strong-disorder limit. To this end, we apply a strong randomness real-space renormalization group technique and explore the resulting phase diagram. We identify three disorder-dominated phases, including an intermediate phase between a disordered superconductor and a disordered insulator. The latter insulating phase can be mapped to a XY spin chain in a spin-glass phase, while the intermediate phase turns out to be a Bose glass.

We consider the Bethe ansatz integrable Russian doll (RD) model of superconductivity with time-reversal symmetry breaking, which exhibits a cyclic renormalization group. By obtaining an exact solution for the renormalization group flows, we investigate the phase structure in the one-pair sector, which includes localized, fractal, and delocalized phases. We show that the quantum number $Q$, arising from the Bethe ansatz equations, counts the number of cycles and parametrizes the towers of states. Using the action of the renormalization group on the eigenstates, we demonstrate that $Q$ serves as an order parameter, providing a mechanism for the formation of the fractal phase in the deterministic systems and an example of the interplay between fractality and cyclic RG.

The thermal Hall effect (THE) is a powerful probe of material properties, even in insulators. Here, we investigate the thermal response of altermagnets by developing a theory on Berry curvature driven nonlinear THE from both electrons and magnons. We identify symmetry conditions under which the third-order THE dominates while linear and second-order contributions vanish. Notably, $d$-wave and $i$-wave altermagnets with out-of-plane Néel order satisfy these conditions, whereas in-plane order yields a dominant linear THE. Using ${\mathrm{KV}}_2{\mathrm{Se}}_2\mathrm{O}$ (a $d$-wave altermagnetic metal) and ${\mathrm{MnF}}_2$ (an altermagnetic insulator) as concrete examples, we show nonzero third-order nonlinear THE from electrons and magnons, respectively, both exhibiting a $\pi$-periodic dependence on the direction of temperature gradient. These symmetry-guaranteed Berry curvature phenomena provide a diagnostic for altermagnetism in candidate materials and enable the determination of the Néel vector orientation.

Ultrashort voltage pulses drive quantum conductors into a nonadiabatic regime where the transmitted charge can oscillate with the injected pulse charge. This effect, which we refer to as dynamic charge oscillations, has been primarily associated with interferometric devices and attributed to path interference. Remarkably, we demonstrate that, within the regime where the photoassisted description applies, this constitutes a generic phenomenon expected to emerge in any quantum conductor that exhibits a sublinear dc current at large bias. Dynamic charge oscillations, therefore, arise well beyond interferometers and remain perturbatively robust in strongly correlated conductors, including in the presence of arbitrarily strong Coulomb interactions. As a striking example, we predict this effect for a quantum point contact in Laughlin fractional edge states, demonstrating that it can occur in a genuinely noninterferometric system. We further reinterpret the phenomenon in terms of the photoassisted probabilities generated by the voltage pulse.

Conventionally, enhanced spin-orbit torque (SOT) efficiency in metallic alloy systems has been achieved by the bulk spin generation mechanism of the spin Hall effect. In this study, we investigated SOT in Au-Ti alloy. While pure Au exhibits a negligible SOT, the Au-Ti alloy exhibits a high SOT efficiency of up to 0.14. Notably, the observed SOT has a substantial interfacial contribution that is attributed to the interfacial mechanism of the Rashba-Edelstein effect. Electron transfer between Au and Ti modifies the Au $5d$ orbital, inducing a shift in energy level and a revival of orbital momentum, which in turn is associated with Rashba spin splitting. The orbital tuning mechanisms proposed in this work highlight the potential of an orbital-engineering approach for SOT.

We use thermal transport to access the electronic mean free path of $d$-wave quasiparticles in one of the most widely studied cuprate superconductors, ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ (Bi2212). We have measured the thermal conductivity ${\kappa }_{\mathrm{xx}}$ and the thermal Hall conductivity ${\kappa }_{\mathrm{xy}}$ of three single crystals across a range of dopings. In the overdoped and optimally doped samples, a clear enhancement is observed in both ${\kappa }_{\mathrm{xx}}$ and ${\kappa }_{\mathrm{xy}}$ upon cooling below the critical temperature $T_{\mathrm{c}}$, due to a suppression of the inelastic electron-electron scattering as electrons condense into pairs. The underdoped sample shows no enhancement in either, pointing to a high degree of disorder in that sample. For the two highest dopings, the magnitude of the enhancement in ${\kappa }_{\mathrm{xy}}$ is controlled by the strength of the elastic impurity scattering. Using a prior model to estimate the mean free path from ${\kappa }_{\mathrm{xy}}$ data, we find that the mean free path in Bi2212 is approximately seven times shorter than in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$, considered to be one of the least disordered cuprates. We conclude that the thermal Hall technique is a good way to compare the mean free path of $d$-wave quasiparticles in various cuprate materials.

We investigate Josephson arrays consisting of a dice-lattice network of superconducting weak links surrounding rhombic plaquettes of proximitized semiconductor. Josephson coupling of the weak links and electron density in the plaquettes are independently controlled by separate electrostatic gates. Applied magnetic flux results in an intricate pattern of switching currents associated with frustration, $f$. For depleted plaquettes, the switching current is nearly periodic in $f$, expected for a phase-only description, while occupied plaquettes yield a decreasing envelope of switching currents with increasing $f$. A model of flux dependence based on ballistic small-area junctions and diffusive large-area plaquettes yields excellent agreement with experiment, revealing how lateral proximity in semiconducting hybrids controls the crossover between film- and network-like superconductivity.

We propose a superconducting circuit based on the Bloch transistor, a quantum device consisting of two small-capacitance Josephson junctions, connected in series and having a small superconducting island in between. This device is driven by two dc electrical sources controlling Josephson oscillations of frequency $f_J=2e\overline{V_J}/h$, related to the average transistor voltage $\overline{V_J}$, and Bloch oscillations of frequency $f_B=\overline{I_B}/2e$, related to the average current $\overline{I_B}$ injected into the transistor island. We show that due to the Bloch transistor properties, these two types of oscillations are coupled and can mutually phase-lock, i.e., $f_J=f_B$. This leads to the formation of a current step on the current-voltage curve at $\overline{I_B}=2e{f}_J$, which is similar to the dual Shapiro step, appearing under microwave irradiation of frequency $f$ on the current-voltage curve of a small Josephson junction at current $I=2ef$. Moreover, the Bloch transistor transconductance $\overline{I_B}/\overline{V_J}$ takes the fundamental value of $1/R_Q$, where $R_Q=h/4e^2$ is the resistance quantum. The obtained results pave the way to an alternative quantum standard of resistance, based on the superconducting circuit and operating without applying a strong magnetic field.

Superconductivity (SC) remains a captivating field of research, promising transformative applications in energy, computing, and quantum technologies. Despite decades of investigation, the mechanisms underlying unconventional SC are not yet fully understood, motivating the discovery and study of new materials with exotic properties. The noncentrosymmetric superconductor ${\mathrm{PbTaSe}}_2$ offers a compelling platform to explore unconventional SC, where the absence of inversion symmetry can give rise to mixed-parity pairing states and novel superconducting phenomena. In this work, we investigate its superconducting properties through combination of specific-heat and muon spin relaxation ($\mu \mathrm{SR}$) measurements, with the latter performed under both ambient and applied hydrostatic pressure. At ambient pressure, ${\mathrm{PbTaSe}}_2$ exhibits a superconducting transition at ${\mathit{T}}_c=3.6\mathrm{K}$, with a normalized heat capacity jump $\mathrm{\Delta }C/\gamma {\mathit{T}}_c=1.4$, indicating weak electron-phonon coupling. A combined analysis of specific-heat and $\mu \mathrm{SR}$ data under ambient pressure reveals the presence of multigap $s+s$-wave superconductivity, characterized by two distinct superconducting gaps. Upon the application of hydrostatic pressure up to 3 kbar, ${\mathit{T}}_c$ is significantly suppressed from 3.6 K to approximately 2.5 K, likely due to structural modifications involving the shift of the Pb atomic position without any change in the overall crystal symmetry. Notably, the multigap nature of the superconducting state persists under applied pressure. Furthermore, zero-field $\mu \mathrm{SR}$ measurements confirm the absence of spontaneous internal magnetic fields at ambient as well as applied pressure, demonstrating that time-reversal symmetry remains intact in the superconducting state despite the noncentrosymmetric crystal structure of ${\mathrm{PbTaSe}}_2$. Overall, these findings establish ${\mathrm{PbTaSe}}_2$ as a promising platform to study the unconventional SC and the interplay between multigap behavior, topology, and electron-phonon coupling under pressure.

Diamond anvil cell synchrotron x-ray diffraction experiments, molecular dynamics, density functional theory, and Lindemann melting theory were used to investigate the compressibility and melting properties of $\mathrm{Ce}{\mathrm{H}}_{2-3}$. Ambient-temperature synchrotron x-ray diffraction measurements were made in diamond anvil cells up to a peak pressure of 20 GPa and show no indication of a first-order phase transition over this pressure range. Equation-of-state fits to the diamond anvil cell data constrain the isothermal bulk modulus, $B_0$, to the range 76.7(51)–87.2(39) GPa. Molecular dynamics and density functional theory were employed to simulate compression curves to a peak pressure of $\sim 30$ GPa, and constrain $B_0$ to the range 71.6(12)–81.9(12) GPa. Using laser-heated diamond anvil cells, five melt points were measured at pressures between roughly 2 and 10 GPa. We report an experimentally determined zero-pressure melting temperature of 1737(75) K and $\text{d}T/\text{d}P=27\left(15\right)$ K/GPa. A high-pressure melting curve generated from molecular dynamics simulations shows linear behavior between 0.5 GPa and the peak simulated pressure of 5 GPa, with a fit slope of $\text{d}T/\text{d}P=16$ K/GPa over this range. Calculations based on Lindemann melting theory yield a zero-pressure melting temperature of 1609 K and a slope of $\text{d}T/\text{d}P=44$ K/GPa for ${\mathrm{CeH}}_2$.

Solid solutions of the rare-earth nitrides ($L{n}_{x}L{n}_{1-x}^{\prime }\mathrm{N}$, where $\mathit{Ln}, \mathit{Ln}{}^{\prime }$ are lanthanides) allow material control of the rich spin- and orbital-magnetism of the rare earths. This includes the engineering of compensation points of the net magnetic moment or net angular momentum in fully spin-aligned phases by leveraging the strong orbital contribution to the net moment. In this study, magnetometry shows that the compensated magnetic state in ${\mathrm{Dy}}_x{\mathrm{Nd}}_{1-x}\mathrm{N}$ does not form a magnetically hard material, as one might expect, and as seen in previous studies of Gd- and Sm-based solutions. Instead, we show using XMCD that the moments on the Dy and Nd ions are delicately balanced and the compensation is easily upset by an applied field.

The discovery of superconductivity in multilayer nickelates under pressure has intensified interest in understanding the magnetic and electronic properties of Ruddlesden-Popper nickelates. Using density functional theory with Hubbard corrections, we investigate the magnetic ground state, electronic structure evolution under pressure, and Sr-doping effects in ${\mathrm{La}}_2{\mathrm{NiO}}_4$. We find that at ambient pressure, tetragonal ${\mathrm{La}}_2{\mathrm{NiO}}_4$ exhibits $G$-type antiferromagnetic order with negligible interlayer magnetic coupling. Under hydrostatic pressure, the system undergoes a continuous insulator-metal transition at 50 GPa while maintaining robust magnetic order, contrasting sharply with the rapid magnetic suppression in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$. Sr doping leads to a sequence of magnetic ground states in our calculations: from $G$ type to $A$ type, to striped antiferromagnetic orders, and, eventually, to ferromagnetic order, accompanied by metallization. Furthermore, ${\mathrm{LaSrNiO}}_4$ displays weak charge and orbital orders. These results reveal the unique pressure and doping effects of single-layer nickelates and provide insights into the magnetic mechanisms underlying nickelate superconductivity.

Previous studies have shown that $\text{SU}{\left(4\right)}_1$ chiral spin liquid can emerge in the SU(4) Hubbard model on triangular lattice. A natural question then arises: What is the phase upon doping? In this work, we show the possibility that hole doping can give rise to an anyon superconductor and propose that both spinons and holons form integer quantum Hall states with opposite chiralities. Using topological field theory we demonstrate that the phase is a topological charge-$4e$ superconductor with chiral central charge $c_{-}=4$. We further identify the deconfined excitations and anyonic excitations bound to the vortex. This unusual superconductor may be realized in moiré bilayer and detected through quantized thermal Hall effect and quantum spin Hall effect.

We report a combined study of the magnetic, electrical transport, optical reflectivity, and electronic properties of single-crystalline DyPtSb, a half-Heusler antiferromagnet that orders at 2.2 K. The electrical resistivity exhibits semiconductor-like behavior and the Hall response becomes strongly nonlinear at low temperatures, indicating multiband transport with hole- and electron-type pockets. Angular magnetoresistance measurements revealed occurrence of twofold and fourfold symmetry components, both of which change sign near magnetic field of 4 T at 2 K, suggesting a field-induced modification of the electronic structure near the crossover from the antiferromagnetic to the spin-polarized regime. The optical spectroscopy revealed a temperature-dependent plasma edge and a Drude response, consistent with the bulk electrical transport data. In contrast to the characteristic feature of three-dimensional Dirac and Weyl semimetals, the optical conductivity of DyPtSb does not exhibit clear linear-in-frequency behavior at low energy. The results of ab initio electronic band-structure calculations revealed that the compound is a narrow-gap semiconductor, showing pronounced anisotropy of valence bands and strong sensitivity to magnetic polarization. DyPtSb was characterized as a multiband low-carrier antiferromagnet whose electrical transport properties are closely tied to the evolution of its electronic structure.

We theoretically investigate the eigenspectrum and excitation of terahertz (THz) electromagnetic waves in a cylindrical beam-waveguide system containing a layered superconducting shell. The system is driven by a nonrelativistic tubular electron beam, which is assumed to be charge-neutralized by a stationary ion background. This charge compensation enables rectilinear beam propagation in the absence of an external focusing magnetic field and allows the superconductor to remain in the Meissner state. Starting from a hybrid electrodynamic boundary-value formulation, we derive the general dispersion relation for coupled beam-Josephson plasma waves (JPWs). The eigenmode spectrum and beam-induced instabilities are then analyzed in detail in the quasielectrostatic slow-wave approximation. It is shown that bulk-surface JPWs can exhibit negative dispersion, which enables the development of absolute instability during their interaction with the electron beam. For surface JPWs, the propagating branch has positive dispersion, so its beam-induced excitation is associated with convective amplification rather than absolute instability. An analytical expression for the instability growth rate is derived for the absolute-instability regime. At large longitudinal wave numbers, the frequencies of the bulk-surface waves asymptotically approach the Josephson plasma frequency ${\omega }_J$. The anisotropy coefficient $\gamma$ is found to play a crucial role in the surface-JPW spectrum: the azimuthally symmetric surface mode $(n=0)$ preserves its traveling-wave character even at high anisotropy, whereas azimuthally asymmetric modes $(n\ge 1)$ degenerate into localized oscillations with frequencies close to ${\omega }_J$ due to the shunting effect caused by the high in-plane conductivity. Numerical analysis of the absolute instability of bulk-surface JPWs shows that, among the modes considered, the maximum growth rate is attained for the $n=1$ mode. A crossover is revealed in the dependence of the growth rate on the thickness of the superconducting shell. For low-azimuthal-index modes, thinner shells enhance the instability by reducing the modal energy stored in the superconducting material and increasing the effective coupling impedance, whereas for higher-order modes $(n\ge 9)$, the instability is enhanced when the shell thickness increases because thicker shells support whispering-gallery-like field distributions. These properties indicate that the proposed structure can serve as a flexible platform for tunable THz radiation sources.

Altermagnets (AMs) combine fully compensated magnetization with momentum-dependent spin splitting, yet intrinsic altermagnetic materials exhibiting exceptional valley characteristics remain scarce. Here, we identify monolayer titanium-based chalcogenide halides, ${\mathrm{Ti}}_2{X}_{2}Y$ ($X=\mathrm{F}$, Cl, Br, I; $Y$ = O, S, Se, Te), as a new family of two-dimensional (2D) altermagnetic valley materials. These monolayers exhibit robust $d$-wave altermagnetic order, semiconducting band gaps, and pronounced spin-polarized valley characteristics. We show that uniaxial strain breaks the valley degeneracy, inducing giant valley splitting together with a tunable piezomagnetic response. An in-plane electric field generates noncollinear spin currents, while spin-orbit coupling gives rise to the anomalous Hall effect, valley-selective linear dichroism, and the magneto-optical Kerr effect. These findings establish ${\mathrm{Ti}}_2{X}_{2}Y$ monolayers as a versatile platform for exploring spin- and valley-dependent electronic, optical, and transport phenomena in 2D altermagnets.

In chiral crystals, two types of phonon angular momenta have been introduced. One is crystal angular momentum (CAM) arising from the rotational or screw-rotational symmetry and the other is mechanical angular momentum (MAM) associated with the circular motion of atomic displacements about equilibrium positions. Recently, the electron-phonon coupling that respects the screw-rotational symmetry is derived, whereby the CAM between electrons and phonons is interconverted. Here, we show that, in addition to CAM, MAM can also be converted to the electronic degrees of freedom by deriving a second-order perturbative Hamiltonian proportional to phonon MAM. This finding highlights that the electronic motion is directly affected by phonon MAM, and consequently, that phonon degrees of freedom can play a crucial role in phenomena related to electronic orbital polarization.

We study the electronic and magnetic properties of monolayer ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ within the density-functional plus dynamical mean-field theory approach in the paramagnetic phase. We argue that this compound is sufficiently far from the local magnetic moment limit, demonstrating nonlinear temperature dependencies of the partial inverse local and uniform magnetic susceptibilities in a broad temperature range. We find that in the regime of moderate Coulomb interactions ($U=3–4\mathrm{eV}$), the iron atoms located above and below the Ge plane carry a substantial local magnetic moment ($\mu \gtrsim 4.5{\mu }_B$), while the iron atom located within the Ge plane does not exhibit any pronounced magnetic moment. At the same time, the exchange interaction between these two symmetry-nonequivalent types of atoms turns out to be crucial for stabilizing long-range ferromagnetic order in ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$. The estimated spin-wave stiffness and Curie temperature are in good agreement with the experimental data, indicating that a dynamical treatment of electron correlations in ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ is essential to properly describe its partially itinerant magnetic behavior.