The strange metal is a mysterious non-Fermi liquid which shows linear-in-$T$ resistivity behavior at finite temperatures, and, as found in recent experiments, vanishingly small shot noise in the linear-in-$T$ regime. Here, we investigate the shot noise of a strange metal based on a phenomenological model of marginal Fermi liquid (MFL), where fermions couple to some collective boson mode, leading to $T$-linear scattering rate at finite $T$. It is found that in the diffusive regime where the MFL scattering length is small compared to the system size, the shot noise vanishes, and the thermal noise becomes a temperature- and voltage-independent constant. Introducing additional impurity scattering increases the shot noise, and is probably consistent with the current experiment.

${\mathrm{Ni}}_{1-x}{\mathrm{V}}_x$ shows a ferromagnetic to paramagnetic quantum phase transition around the critical concentration $x_c$ = 0.12, which is masked by the cluster glass phase at very low temperatures. V doping in Ni could lead to a complex structure around the Ni atoms and hence could affect the physical properties. In this work, we investigated the structure of the alloy at both local and global levels and the origin of the ferromagnetic to paramagnetic transition at 30 K in the region above the cluster glass phase using x-ray photoemission and x-ray absorption spectroscopy and electronic structure calculations. Our Ni $3s$ and $2p_{3/2}$ core level studies suggest a reduction in the magnetic moment with $x$ and a signature of plasmon loss features, respectively. Our results suggest that the behavior of the intensity close to the Fermi level at temperatures above the masked region can be used as an indicator for $x_c$, especially in the present scenario where there is significant disorder. Our combined results obtained using the above methods suggest that Ni stabilizes in the fcc lattice at the global level and there are also clusters of Ni present at the local level. Our electronic structure calculations suggest the role played by the density of states at the Fermi level in driving the ferromagnetic to paramagnetic transition at 30 K around the critical composition, $x_c$ = 0.12. Considering the fact that Ni forms clusters at the local level, we believe that our study will be helpful in understanding the magnetism in such itinerant systems with metastable structures.

Twisting of van der Waals layered materials induces numerous exotic quantum phenomena under symmetry reduction and long-range moiré potential with strong correlation, leading to the pursuit of twistronic materials at different dimensionalities. Here we show that twisted one-dimensional (1D) atomic wires also exhibit intriguing electronic and optical features, tunable by twist angles. By analyzing transition metal trichalcogenide atomic wires, which have been synthesized in experiments, we find that a single chain of $\mathrm{WT}{\mathrm{e}}_3$ natively favors a helical structure with a short torsional wavelength of 1.58 nm and a twist angle of 24° as its energy minimum. Twisting the atomic wire azimuthally could realize a metal-to-semiconductor transition and a symmetry-protected persistent spin helix texture. In addition, we propose a light-induced pure spin current generation without a net electric charge current, indicating magnetic moment accumulation at the ends of twisted wires and a sizable spin voltage along the axial direction. These results shed light on exploiting 1D materials for twistronics and chiral spintronics.

We numerically study the first- and the second-order topological states of electromagnetic waves in the three-dimensional (3D) woodpile photonic crystal (PhC). Recent studies on 3D PhCs have mainly focused on the observation of the topological states. Here we not only focus on finding the topological states but also propose a numerical calculation method for topological invariants, which is based on the Wilson loop. For the 3D woodpile PhC, the topological states emerge due to the finite difference in the winding number or partial Chern number. The selection rule for the emergence of topological hinge states is also pointed out based on the topological invariants. Our numerical calculation results are essential and take a step toward the experimental realization of topological waveguide in 3D PhCs.

Quantum heat engines and quantum refrigerators are proposed in three-terminal quantum Hall (QH) and quantum spin Hall (QSH) setups with a voltage-temperature probe in both the linear and nonlinear transport regimes. In the linear response regime, we find that efficiency at maximum power approaches the Van den Broeck limit in both QH and QSH setups. Similarly, in nonlinear response, we find that efficiency at maximum power reaches the Whitney bounds. Interestingly, we see that in the same setup and using quantum point contacts, the thermoelectric efficiency limits in linear and nonlinear response being achieved.

Two semiconducting quantum dots (QDs) coupled through a superconductor constitute a minimal realization of a Kitaev chain with Majorana zero modes (MZMs). Such MZMs can be detected, e.g., by tunneling conductance between each QD and normal leads [Dvir et al., Nature (London) 614, 445 (2023)]. We here discuss how the seemingly trivial substitution of one of the normal leads by a superconducting (SC) one gives rise to a plethora of unique effects. In particular, the coupling to the SC lead induces nonlocal Majorana effects upon variations of the QDs' energies. Furthermore, the lowest excitation of the chain is no longer determined by the bulk gap but rather by the energy of an emergent subgap Yu-Shiba-Rusinov (YSR) state coexisting with the MZMs. The YSR state hybridizes with the MZMs when the coupling between the SC and the QD is larger than the spin splitting, spoiling the Majorana properties, including the quantized conductance.

The edges of a two-dimensional topological phase of matter serve as a platform underlying its low-energy dynamics. The topology of the bulk phase dictates the structure of the gapless modes. Proximitizing boundary modes to another boundary may lead to gap opening at the edge. Subsequently, one may engineer different segments of the boundary with intrinsic incompatibility of gap-generating mechanisms (“edge-edge incompatibility”), facilitating the generation of topological excitations, e.g., Majorana zero modes (MZMs). Here, we address the possibility of bulk-edge incompatibility, whereby the intrinsic bulk gap competes with a gap generated via boundary modes. Specifically, we consider two $\nu =2/3$ fractional quantum Hall phases whose shared boundary modes are gapped out via disorder-generated tunneling across the boundary. A “neutral superconducting” phase, made up of neutral edge modes, is stabilized over a broad range of interaction parameters. This phase cannot coexist with the bulk gap. The resulting edge-bulk incompatibility gives rise to the emergence of MZMs (in the neutral sector). We propose an experimental setup to verify both the neutral superconductivity phase and the emergent MZMs.

Motivated by recent debates around the many-body localization (MBL) problem, and in particular its stability against systemwide resonances, we investigate long-distance spin-spin correlations across the phase diagram of the random-field XXZ model, with a particular focus on the strong disorder regime. Building on state-of-the-art shift-invert diagonalization techniques, we study the high-energy behavior of transverse and longitudinal correlation functions, computed at the largest possible distance, for a broad range of disorder and interaction strengths. Our results show that while transverse correlations display a fairly stable exponential decay over the entire XXZ phase diagram, longitudinal correlations exhibit markedly different behavior, revealing distinct physical regimes. More precisely, we identify an intermediate disorder region where standard observables show well-converged MBL behavior [Colbois et al., Phys. Rev. Lett. 133, 116502 (2024)] while the distributions of longitudinal correlations reveal unexpected fat tails toward large values. These rare events strongly influence the average decay of longitudinal correlations, which we find to be algebraic in a broad region inside the supposed MBL phase, whereas the typical decay remains mostly exponential. At stronger disorder and weaker interactions, this intermediate regime is replaced by a more conventional exponential decay with short correlation lengths for both typical and average correlators, as expected for standard localization. Our findings shed light on the systemwide instabilities and raise important questions about the impact of such rare but large long-range correlations on the stability of the MBL phase. Finally, we discuss the possible fate of the intermediate region in the context of recent perspectives in the field.

Berry curvature of Bloch bands arising in lattice systems can induce a Hall response even in the absence of topology due to the so-called Berry-curvature dipole (BCD). Such a response is universal and, in principle, should occur as a thermal-Hall effect in magnon systems under the application of a temperature gradient. However, this effect intrinsically appears as a nonlinear (second-order) response to the temperature gradient making experimental detection difficult. Here we propose an alternate route to access BCD in magnons. By utilizing the process of spin-injection in conjunction with a temperature gradient, we uncover two previously unreported contributions to the BCD-induced Hall response for magnons—one that is linear in temperature gradient and the other is nonlinear in the magnon chemical potential gradient arising from spin injection. As an added benefit of our approach, both these responses extract distinct moments of the genuine BCD distribution over the magnon bands, as opposed to the recently reported extended BCD in magnons. We use Boltzmann transport theory to derive the expression for the magnon-Hall response in the presence of a thermal gradient and spin injection. Furthermore, using this expression, we offer predictions for the BCD-induced magnon-Hall effect to be observed in experiments for ferro-, antiferro-, and ferrimagnetically ordered models on various lattices, including the honeycomb lattice, the kagome lattice, and the dice lattice.

Most functional materials possess one single outstanding property and are limited to be used for a particular purpose. Instead of integrating materials with different functions into one module, designing materials with controllable multi-functions is more promising for the electronic industry. In this paper, we investigate an unexplored $\alpha$-phase of two-dimensional (2D) ${\mathrm{Mn}}_2{\mathrm{B}}_2{\left(\mathrm{OH}\right)}_2$ theoretically. Eighteen macroscopical distinct electrical polarizations, characterized by three different magnitudes and twelve different directions, are found in this phase. The switch of the electrical polarizations is also linked to an observed splitting of band structures between different spin states and the ferroelasticity of the system. The manipulation of these properties can be realized through controlling the alignment of Mn-OH-Mn chains. The diverse and tunable properties make the proposed material as an outstanding candidate for sensing applications at the 2D limit.

The lead-free piezoelectric system $\left({\mathrm{K}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\right)\left(\mathrm{M}{\mathrm{g}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}\right){\mathrm{O}}_3-\left({\mathrm{K}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\right)\mathrm{Ti}{\mathrm{O}}_3$ (KBMN-KBT) has recently been reported to show a composition-driven tetragonal ($P4mm$)- monoclinic (Pm) interferroelectric instability [Surta et al., J. Am. Chem. Soc. 143, 1386 (2021)], similar to what is known for the Pb-based piezoelectric system $\mathrm{Pb}\left(\mathrm{M}{\mathrm{g}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}\right){\mathrm{O}}_3\text{−}\mathrm{PbTi}{\mathrm{O}}_3$ (PMN-PT). This has led to the view that KBMN-KBT is a Pb-free analog of PMN-PT. We examine this view critically by analyzing the structural states of the compositions close to the proposed morphotropic phase boundary of KBMN-KBT. For the sake of generality, we also investigate the Zn-analogue series $\left({\mathrm{K}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\right)\left(\mathrm{Z}{\mathrm{n}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}\right){\mathrm{O}}_3\text{−}\left({\mathrm{K}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\right)\mathrm{Ti}{\mathrm{O}}_3$ (KBZN-KBT). In conjunction with dielectric, ferroelectric, and piezoelectric measurements, we performed structural analysis on different length scales using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy techniques. We found two different critical compositions: one corresponding to the maximum weak-field piezoelectric response ($d_{33}$) and the other corresponding to the maximum large-field converse piezoelectric coefficient ($d_{33}^{*}$). We found that unlike PMN/PZN-PT, the maximum electromechanical response in KBMN/KBZN-KBT is not associated with a symmetry-breaking structural-polar instability. The increased electromechanical response is rather caused by onset of a microstructural (domain) instability leading to the formation of short-range order ferroelectric domains of the same (tetragonal, $P4mm$) symmetry. We establish a correlation between the electrostrain response and the electric-field driven reversible short-range–long-range order transformation. Our study provides the necessary insights to appreciate the important differences between KBMN/KBZN-KBT vis-à-vis their proposed Pb-based counterparts, both from the structural and property standpoints.

Partial solvability plays an important role in the context of statistical mechanics since it has turned out to be closely related to the emergence of quantum many-body scar states, i.e., exceptional energy eigenstates which do not obey the strong version of the eigenstate thermalization hypothesis. We show that partial solvability of a bulk (closed) system Hamiltonian can lead to that of an open quantum many-body system coupled to boundary dissipators under certain conditions. We propose two mechanisms that support partially solvable structures in boundary dissipative systems: The first one is based on the restricted spectrum generating algebra, while the second one is based on the Hilbert space fragmentation. From these structures, we derive exact eigenmodes of the Gorini-Kossakowski-Sudarshan-Lindblad equation for a family of quantum spin chain models with boundary dissipators, where we find various intriguing phenomena arising from the partial solvability of the open quantum systems, including persistent oscillations (quantum synchronization) and the existence of the matrix product operator symmetry. We discuss how the presence of solvable eigenmodes affects long-time behaviors of observables in boundary dissipative spin chains based on numerical simulations using the quantum trajectory method.

The study of non-Fermi liquids sheds light on unconventional phenomena in condensed matter systems that lie beyond the scope of Landau Fermi liquid theory. One intriguing example is the Bose metal, characterized by an uncondensed bosonic ground state. However, constructing a Bose metal phase in two dimensions (2D) remains a significant challenge. Utilizing constraint path quantum Monte Carlo and functional renormalization group methods on a fermionic system with spin anisotropy in a 2D lattice, we reveal the emergence of a Cooper pair Bose metal (CPBM) phase in a highly anisotropic regime ($\alpha <0.30$) with wide range of filling, as proposed in [A. E. Feiguin et al., Phys. Rev. Lett. 103, 025303 (2009)]. Our findings exhibit a visible nonzero momentum Bose surface in the Cooper-pair distribution function, accompanied by a distinct signal of $d_{xy}$ correlation between pairs. Our results highlight that spin-dependent anisotropy in the Fermi surface leads to versatile pairing forms. Platforms such as ultracold atoms in optical lattices and recently proposed altermagnets hold promise for realizing this intriguing phase.

We unveil a mechanism for quasicondensation of hard-core bosons in the presence of quasiperiodicity-induced multifractal single-particle states. The observed phase, here dubbed a fractal quasicondensate, is characterized by natural orbitals with multifractal properties and by an occupancy of the lowest natural orbital, ${\lambda }_0\simeq L^{\gamma }$, which grows with system size but with a nonuniversal scaling exponent, $\gamma <1/2$. In contrast to fractal quasicondensates obtained when the chemical potential lies in a region of multifractal single-particle states, placing the chemical potential in regions of localized or delocalized states yields, respectively, no condensation or the usual 1D quasicondensation with $\gamma =1/2$. Our findings are established by studying one-dimensional hard-core bosons subjected to various quasiperiodic potentials, including the well-known Aubry-André model, employing a mapping to noninteracting fermions that allows for numerically exact results. We discuss how to test our findings in state-of-the-art ultracold atom experiments.

We calculate the typical bipartite entanglement entropy ${\langle S_A\rangle }_N$ in systems containing indistinguishable particles of any kind as a function of the total particle number $N$, the volume $V$, and the subsystem fraction $f=V_A/V$, where $V_A$ is the volume of the subsystem. We expand our result as a power series ${\langle S_A\rangle }_N=afV+b\sqrt{V}+c+o\left(1\right)$, and find that $c$ is universal (i.e., independent of the system type), while $a$ and $b$ can be obtained from a generating function characterizing the local Hilbert space dimension. We illustrate the generality of our findings by studying a wide range of different systems, e.g., bosons, fermions, spins, and mixtures thereof. We provide evidence that our analytical results describe the entanglement entropy of highly excited eigenstates of quantum-chaotic spin and boson systems, which is distinct from that of integrable counterparts.

Motivated by the discovery of high-temperature superconductivity in bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ under pressure, we investigate the ground-state phase diagram and correlation effects using determinant quantum Monte Carlo simulations in a simplified bilayer two-orbital Hubbard model at half filling. Our results reveal the emergence of a nonmagnetic weakly insulating phase at weak on-site Hubbard interactions, transitioning to an antiferromagnetic Mott insulating phase as the interaction strength exceeds a critical value $U/t_1^x\approx 4.15$. This phase transition is consistent with the 3D O(3) Heisenberg universality class. Additionally, we analyze dynamical properties such as the single-particle spectral function and dynamic spin structure factor. The pronounced interlayer correlation of $d_{3z^2-r^2}$ orbitals results in a downward trend and an extended flatness in the $\gamma$ band, mirroring the angle-resolved photoemission spectroscopy findings under ambient pressure. Our numerical results provide important clues for understanding the strong correlation effects in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$.

Layered perovskites of general formula AA'${\mathrm{CuFeO}}_5$ are characterized by the presence of spiral magnetic phases whose ordering temperatures $T_{\mathrm{spiral}}$ can be tuned far beyond room temperature by introducing modest amounts of Cu/Fe chemical disorder in the crystal structure. This rare property makes these materials prominent candidates to host multiferroicity and magnetoelectric coupling at temperatures suitable for applications. Moreover, it has been proposed that the highest $T_{\mathrm{spiral}}$ value that can be reached in this structural family ($\sim 400$ K) corresponds to a paramagnetic-collinear-spiral triple point with potential to show exotic physics. Since generating high amounts of Cu/Fe disorder is experimentally difficult, the phase diagram region beyond the triple point has been barely explored. To fill this gap we investigate here eleven ${\mathrm{YBa}}_{1-x}{\mathrm{Sr}}_x{\mathrm{CuFeO}}_5$ solid solutions ($0\le x\le 1$ ), where we replace Ba with Sr with the aim of enhancing the impact of the experimentally available Cu/Fe disorder. Using a combination of bulk magnetization measurements, synchrotron x-ray and neutron powder diffraction we show that the spiral state with ${\mathbf{k}}_s=(\frac{1}{2},\frac{1}{2},\frac{1}{2}\pm \mathit{q})$ is destabilized beyond a critical Sr content, being replaced by a fully antiferromagnetic state with ordering temperature $T_{\mathrm{coll}2}\ge T_{\mathrm{spiral}}$ and propagation vector ${\mathbf{k}}_{c2}=(\frac{1}{2},\frac{1}{2},0)$. Interestingly, both $T_{\mathrm{spiral}}$ and $T_{\mathrm{coll}2}$ increase with $x$ with comparable rates. This suggests a common, disorder-driven origin for both magnetic phases, consistent with theoretical predictions.

${\mathrm{Fe}}_x\mathrm{Te}$ thin films were prepared on ${\mathrm{SrTiO}}_3$ (001) substrates by molecular beam epitaxy in a well-ordered epitaxial layer-by-layer fashion. The composition of the films was varied by adjusting the Te flux in a Te-limited growth regime. Changes in the electronic structure were systematically studied using in situ x-ray absorption spectroscopy at the Fe $L_{2,3}$ and Te $M_{4,5}$ edges and x-ray photoelectron spectroscopy of core levels and valence band. We found that FeTe with optimized composition (Fe/Te ratio $\approx$ 1) provides the sharpest spectral features, indicating that ${\mathrm{Fe}}_{1.00}\mathrm{Te}$ can be synthesized as a thin film, although it is not possible in bulk.