Electron transport in Weyl semimetals has attracted significant attention in the condensed matter community due to the solid-state realization of Weyl fermions. While magnetotransport in in pseudospin-1/2 (Weyl) systems is well established, its extension to higher-pseudospin fermions remains a frontier with critical implications for transport phenomena in materials with multifold fermions. We present a rigorous quasiclassical analysis of longitudinal magnetotransport in pseudospin-1 fermions, advancing beyond conventional models that assume constant relaxation times and neglect the orbital magnetic moment and global charge conservation. Our study uncovers a magnetic-field dependence of the longitudinal magnetoconductance: it is positive and quadratic in $B$ for weak internode scattering and transitions to negative values beyond a critical internode scattering strength. Notably, the critical threshold is lower for pseudospin-1 fermions compared to their pseudospin-1/2 counterparts. We show analytically that the zero-field conductivity is affected more strongly by internode scattering for pseudospin-1 fermions than conventional Weyl fermions. Furthermore, we extend our study to fourfold-degenerate fermions (pseudospin 3/2), which exhibit multiple Fermi surfaces, and uncover the nuanced nature of magnetotransport arising from distinct scattering channels. These insights provide a foundational framework for interpreting recent experiments on multifold fermions and offer a road map for studying magnetotransport in candidate materials with space group symmetries 199, 214, and 220.

The semiclassical Boltzmann equation is widely used to study transport effects. However, being semiclassical and borrowing heavily from classical mechanics, the formalism calls for verification from the perspective of quantum mechanics. Although previous works discussed the relation between the quantum density matrix and the semiclassical formalism, direct comparison, especially of disorder effects, including side jumps and skew scattering in the two approaches, has not been fully conducted. In this work, we systematically and directly compare the semiclassical Boltzmann equation and its counterpart arising from the density matrix. We find that there is an additional correction to the side-jump velocity, the longitudinal velocity, which is longitudinal in the leading order, and its resultant current does not require time-reversal symmetry breaking. Moreover, we find the semiclassical side-jump collision integral is an approximation of the quantum result at moderate temperatures, and it also contains a correction induced by the longitudinal velocity. We also show that the scattering rate obtained from the density matrix agrees with the semiclassical results. Our work illuminates the quantum roots of the semiclassical Boltzmann equation.

Recently, some $Z_2$ monopole charges were defined for Dirac semimetals with $\mathcal{GT}$ symmetry ($\mathcal{G}$: glide, $\mathcal{T}$: time-reversal) in previous works, and the charges are believed to lead to double helicoid surface states. However, no proof of the bulk-surface correspondence is given there. In this paper, we define a generalized $Z_2$ charge, which enables us to find various properties of $\mathcal{GT}$-protected Dirac semimetals. Then, by using the $Z_2$ charge, we give a proof of the bulk-surface correspondence. We also show that the new $Z_2$ charge is equal to the $Z_2$ invariant for $\mathcal{G}$-protected topological crystalline insulators, and to the second Stiefel-Whitney number for $\mathcal{PT}$-protected nodal line semimetals, under some symmetries.

In pursuing room-temperature quantum hardware, our study introduces the effect of tunable photodoping in gate-bias assisted quantum wire within a trigated architecture of an $n$-type junctionless metal-oxide-semiconductor field-effect transistor. To comprehend this behavior, we developed a theoretical model based on a nonequilibrium Green's function formalism. Our findings demonstrate the transition of the device from a semiclassical to a quantum domain under gate influence, with optical occupancy of electronic subbands at room temperature. Tunable photodoping originates from varying resonant excitations due to reallocation of interacting states between valence and conduction bands. Gate bias causes centralization of electrons, which experience reduced interfacial trouble, resulting in distinct current peaks for specific gate biases compared to dark conditions at various drain voltages. This study underscores the persistence of quantum confinement effects via semiclassical transport, even at room temperature.

Interacting one-dimensional bosons with long-range hopping decaying as a power law $r^{-\alpha }$ with distance $r$ are considered with the renormalization group and the self-consistent harmonic approximation. For $\alpha \ge 3$, the ground state is always a Tomonaga-Luttinger liquid, whereas for $\alpha <3$, a ground state with long-range order breaking the continuous global gauge symmetry becomes possible for sufficiently weak repulsion. At positive temperatures, continuous symmetry breaking becomes restricted to $\alpha <2$, and for $2<\alpha <3$, a Tomonaga-Luttinger liquid with the Tomonaga-Luttinger exponent diverging at low temperatures is found.

We demonstrate that a boundary defect in the single spin-$\frac{1}{2}$ quantum XX chain exhibits two-channel Kondo physics. Due to the presence of the defect, the edge spin fractionalizes into two Majorana fermions, out of which one decouples, and one is overscreened by the free fermion in bulk, leading to nontrivial boundary behavior characteristic of the two-channel Kondo model. When the boundary-to-bulk coupling ratio exceeds a critical value of $\sqrt{2}$, a massive boundary-bound mode is exponentially localized near the impurity site for strong impurity coupling. This leads to unusual behavior in physical quantities, such as the $g$ function not being monotonic. We compute the $g$ function of the impurity from thermodynamic and entanglement entropy calculations and show that it takes a noninteger value of $\sqrt{2}$ just as in the two-channel Kondo problem.

We propose a mechanism of current-induced phonon angular momentum, which we call phonon Edelstein effect. We investigate this effect in three-dimensional chiral metals with spin-orbit coupling and chiral phonons, and obtain an analytical expression of phonon angular momentum induced by the current. We also discuss the physical interpretation of this effect and give an estimation of its magnitude.

We present a method to numerically obtain low-energy effective models based on a unitary transformation of the ground state. The algorithm finds a unitary circuit that transforms the ground state of the original model to a projected wave function with only the low-energy degrees of freedom. The effective model can then be derived using the unitary transformation encoded in the circuit. We test our method on the one-dimensional and two-dimensional square-lattice Hubbard model at half-filling and obtain more accurate effective spin models than the standard perturbative approach.

The exciton condensate, a counterpart of superconductors realized in two-dimensional quantum Hall bilayer systems, has yet to demonstrate definitive experimental evidence of phase coherence such as the Josephson effect. This work introduces a gate-defined Josephson junction designed to exhibit the in-plane Josephson effect in van der Waals heterostructures. Unlike superconducting S-I-S junctions, the proposed device leverages a nearly layer-polarized gated region to mediate Josephson coupling via layer pseudospin variation. This coupling mechanism is tunable through gate voltages and magnetic fields, offering a high degree of experimental control. We demonstrate the feasibility of the design using realistic parameters, paving the way for direct observation of excitonic phase coherence in clean quantum Hall systems.

In this work, we focus on the critical dynamics of the one-dimensional quasiperiodic $p$-wave-paired Aubry-André-Harper model, which exhibits a transition point between the gapped critical and the gapless localized phases. First, we disclose that the dynamical exponent features two distinct plateaus in the gapless localized phase. Besides the plateau with dynamical exponent $z=1.388$ near the transition point, there is a second one with $z=1$ away from the transition point. Then we demonstrate that these two plateaus intrinsically affect the critical dynamics with moderate quench rate by employing both one-way and round-trip quench protocols. In the one-way quench protocol, we clarify that the Kibble-Zurek (KZ) regime consists of two subregimes with different KZ exponents, which is a direct consequence of the two-plateau structure of the dynamical exponent. We also diagnose the KZ, presaturated, and saturated regimes by varying the quench rate from slow to fast limits while, in the round-trip quench protocol, we observe the defect density exhibits a clear oscillatory interference pattern with a steady period within the KZ regime. More intriguingly, a bottleneck appears in the pattern, which reflects the turning of the two KZ subregimes.

We report high-field magnetization, magnetostriction, and electric polarization studies on single crystals of $\mathrm{SmM}{\mathrm{n}}_2{\mathrm{O}}_5$. When the magnetic field is applied along the $a$- and $b$-axes, the magnetization increases linearly up to 60 T, whereas for H//c, the magnetization exhibits several successive metamagnetic phase transitions at $H_1\sim 22.2$ T, $H_2\sim 48.5$ T, and $H_3\sim 55.8$ T, with an additional transition at higher critical magnetic fields ($H_4$) above 7 K. These transitions are accompanied by changes in electric polarization, suggesting a strong magnetoelectric coupling effect. An intriguing phenomenon is the sign reversal of electric polarization above $H_4$ relative to the low-field phase, which may be attributed to the modulation of the antiferromagnetic Mn chains by the high magnetic field. The resulting complex phase diagram reveals significant magnetoelectric anisotropy driven by the magnetic field along the $a$- and $c$-axes. These studies provide a deeper understanding of the underlying physics in the multiferroic $R\mathrm{M}{\mathrm{n}}_2{\mathrm{O}}_5$ family.

The anomalous Hall effect (AHE) is a topology-related transport phenomenon of potential interest in spintronics because this effect enables the efficient probe of magnetic orders (i.e., data readout in memory devices). It is well-known that AHE spontaneously occurs in ferromagnets or antiferromagnets with magnetization. While recent studies have revealed electric-field induced AHE (via linear magnetoelectric coupling), an AHE originating from nonlinear magnetoelectric coupling remains largely unexplored. Here, by symmetry analysis, we establish the phenomenological theory regarding the spontaneous and electric-field driven AHE in magnets. We show that a large variety of magnetic point groups host an AHE that is driven by uniaxial, biaxial, or triaxial electric field and that comes from nonlinear magnetoelectric coupling. Such electric-field driven anomalous Hall conductivities are reversible by reversing the magnetic orders. Furthermore, our first-principles calculations suggest ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and ${\mathrm{CoF}}_2$ as candidates hosting the aforementioned AHE. Our work emphasizes the important role of nonlinear magnetoelectric coupling in creating exotic transport phenomena and offers alternative avenues for the probe of magnetic orders.

A robust and efficient model for investigating the ultrafast dynamics of magnetic materials excited by laser pulses has been created, integrating dynamic Landau-Lifshitz-Bloch equations with a quantum thermostat and a two-temperature model. The model has been successfully applied to three archetypal materials in the literature: nickel, cobalt, and iron. Additionally, analysis of the ultrafast dynamic susceptibility tensor indicates that off-diagonal components display specific features depending on whether a continuous external magnetic field is present.

Iron borate ($\mathrm{FeB}{\mathrm{O}}_3$) is a unique material that simultaneously exhibits room-temperature magnetism and optical transparency in the visible spectrum, rendering it a promising candidate for applications in magnetic memory and magneto-optical devices. Traditionally classified as a weak ferromagnet with spin-canting confined to the $ab$ plane, recent investigations have revealed unconventional magnetic phenomena along the $c$ axis. In this work, we identify intricate $c$ axis magnetic behavior in $\mathrm{FeB}{\mathrm{O}}_3$, including anomalous paramagnetic characteristics and evidence of significant magnetic frustration. Temperature- and field-dependent measurements provide quantitative insights into the coercive field and remnant magnetization, key parameters critical for practical applications. Furthermore, we present the first magnetocaloric measurements of $\mathrm{FeB}{\mathrm{O}}_3$, revealing novel features: (1) a distinct magnetic entropy change, (2) detailed characteristics of the antiferromagnetic-to-paramagnetic phase transition at $T_N=347\mathrm{K}$, and (3) evidence of an additional transition at 305 K. Our findings suggest the presence of strong anisotropy in the $\mathrm{FeB}{\mathrm{O}}_3$ system, and the concomitant emergence of multiple magnetic states near $T_N$ upon heating, play a crucial role in these phenomena.

Typical length scales associated with superconductivity are in the range of nanometers. Accordingly, measurements of electrical resistance over much larger distances are supposed to be insensitive to details of spatial inhomogeneities of superconducting order. We observe that current paths adopt a highly nonuniform distribution at the onset of the superconducting transition which is manifested in the development of a finite transverse resistance. The anisotropic distribution of current density indicates the emergence of electronic inhomogeneities perceivable over macroscopic distances, characterized by a length scale which is unrelated to the structural properties of the superconducting films. Our experiments reveal the ubiquitous nature of this phenomenon in conventional superconductors.

Universality and scaling are fundamental concepts in both equilibrium and dynamical phase transitions. Here, we unveil a universal scaling behavior of the critical time of the Loschmidt echo when the system is nonadiabatically driven across the quantum phase transitions. We find that the critical time exhibits a power-law scaling with quenching rate and the scaling exponent is fully determined by the underlining universality class of the equilibrium phase transitions. We explain this unique scaling behavior based on the adiabatic-impulse approximation in the Kibble-Zurek mechanism. This universal scaling behavior is verified to be valid not only in noninteracting single-particle system, but also in many-body interacting system, and not only in the Hermitian system, but also in the non-Hermitian system. Our study unravels a deep and fundamental relationship between dynamical behaviors and equilibrium phase transitions.

${\mathrm{TlYbSe}}_2$ is a new member of the Yb delafossite family, which differs strongly from the previously investigated alkali-metal Yb delafossites. It is characterized by a much larger saturation field (about 20 T) and a higher transition temperature (about 1.8 K) to the field-induced ordered state. As for the other Yb delafossites, long-range magnetic order is absent down to low temperatures at zero field. We report detailed macroscopic and microscopic measurements as a function of magnetic field and temperature to explore the $H-T$ phase diagram of polycrystalline ${\mathrm{TlYbSe}}_2$. Besides bulk methods, such as magnetization and specific heat, spectroscopic methods, such as electron spin resonance (ESR) and nuclear magnetic resonance (NMR), are applied. The magnetic anisotropy can be determined by means of these microscopic probes; in particular, Yb-ESR and Se-NMR are powerful tools here. The magnetization, ESR, and NMR data evidence a large anisotropy factor of about 10 for the ratio of the magnetic moment in the Yb-Se triangular-lattice plane and perpendicular to it. Such a strong spin anisotropy was only found in ${\mathrm{CsYbSe}}_2$, which identifies both systems as prototype two-dimensional triangular-lattice spin liquids. Even though ${\mathrm{CsYbSe}}_2$ shares the same spin anisotropy, it has a much smaller magnetic exchange coupling between the Yb moments than ${\mathrm{TlYbSe}}_2$, which leads to a field-induced ordering at much lower temperatures (1 K) and a smaller saturation field of only 10 T. We speculate that this originates from the use of thallium as a monovalent cation (${\mathrm{Tl}}^{+1}$ with [Xe]$4f^{14}5d^{10}6s^2$) instead of the intensively studied alkali metals (${\mathrm{Na}}^{+1}, {\mathrm{K}}^{+1}, {\mathrm{Rb}}^{+1}, {\mathrm{Cs}}^{+1}$) with completely filled (Ne, Ar, Kr, Xe) shells. In particular, the emergence of a ${\mathrm{Tl}}^{+1}$-based lone-pair $6s^2\text{−}\mathrm{Se}\text{−}4p$ polarization might have a strong impact on the strength and anisotropy of the magnetic exchange among the Yb ions in the ${\mathrm{TlYbSe}}_2$ lattice. In contrast to that, the spin anisotropy of the pseudo-spin-1/2 Yb ions remains unaltered by the presence of Tl $6s^2$ lone pairs.