Interacting fermionic chains exhibit extended regions of topological degeneracy of their ground states as a result of the presence of Majorana or parafermionic zero modes localized at the edges. In the opposite limit of infinite temperature, the corresponding nonintegrable spin chains, obtained via generalized Jordan-Wigner mapping, are known to host so-called almost strong zero modes, which are long-lived with respect to any bulk excitations. Here we study the fairly unexplored territory that bridges these two extreme cases of zero and infinite temperature. We blend two established techniques for states, the Lanczos series expansion and a tensor network ansatz, uplifting them to the level of operator algebra. This allows us to efficiently simulate large system sizes for arbitrarily long timescales and to extract the temperature-dependent decay rates. We observe that for the Kitaev-Hubbard model, the decay rate of the edge mode depends exponentially on the inverse temperature $\beta$, and on an effective energy scale ${\mathrm{\Delta }}_{\mathrm{eff}}$ that is greater than the thermodynamic gap of the system $\mathrm{\Delta }$.

Quantum magnonics based on yttrium iron garnet (YIG) spheres provides a new arena for observing macroscopic quantum states. Here, we propose to prepare two kinds of non-Gaussian magnonic states by adding a single magnon to two Gaussian states, namely, coherent and thermal states. We adopt an optomagnonic system of a YIG sphere and use fast optical pulses to weakly activate the magnon-induced Stokes scattering. Conditioned on the detection of a polarized single photon, a single magnon can be added to an initial Gaussian state. We use a microwave cavity to prepare an initial magnon coherent state and finally read out the generated single-magnon added coherent or thermal state. Both the non-Gaussian states of a magnon mode in a large YIG sphere are macroscopic quantum states, which exhibit many nonclassical properties, such as sub-Poissonian statistics, quadrature squeezing, and a negative Wigner function. Further, both states show a smooth transition from a quantum state to a classical state with the change of the coherent or thermal magnon excitations and thus can be used for the fundamental study of the quantum-to-classical transition.

Quasiperiodic potentials and dipolar interactions each impose long-range order in quantum systems, but their interplay unlocks a rich landscape of unexplored quantum phases. In this work, we investigate how dipolar bosonic crystals respond to correlated disorder in the form of quasiperiodic potentials. Using exact numerical simulations and a suite of observables—including order parameters, energy, density distributions, and two-body coherence measures—we explore one-dimensional dipolar bosons in quasiperiodic lattices at both commensurate and incommensurate fillings. Our results reveal a complex competition between superfluid, Mott-insulator, density-wave, and crystalline phases, governed by the intricate balance of dipolar interactions, kinetic energy, and disorder strength. Crucially, we identify mechanisms that influence dipolar crystals, showing their surprising robustness even in the presence of strong quasiperiodic disorder. Strikingly, we challenge previous claims by demonstrating that a kinetic crystal phase—expected to precede full crystallization—does not emerge in the ground state. Instead, its traits appear only under moderate disorder, but never fully develop, giving way to a direct transition from a charge density wave to a crystal state. These findings provide new insights into the resilience of many-body quantum phases in complex environments and pave the way for engineering exotic quantum states in ultracold atomic systems.

The anomalous bulk-boundary correspondence in non-Hermitian systems featuring an intricate interplay between skin and boundary modes has attracted enormous theoretical and experimental attention. Still, in dimensions higher than one, this interplay remains much less understood. Here we provide insights from exact analytical solutions of a large class of models in any dimension $d$, with open boundaries in $d_c\le d$ directions, and by tracking their topological origin. Specifically, we show that amoeba theory accounting for the separation gaps of the bulk modes augmented with higher-dimensional generalizations of the biorthogonal polarization and the generalized Brillouin zone approaches accounting for the surface gaps of boundary modes provide a comprehensive understanding of these systems.

The well-known and celebrated first-primer classical analysis of a one-dimensional inversion-asymmetric assembly of electric point charges interconnected by mechanical springs shows that the system is piezoelectric and characterized by a parameter-dependent but constant piezoelectric coefficient $d$ defined as the ratio between the change in system length and the change in electric field. The former system is the simplest system displaying the phenomenon of piezoelectricity. We demonstrate that a quantum-mechanical analysis of the Hamiltonian for the same system of electric point charges and mechanical springs leads to a piezoelectric constant that depends not only on the system parameters but also on the eigenstate. Hence, the piezoelectric constant, determined as the ratio between the change in the expectation value of the system length and the change in the applied electric field, is quantized. It is demonstrated analytically and numerically, which is a necessary condition, that the quantized piezoelectric constant vanishes if the system Hamiltonian is inversion symmetric.

Van der Waals (vdW) layered magnetic materials have attracted much attention from the physics and materials science communities. Here we successfully obtained a monoclinic vdW ferromagnet $\mathrm{NbFeT}{\mathrm{e}}_2$ by high-temperature growth, and systematically characterized its magnetic, electrical, and magnetotransport properties. When temperature $T<53$ K (Curie temperature), $\mathrm{NbFeT}{\mathrm{e}}_2$ exhibits metamagnetism: the ferromagnetism under high magnetic fields ($H>0.7$ T) and spin-glass-like behavior at low magnetic fields ($H<0.7$ T), respectively. Analysis of temperature-dependent resistivity reveals the influence of Mott variable range hopping and magnon scattering below the Curie temperature. Based on the first-principles electronic band structure, the Mott variable range hopping is related to the pseudogaplike density of states and ferrimagnetism in $\mathrm{NbFeT}{\mathrm{e}}_2$. Notably, there are also both anomalous Hall effect and topological Hall effect observed in $\mathrm{NbFeT}{\mathrm{e}}_2$ below the Curie temperature, which correlates to the ferromagnetism and chiral-spin-glass behavior, respectively. In particular, the topological Hall effect is attributed to the finite scalar spin chirality of slightly canted Fe spin clusters in $\mathrm{NbFeT}{\mathrm{e}}_2$ with Nb deficiency. This work demonstrates that the magnetic and magnetotransport properties of $\mathrm{NbFeT}{\mathrm{e}}_2$ crystals are strongly dependent on the stoichiometry, delicate competition between exchange interactions, and spin-orbit coupling in quasi-two-dimensional crystal structure.

We theoretically discover possible dc-current induction and high-harmonic generation from photodriven chiral fermions in B20-type semimetals irradiated with circularly polarized light as nonlinear optical responses with several unconventional properties. First, we find multiple sign changes of the induced bulk dc photocurrent as a function of light parameters, which is ascribed to the nature of asymmetric photon-dressed bands in chiral systems. Moreover, we observe a parity-dependent directivity of high-harmonic generation where the odd- and even-order harmonics have intensities only in directions perpendicular and parallel to the polarization plane, respectively, which can be understood from dynamical symmetry of the present photodriven chiral systems.

We study the non-Fermi-liquid state formed by an isotropic, degenerate Fermi gas in two spatial dimensions interacting with a U(1) gauge field. Our calculation uses the functional renormalization group (fRG) with a soft frequency cutoff for the fermions. The fRG scheme we employ takes account of the gauge symmetry, which imposes relations (modified Ward-Takahashi identities) between the couplings which constrain the RG flow. The critical exponents and couplings we find for the resulting non-Fermi liquid are mostly insensitive to whether we enforce the gauge symmetry constraints, which signifies either that the constraints are superfluous or that the frequency-cutoff scheme is particularly robust. The exception is the gauge-boson mass term, which is RG-relevant about the fixed point without the constraints but is irrelevant when they are enforced. The latter is physically accurate, as a gauge symmetry cannot be spontaneously broken. In addition, we find $z=2$ and $\mathrm{\Sigma }(\omega ,k_F)\sim {\omega }^{1/2}$ for the boson dynamical exponent and scaling of the fermion self-energy, respectively. These results differ considerably from those of past works on the model, though we argue for their plausibility.

When a quantum emitter (QE) is placed in close proximity to a plasmonic metal nanoparticle within an external optical field, a dipole-dipole coupling arises, resulting in a highly tunable hybrid nanosystem that surpasses the optical manipulation capabilities of the individual components. These hybrid systems enable the exploration and manipulation of optical fields at the intersection between classical and quantum phenomena. Theoretical models of this interaction have typically been limited to the extreme orientations, where the QE and plasmonic dipoles are polarized either along or perpendicular to the interparticle axis, for analytical tractability. In this work, we generalize the semiclassical optical dipole-dipole interaction model for a two-level quantum emitter in a plasmonic field for arbitrary polarization angles. We show that the total field experienced by the quantum emitter at intermediate angles does not necessarily align with the external input field and discuss the implications of varying the polarization angle of the external input field.

We investigate a dilute Bose gas with both a short-range contact and an effective long-range interaction between the atoms. The latter is induced by the strong coupling to a cavity light mode and is spatially characterized by a periodic signature and a tunable envelope rooted in the pumping of the cavity. We formulate a Bogoliubov theory based on a homogeneous mean-field description and quantum fluctuations around it. The competition between the repulsive contact interaction and the long-range interaction allows the formation of self-bound quantum droplets. This generic approach is applied to two cavity setups, one without and one with a momentum-conserving effective long-range interaction between the atoms in the form of a driven dispersive cavity mode and a multimode cavity, respectively. For both cases we show analytically how the size and the central density of the cavity-induced quantum droplets depend on the contact interaction strength and on the shape of the spatial envelope of the long-range interaction.

Realizing Kitaev interactions on triangular lattices offers a compelling platform for exploring quantum spin liquid physics beyond the conventional honeycomb-lattice framework. Here, we investigate the triangular-lattice antiferromagnet ${\mathrm{KCeSe}}_2$, where multiple probes reveal strong magnetic anisotropy, suggesting significant Kitaev physics. Through detailed and combined analysis of magnetization, neutron scattering, and thermodynamic experiments, we identify dominant ferromagnetic Kitaev $(K=-1.82\mathrm{K})$ and antiferromagnetic Heisenberg $(J=1.34\mathrm{K})$ interactions that stabilize a stripe-$yz$ ordered ground state via an order-by-disorder mechanism. Magnetic fields applied along the Kitaev bond direction induce two phase transitions at 1.67 and 3.8 T, consistent with density matrix renormalization group calculation predictions of a progression from stripe-$yz$ to stripe-canted and spin-polarized phases. Near the 1.67 T quantum critical point, enhanced quantum fluctuations suggest conditions favorable for exotic excitations. These results establish ${\mathrm{KCeSe}}_2$ as a platform for exploring Kitaev physics on triangular lattices.

We study a cylindrical plasmonic waveguide consisting of a magnetic Weyl semimetal embedded in a dielectric medium. We determine the dispersion relation of the surface plasmon polaritons and show how it depends on the plasma frequency, the radius of the semimetal core, and the separation between the nodes. We show that the band structure, which modifies the electrodynamics in the medium, manifests itself through a pronounced asymmetry in the dispersion curves and a giant splitting in the group velocity, with the orbital angular momentum as a control parameter for the direction of propagation.

We describe our implementation of fermionic tensor network contraction on arbitrary lattices within both a globally ordered and a locally ordered formalism. We provide a pedagogical description of these two conventions as implemented for the quimb library. Using hyperoptimized approximate contraction strategies, we present benchmark fermionic projected entangled pair state simulations of finite Hubbard models defined on the three-dimensional diamond lattice and random regular graphs.