Photonic lattices facilitate band structure engineering, supporting both localized and extended modes through their geometric design. However, greater control over these modes can be achieved by taking advantage of the interference effect between external drives with precisely tuned phases and photonic modes within the lattice. In this work, we build on this principle to demonstrate optical switching, directed light propagation, and site-specific localization in a one-dimensional photonic lattice of coupled microresonators by resonantly driving the system with a coherent field of controlled phase. Importantly, our experimental results provide direct evidence that increased driving power acts as a tuning parameter enabling nonlinear localization at frequencies previously inaccessible in the linear regime. These findings open different avenues for controlling light propagation and localization in lattices with more elaborate band structures.

In the last decades, multifaceted manifestations of the breakdown of the self-consistent perturbation theory have been identified for the many-electron problem. Yet, the investigations have been so far mostly limited to paramagnetic states, where symmetry breaking is not allowed. Here, we extend the analysis to the spontaneously symmetry-broken antiferromagnetic (AF) phase of the repulsive Hubbard model. To this aim, we calculated two-particle quantities using dynamical mean-field theory for the AF-ordered Hubbard model and studied the possible occurrence of divergences of the irreducible vertex functions in the charge and spin sectors. Our calculations pinpoint the divergences in the AF phase diagram, showing that while the onset of AF order mitigates the breakdown of the perturbation expansion, it does not fully prevent it. Moreover, we have been able to link the changes in the dynamical structure of the corresponding generalized susceptibilities to the physical crossover from a weak-coupling (Slater) to a strong-coupling (Heisenberg) antiferromagnet, which takes place as the interaction strength is gradually increased. Finally, we discuss possible physical consequences of the irreducible vertex divergences in triggering phase-separation instabilities within the AF phase and elaborate on the implications of our findings for two-dimensional systems, where the onset of a long-range AF order is prevented by the Mermin-Wagner theorem.

The prospect of transforming a Dirac topological semimetal (TSM) into a Weyl TSM phase, following doping by magnetic impurities, is central to TSM applications. The magnetic field from polarized $d$ levels of magnetic impurities produces a field with a sharp local structure. To what extent magnetic impurities act in the same manner as an applied field and what are the effects of such a field on the electronic structure of a Dirac TSM are the subject of this paper. We present electronic structure calculations of bulk ${\mathrm{Cd}}_3{\mathrm{As}}_2$ with substitutional doping of Mn impurities in the dilute alloy range. Quasiparticle $GW$ ($\mathrm{QS}GW$) ab initio electronic structure calculations are used in conjunction with $k·p$ model Hamiltonian calculations. As expected, we observe the splitting of the Dirac points into pairs of Weyl points following the doping with Mn. We also show that the electronic structure of Mn-doped ${\mathrm{Cd}}_3{\mathrm{As}}_2$ can be emulated by the electronic structure of pristine ${\mathrm{Cd}}_3{\mathrm{As}}_2$ with an appropriate external magnetic field. Some properties of the conductivity of bulk ${\mathrm{Cd}}_3{\mathrm{As}}_2$ for different magnetic field orientations are also investigated. Our results inform future opportunities for unique device functionality based on band structure tuning not found in conventional magnetic Weyl TSM.

We obtain a closed-form expression for the energy spectrum of $\mathcal{P}\mathcal{T}\text{-symmetric}$ superlattice systems with complex potentials of periodic sets of two $\delta \mathrm{potentials}$ in the elementary cell. In the presence of periodic gain and loss, we analyzed in detail a diatomic crystal model, varying either the scatterer distances or the potential heights. It is shown that at a certain critical value of the imaginary part of the complex amplitude, topological states depending on the lattice size and the configuration of the unit cell can be pushed out from the given region. This may happen at the $\mathcal{PT}\text{-symmetry}$ breaking (exceptional) points.

Chiral superfluid ${}^3\mathrm{He}\text{−}\mathrm{A}$ contained in narrow-gapped parallel plate cell with in-plane external magnetic field is expected to form uniformly aligned texture of chiral vectors, which denote the direction of Cooper pair angular momentum. In the real experimental situation, we often observe the existence of a few millimeter sized chiral domains and chiral domain walls in between them. A persistent orbital supercurrent is expected to flow along the wall. We have succeeded in tilting chiral domain walls by applying external supercurrent, which interacts with the orbital supercurrent. This observation confirmed the existence of macroscopic orbital supercurrent along the chiral domain wall. The tilting angle depends on the direction and magnitude of the external supercurrent as well as the direction of the chiral vector in adjacent chiral domains. This allowed us to determine the direction of the chiral vector in each chiral domain. The measured tilting angle also suggests that the magnitude of macroscopic angular momentum of each chiral domain is as large as the ground-state angular momentum $\hslash$ times a number of ${}^3\mathrm{He}$ particles divided by 2.

Classical simulation of a programmable quantum processor is crucial in identifying the threshold of a quantum advantage. We demonstrate the simple update of projected entangled-pair states (PEPSs) in the Vidal gauge that represent random quantum circuit states, which center around recent quantum advantage claims. Applied to square lattices of qubits akin to state-of-the-art superconducting processors, the PEPS representation is exact for circuit depths less than ${\mathcal{D}}_{\mathrm{tr}}=\beta {log}_2\chi$, where $\chi$ is the maximum bond dimension and $2\lesssim \beta \lesssim 4$ depends on the choice of two-qubit gates, independent of the qubit number $n$. We find the universal scaling behaviors of the state fidelity by treating large-scale circuits of $n\le {10}^4$, using $\chi \le 128$ on a conventional CPU. Our method has a polynomial scaling of computational costs with $n$ for circuit depth $\mathcal{D}=O(logn)$ and is more advantageous than matrix product state approaches if $n$ is large. This work underscores PEPSs as a scalable tool for benchmarking quantum algorithms with future potential for sampling applications using advanced contraction techniques.

Vanadium-based kagome metal of $\mathrm{Sc}{\mathrm{V}}_6\mathrm{S}{\mathrm{n}}_6$ has been of current interest as it features unique charge density wave (CDW) ordering accompanied by a structural phase transition, indicating the importance of lattice distortion for the onset of CDW order. To unveil the role of each individual atomic site for the phase transition, we employed a local probe through the nuclear magnetic resonance (NMR) measurements in which the NMR signals from ${}^{45}\mathrm{Sc}, {}^{51}\mathrm{V}$, and ${}^{119}\mathrm{Sn}$ nuclei in both normal and CDW states were observed. From the comparison between the quadrupole splitting of ${}^{45}\mathrm{Sc}$ and ${}^{51}\mathrm{V}$ NMR satellite lines, a noticeable increase in the ${}^{45}\mathrm{Sc}$ quadrupole frequency below the transition temperature was identified. The finding can be accounted for by the structural distortion mainly involving the displacement of Sc and Sn atoms along the crystal $c$ axis. From the analysis of the temperature dependences of the NMR shift, we quantitatively obtained the change in the electronic states for each atom associated with the phase transition. In particular, we demonstrated a marked reduction in the V $3d$ density of states at the Femi level, which can be rationalized as a manifestation of the structural transition. Remarkably, we resolved three ${}^{119}\mathrm{Sn}$ NMR resonance lines corresponding to three nonequivalent crystallographic Sn sites and therefore estimated the variation in the $5s$ electronic states of each Sn atom in $\mathrm{Sc}{\mathrm{V}}_6\mathrm{S}{\mathrm{n}}_6$.

We discuss predominant order parameters for structural chirality and demonstrate that time-reversal-even axial quadrupole plays a key role in stabilizing a chiral structure. Using the symmetry-adapted closest Wannier model of the trigonal Te and Se, we quantify the evolution of the spin-independent (spinless) and spin-dependent (spinful) electric toroidal (ET) (axial) multipole moments across the transition from an achiral to a chiral structure. Our results clearly identify that a spin-independent off-diagonal real hopping between $p$ orbitals, which corresponds to the bond-cluster spinless ET quadrupole of $(3z^2-r^2)$ type $G_u$, is the predominant order parameter in stabilizing helical structures. We further elucidate that the above itinerant spinless ET quadrupole induces a monopolelike orbital angular momentum texture in the momentum space, which can be observed via circular dichroism in soft x-ray photoemission spectroscopy measurement. Our findings highlight a critical role of the orbital angular momentum in chiral materials rather than less dominant spin angular momentum arising from the relativistic spin-orbit coupling.

The advent of non-Hermitian physics has enriched the plethora of topological phases to include phenomena without Hermitian counterparts. Despite being among the most well-studied uniquely non-Hermitian features, the topological properties of multifold exceptional points, $n$-fold spectral degeneracies ($\mathrm{EP}n\mathrm{s}$) at which also the corresponding eigenvectors coalesce, were only recently revealed in terms of topological resultant winding numbers and concomitant Abelian doubling theorems. Nevertheless, a more mathematically fundamental description of $\mathrm{EP}n\mathrm{s}$ and their topological nature has remained an open question. To fill this void, in this article, we revisit the topological classification of $\mathrm{EP}n\mathrm{s}$ in generic systems and systems with local symmetries, generalize it in terms of more mathematically tractable (local) similarity relations, and extend it to include all such similarities as well as nonlocal symmetries. Through the resultant vector, whose components are given in terms of the resultants between the corresponding characteristic polynomial and its derivatives, the topological nature of the resultant winding number is understood in several ways: in terms of (1) the tenfold classification of (Hermitian) topological matter, (2) the framework of Mayer-Vietoris sequence, and (3) the classification of vector bundles. The classification scheme further predicts the existence of topological bulk Fermi arcs protected by a ${\mathbb{Z}}_2$-invariant, induced by nonlocal symmetries, dubbed ${\mathbb{Z}}_2$-protected Fermi arcs. Our work reveals the mathematical foundations on which the topological nature of $\mathrm{EP}n\mathrm{s}$ resides, enriches the theoretical understanding of non-Hermitian spectral features, and will therefore find great use in modern experiments within both classical and quantum physics.

A theoretical approach to estimating stable drainage front widths in three-dimensional (3D) random porous media under gravitational and capillary effects is presented here. Based on the frontier of the infinite cluster in gradient percolation, we propose an expression for the 3D front width dependent on the pore-network topology, the distribution of capillary-pressure thresholds for the pore throats, the stabilizing capillary-pressure gradient, the average pore size, and the correlation length critical exponent from percolation in three dimensions. Theoretical predictions are successfully compared to numerical results obtained with a bond invasion-percolation model for a wide range of drainage flow parameters.

We present a theoretical study of a mesoscopic two-dimensional electron gas confined in a double quantum well that is coupled to a uniform quasistatic cavity mode via fluctuations of the dipole moment. We focus on the regime of large number of electrons participating in the virtual intersubband transitions. In this regime, the effective photonic potential is no longer quadratic but, instead, it contains large number of minima. Each minimum represents a nearly harmonic oscillator with the renormalized cavity frequency that is much greater than its bare value. The energy offset of a minimum scales quadratically with respect to the photon coordinate corresponding to this minimum. These energy offsets determine the statistical weight of each minimum, and altogether they result in the additive correction to the heat capacity of the system. This correction exhibits a Schottky anomaly and a $0.5k_{\text{B}}$ plateau at low temperatures. This behavior can be associated with the emergence of a new degree of freedom. This degree of freedom does not manifest in the optical conductivity and can only be observed via the heat capacity measurement.

Flat bands in twisted materials have attracted considerable attention due to the emergence of correlated phases that can be associated with the non-Wannier-representable nature of its single-particle states. Specifically, these bands can exhibit a class of topology that can be nullified by the addition of trivial bands, termed fragile topology, which has required an expansion of prior classification schemes. However, existing approaches for predicting fragile topology rely on momentum-space methods, e.g., Wilson loops, presenting a fundamental challenge for using fragile topology as a predictor of correlated phases in aperiodic systems, such as incommensurate twist angles in moiré materials. Here, we develop a ${\mathbb{Z}}_2$ energy-resolved topological marker for classifying fragile phases using a system’s position-space description, enabling the direct classification of finite, disordered, and aperiodic materials. By translating the physical symmetries protecting the system’s fragile topological phase into matrix symmetries of the system’s Hamiltonian and position operators, we use matrix homotopy to construct our topological marker while simultaneously yielding a quantitative measure of topological robustness. We demonstrate our framework’s effectiveness in both a low-energy tight-binding model and a continuum photonic crystal model of $C_2\mathcal{T}$-symmetric systems, and find that fragile topology can both persist under strong disorder and even exhibit disorder-induced reentrant phase transitions. Our photonic crystal results also demonstrate the robustness of fragile topology, and the applicability of our approach, to heterostructures lacking a bulk spectral gap. Overall, our framework serves as an efficient tool for elucidating fragile topology, offering guidance for the prediction and discovery of correlated phases in both crystalline and aperiodic materials.

We explore a two-dimensional Hubbard model adapted to host altermagnetic states. Utilizing Hartree-Fock (HF) and dynamical mean-field theory (DMFT), we uncover that the magnetic solutions of this model feature Dirac points in their spectrum. HF predicts a gap opening at a critical interaction strength, a result corroborated by DMFT calculations at zero temperature. However, at finite temperature and high interaction strengths, Dirac points re-emerge at high energies in the spectral function, even if they are absent in the noninteracting and HF-predicted band structures. Analytical arguments reveal that this phenomenon arises near Mott insulating solutions from the frequency dependence of the self-energy, a behavior not captured by static mean-field theory. We identify distinctive dynamical signatures of correlated altermagnetic states in the spin-resolved optical conductivity, notably a double-peak structure likely linked to high-energy Dirac conelike bands. Moreover, the spin-resolved response exhibits spin-selective activation at different photon energies, pointing to potential applications in spin-dependent optical control. We also propose perturbations to the model that can induce a topological gap in the spectrum, leading to a transition from topologically trivial to nontrivial states by varying doping, interaction strength, and temperature.

We develop a theory of heat transport in nonchiral transmission lines (TLs) of quantum Hall edge channels coupled to Ohmic contacts that accounts for a dynamical accumulation of charge in the reservoirs. As a consequence, heat transport is driven by charge fluctuations in the heat Coulomb blockade regime. This framework challenges conventional paradigms by revealing a giant heat flux effect—a significant amplification in heat transport arising from nontrivial fluctuation-dissipation relations. Through a Langevin-based approach, we derive the effective noise power in the chiral currents, which underlies this enhanced heat flux. Our findings predict clear experimental signatures unique to nonchiral TLs, as well as provide insights into finite-frequency effects, showing crossovers to more conventional diffusive behavior. This work offers a perspective on feedback mechanisms in quasi-one-dimensional heat transport with implications for dissipation control in low-dimensional quantum systems.

We propose a method for converting single microwave photons to single optical sideband photons based on spinful impurities in magnetic materials. This hybrid system is advantageous over previous proposals because (i) the implementation allows much higher transduction rates (${10}^3$ times faster at the same optical pump Rabi frequency) than state-of-the-art devices, (ii) high-efficiency transduction is found to happen in a significantly larger space of device parameters (in particular, over $1\text{GHz}$ microwave detuning), and (iii) it does not require mode volume matching between optical and microwave resonators. We identify the needed magnetic interactions as well as potential materials systems to enable this speed up using erbium dopants for telecom compatibility. This is an important step towards realizing high-fidelity entangling operations between remote qubits and will provide additional control of the transduction through perturbation of the magnet.