We investigate the spectral statistics of an interacting fermionic system derived by projecting the Hubbard interaction onto the two lowest-energy, degenerate flat bands of the dice lattice subjected to a $\pi$-flux. Surprisingly, the distributions of level spacings and gap ratios correspond to distinct Gaussian ensembles, depending on the parity of the particle number. For an even number of particles, the spectra conform to the Gaussian orthogonal ensemble, as expected for a time-reversal-symmetric Hamiltonian. In stark contrast, the odd-parity sector exhibits exact double degeneracy of all eigenstates even after resolving all known symmetries, and the Gaussian unitary ensemble accurately describes the spacing distribution between these doublets. The simultaneous emergence of two different random-matrix ensembles within a single physical system constitutes an unprecedented finding, opening new avenues for both random matrix theory and flat-band physics.

We study the spin transport properties of some disordered spin chains with a special focus on the distribution of the frequency-dependent spin conductivity. In the cases of interest here, the systems are governed by an effectively infinite disorder at low energies. A hallmark of this behavior is the wide discrepancy between the average and the typical values of some physical quantities, which are described by extremely broad distributions. We show that such is also the case of the spin conductivity, whose average value is metallic but whose typical one, the physically relevant quantity, is insulating. This solves the apparent contradiction between the prediction of a spin metallic phase of the spin-1/2 disordered XX chain and its known localized behavior (after a mapping to free fermions). Our results are based on analytical and numerical implementations of a strong-disorder renormalization group as well as exact diagonalization studies. We present our analyses in very general terms, valid for systems of any spin $S$ value, but the cases of $S=1/2$ and 1 are studied in greater detail.

The quantum Mpemba effect refers to the anomalous relaxation of a quantum state that, despite being initially farther from the steady state, relaxes faster than a closer counterpart. Detecting such a quantum Mpemba effect typically requires full knowledge of the quantum state during its time evolution, which is an experimentally challenging task since state tomography becomes exponentially difficult as system size increases. This poses a significant obstacle in studying Mpemba effect in complex many-body systems. In this work, we demonstrate that this limitation can be overcome by identifying suitable observables that signal rapid relaxation. Moreover, as long as the system equilibrates to a known unique steady state, it is possible to fully detect the occurrence of quantum Mpemba effect just by measuring the observable for known state preparations. Our approach thus significantly reduces experimental complexity and offers a practical route for observing the quantum Mpemba effect in complex and extended multiqubit setups.

Ytterbium (Yb) metal is unusual among the lanthanide elements in being divalent at ambient conditions, rather than trivalent, which gives it a distinct high-pressure phase transition sequence from that of other lanthanides. Here we describe an x-ray diffraction study of Yb up to 293 GPa to investigate the structure and compressibility of the $hP3$ phase, which we find to be stable up to the highest pressure. We subsequently calculate a further phase transition to the orthorhombic $oF8$ phase above $\sim 330\mathrm{GPa}$, in line with transitions seen in Nd and Sm. Our results underpin future studies of Yb compounds under pressure, in particular the synthesis of ${\mathrm{YbH}}_x$ polyhydrides, for which an accurate understanding of the structure and compressibility of elemental Yb is indispensable.

Anomalous semiconductorlike transport induced by the Curie transition in a $\mathrm{C}{\mathrm{o}}_{51}{\mathrm{V}}_{31}\mathrm{G}{\mathrm{a}}_{18}$ metamagnetic Heusler alloy is evidenced through a combination of experimental and theoretical investigations. The studied alloy crystallizes in $L{2}_1$ cubic austenite at room temperature and transforms into $D{0}_{22}$ tetragonal martensite during cooling, accompanied by an abrupt change of magnetization. Under ambient pressure, a distinct negative temperature coefficient of resistance is observed within the Curie transition region. With increasing hydrostatic pressure, this anomaly is progressively suppressed and eventually vanishes when the martensitic transformation occurs above the Curie temperature ($T_{\mathrm{C}}$). Combined with Hall resistivity measurements, fitting the anomalous segment of the resistivity data reveals an extremely small activation energy ($\mathrm{\Delta }{E}_{\mathrm{g}}$) of $\sim 11.98\pm (0.135$) meV, suggesting a thermal activation process close to $T_{\mathrm{C}}$. Moreover, first-principles calculations identify a narrow band gap in the minority spin channel at the high-symmetry $X$ point, formed between the conduction and valence bands with contributions from V-$e_{\mathrm{g}}$ and Co-$t_{2\mathrm{g}}$ orbitals, respectively, near the Fermi level ($E_{\mathrm{F}}$). The observation of a purely positive linear magnetoresistance, occurring exclusively within the temperature range from $T_{\mathrm{C}}$ to 190 K, further corroborates this unique electronic band structure. This confirms that the Curie transition directly induces the formation of a narrow band gap, which in turn gives rise to the observed anomalous semiconductorlike transport in the studied alloy.

Dimerized valence bond solids appear naturally in spin-1/2 systems on bipartite lattices, with the geometric frustrations playing a key role both in their stability and the eventual melting due to quantum fluctuations. Here, we ask the question of the stability of such dimerized solids in spin-1 systems, taking the anisotropic square lattice with bilinear and biquadratic spin-spin interactions as a paradigmatic model. The lattice can be viewed as a set of coupled spin-1 chains, which in the limit of vanishing interchain coupling are known to possess a stable dimer phase. We study this model using the density matrix renormalization group (DMRG) and infinite projected entangled-pair states (iPEPS) techniques, supplemented by the analytical mean-field and linear flavor-wave theory calculations. While the latter predicts the dimer phase to remain stable up to a reasonably large interchain-to-intrachain coupling ratio $r\lesssim 0.6$, the DMRG and iPEPS find that the dimer solid melts for much weaker interchain coupling not exceeding $r\lesssim 0.15$. We find the transition into a magnetically ordered state to be first order, manifested by a hysteresis and order parameter jump, precluding the deconfined quantum critical scenario. The apparent lack of stability of dimerized phases in 2D spin-1 systems is indicative of strong quantum fluctuations that melt the dimer solid.

Two-dimensional many-body quantum systems can exhibit topological order and support collective excitations with anyonic statistics different from the usual fermionic or bosonic ones. With the emergence of these exotic point-like particles, it is natural to ask what phases can arise in interacting many-anyon systems. To study this topic, we consider the particular case of Fibonacci anyons subject to an anyonic tight-binding model with nearest-neighbor repulsion on a two-leg ladder. Focusing on the case of half-filling, for low interaction strengths an “anyonic” metal is found, whereas for strong repulsion, the anyons form an insulating charge-density wave. Within the latter regime, we introduce an effective one-dimensional model up to sixth order in perturbation theory arising from anyonic superexchange processes. We numerically identify four distinct phases of the effective model, which we characterize using matrix product state methods. These include both the ferro- and antiferromagnetic golden chain phases, as well as phases with ${\mathbb{Z}}_2$ and incommensurate correlations.

Conflicting reports exist on the ground state of the intermetallic compound ${\mathrm{CeRhSn}}_2$. This can be rooted in the sawtoothlike arrangement of two inequivalent Ce sites in the unit cell, which suggests potential geometric magnetic frustration. To resolve these conflicting reports, we conducted a comprehensive study on high-quality single crystals of ${\mathrm{CeRhSn}}_2$ by means of magnetization ($M$), specific heat ($C_{\mathrm{p}}/T$), and resistivity ($\rho$). The system exhibits strong magnetic anisotropy, confirming the $b$ axis as the easy magnetic axis. We establish three successive transitions: an antiferromagnetic order at $T_{\mathrm{N}}=3.65\text{K}$, a first-order ferromagnetic (FM) order at $T_{\mathrm{C}}=1.7\text{K}$ and final transition, at $T=1.5\text{K}$. The transition temperatures are highly field-directional dependent: in a magnetic field, the lowest transition is immediately suppressed while $\mathbf{H}\parallel b$ rapidly merges $T_{\mathrm{C}}$ and $T_{\mathrm{N}}$ into a single second-order transition. Conversely, $\mathbf{H}\parallel c$ suppresses the FM order and reduces $T_{\text{N}}$. Additional ab initio calculations affirm the FM ground state of ${\mathrm{CeRhSn}}_2$. The observation of an enhancement of the Sommerfeld coefficient ($\gamma =76.5\text{mJ/mol}{\text{K}}^2$) may arise from geometric frustration, but it is most consistently attributed to weak Kondo hybridization as frustration cannot be conclusively established through our data.

Recent experiments on few-layer graphene structures have reported indirect signatures of anomalous Hall crystals (AHCs) but the need for a top gate to stabilize the phase precludes direct imaging of the emergent electronic lattice. This situation necessitates the investigation of alternative signatures of AHCs. The gapless phonons of the emergent electronic lattice provide a clear distinction from conventional quantum Hall states, but it may be difficult to disentangle these phonons from the plethora of other possible low-lying modes. Intriguingly, the quantum geometry of the underlying electronic ground state can imprint on the collective modes, possibly leading the phonons themselves to be topological. Were this the case, the resulting neutral chiral edge modes would provide a further signature of an AHC. Using time-dependent Hartree-Fock, we compute the spectra of collective modes of Wigner crystals (WCs) and AHCs arising in minimal models and study the topology of the phonons and low-lying excitons. Across the WC-to-AHC transition, we observe a series of band inversions among collective modes, producing topological phonons and excitons, and a sharp sign change in the phonon Chern number upon entering the AHC phase. We conclude by discussing the relevance of collective-mode topology to experiments on candidate systems for AHCs.

Symmetry-protected topological (SPT) phases in interacting bosonic systems have been widely explored, with many realizations emerging from the interplay of interactions, lattice geometry, and occupancy constraints. Here we investigate a dimerized bosonic lattice model with a local parity coupling and demonstrate that it supports a rich phase diagram containing topological phases at various fillings. Using density matrix renormalization group simulations, we identify two distinct topological regimes absent in the purely dimerized limit: an SPT phase at half filling stabilized by positive parity coupling and a paired-boson topological phase at unit filling, stabilized by negative parity coupling. While the latter is adiabatically connected to a trivial phase and is not symmetry protected in the conventional sense, it exhibits nontrivial topological signatures associated with paired bosons in the constrained Hilbert space. Our results establish local parity coupling as a useful framework for understanding and characterizing topological phases in one-dimensional bosonic systems.

We model $p$-state Fock parafermions on a lattice in one dimension (with occupation per orbital of $0,1,...,p-1$). For $p$ a composite number, they may be mapped to $q_m$-state parafermions where $q_m$ are the prime factors of $p$. For a Hamiltonian with a single-particle spectrum, the parafermions decompose into $q_m$-state parafermions. When $p$ is a power of two, the decomposition is into fermions. We use this to construct a parafermionic Hamiltonian for $p=4$ with a single-particle spectrum using a fermionic tight-binding model which is bilinear in creation and annihilation operators. The single-particle levels may be determined by diagonalizing a square matrix whose order scales linearly with system size, and they are the same as those of the fermionic model. We show that the intermediate statistics of the thermodynamic distribution function for the occupation numbers (known as Gentile statistics) are consistent with the mapping to fermions, and we provide an example calculation of the internal energy and heat capacity for a simple linear chain.

This work presents experimental results on nuclear spin-lattice relaxation times in manganese-doped bulk gallium arsenide (GaAs:Mn), investigated using polarized photoluminescence measurements in an external oblique magnetic field. The experimental data reveal that the nuclear spin system relaxation in the absence of optical pumping is characterized by two distinct timescales: a fast component on the order of milliseconds and a slow component on the order of tens of milliseconds. Increasing the external magnetic field leads to longer spin relaxation times. Our analysis demonstrates that the dominant relaxation mechanism arises from quadrupole interactions induced by fluctuating electric fields during the phonon-assisted tunneling of holes between acceptor sites.

Understanding ballistic phonon transport at the nanoscale is critical for heat management in modern electronic and photonic devices. While semiclassical Boltzmann transport equations (BTE) successfully describe bulk properties, they often neglect phase coherence, which becomes dominant in heterogeneous nanostructures. In this work, we present a real-space derivation of the Wigner transport equation (WTE) based on a power series expansion of a real-space generator. Starting from a tight-binding-like representation of lattice dynamics, our approach enables the systematic inclusion of phonon coherences through off-diagonal density-matrix elements directly in the spatial domain. Unlike existing formulations limited to homogeneous systems, the proposed framework naturally accounts for coherence-induced phenomena, such as phonon reflections at material interfaces. Benchmarks against full-band BTE models demonstrate that this method accurately reproduces semiclassical limits while providing a physically transparent and computationally flexible bridge between lattice-scale interactions and coherent phase-space transport in heterogeneous material systems.

Theoretical studies of semiconductors and band insulators are usually based on variants of the $GW$ method without full self-consistency, such as single-shot $G^0{W}^0$ or quasiparticle self-consistent $GW$. Fully self-consistent $GW$ provides a poor description of the gap size and electronic structure due to the lack of vertex corrections. While it is hard to predict at which order corrections can be neglected, local vertex corrections to all orders can be consistently included by combining $GW$ with extended dynamical mean field theory (EDMFT). Here, we show that ab initio multitier $GW+\mathrm{EDMFT}$ calculations, which achieve full self-consistency in a suitably defined low-energy space, provide an accurate description of semiconductors and band insulators, comparable to the established methods which are typically used for this class of materials. Our results demonstrate that the range of applicability of $GW+\mathrm{EDMFT}$ extends to weakly correlated systems, and they imply that despite the weak correlations, local vertex corrections are an important ingredient in the diagrammatic treatment of semiconductors and band insulators.