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arXiv2018

Magnetic anisotropy in HoIr$_2$Si$_2$ ($I4/mmm$)

Single crystals of HoIr$_2$Si$_2$ with the body-centered ThCr$_2$Si$_2$-type structure ($I4/mmm$) were grown by Bridgman method from indium flux. Single crystal structure determination yielded a Si-z position of 0.378(1) in the structure. We excluded the presence of the high temperature phase with the primitive CaBe$_2$Ge$_2$-type structure ($P 4/n m m$) by powder X-ray diffraction. Magnetic measurements on the single crystals yield a Neel temperature of $T_{\rm N}=22\,\rm K$. In the inverse magnetic susceptibility a strong anisotropy with Weiss temperatures $Θ_{W}^{001}=26\,\rm K$ and $Θ_{W}^{100}=-26\,\rm K$ occurs above $T_{\rm N}$. The effective magnetic moment $μ_{\rm eff}^{001}=10.64μ_{B}$ and $μ_{\rm eff}^{100}=10.53μ_{B}$ is close to the expected value for a free Ho$^{3+}$ ion, $μ_{\rm eff}^{calc}=10.6μ_{B}$. The field dependent magnetization shows a step-like behaviour due to crystalline electric field effects.

cond-mat.str-el↗

arXiv2018

Effect of disorder on the quantum spin liquid candidate Na$_4$Ir$_3$O$_8$

We report on the effects of introducing magnetic and non-magnetic disorder in the hyperkagome iridate quantum spin liquid (QSL) candidate Na$_4$Ir$_3$O$_8$ by partially replacing Ir$^{4+}$ ($S = 1/2$) with Ru$^{4+}$ ($S = 1$) or Ti$^{4+}$ ($S = 0$). Specifically, we synthesized Na$_4$(Ir$_{1-x}$Ru$_x$)$_3$O$_8 (x = 0.05, 0.10, 0.2, 0.3)$ and Na$_4$Ir$_{2.7}$Ti$_{0.3}$O$_8$ samples and measured electrical transport, AC and DC magnetization, and heat capacity down to $T = 1.8$ K. Na$_4$Ir$_3$O$_8$ is associated with a large Weiss temperature $θ= -650$ K, a broad anomaly in magnetic heat capacity C$_{mag}$ at T $\approx25$ K, low temperature power-law heat capacity, and spin glass freezing below $T_f \approx 6$ K. We track the change in these characteristic features as Ir is partially substituted by Ru or Ti. We find that for Ru substitution, $θ$ increases and stays negative, the anomaly in C$_{mag}$ is suppressed in magnitude and pushed to lower temperatures, low temperature $C \sim T^α$ with $α$ between $2$ and $3$ and decreasing towards $2$ with increasing $x$, and $T_f$ increases with increase in Ru concentration $x$. For Ti substitution we find that $θ$ and T$_f$ become smaller and the anomaly in $C_{mag}$ is completely suppressed. In addition, introducing non-magnetic Ti leads to the creation of orphan spins which show up in the low temperature magnetic susceptibility.

cond-mat.str-el↗

arXiv2018

Efficient population transfer via non-ergodic extended states in quantum spin glass

We analyze a new computational role of coherent multi-qubit quantum tunneling that gives rise to bands of non-ergodic extended (NEE) quantum states each formed by a superposition of a large number of computational states (deep local minima of the energy landscape) with similar energies. NEE provide a mechanism for population transfer (PT) between computational states and therefore can serve as a new quantum subroutine for quantum search, quantum parallel tempering and reverse annealing optimization algorithms. We study PT in a quantum n-spin system subject to a transverse field where the energy function $E(z)$ encodes a classical optimization problem over the set of spin configurations $z$. Given an initial spin configuration with low energy, PT protocol searches for other bitstrings at energies within a narrow window around the initial one. We provide an analytical solution for PT in a simple yet nontrivial model: $M$ randomly chosen marked bit-strings are assigned energies $E(z)$ within a narrow strip $[-n -W/2, n + W/2]$, while the rest of the states are assigned energy 0. We find that the scaling of a typical PT runtime with n and L is the same as that in the multi-target Grover's quantum search algorithm, except for a factor that is equal to $\exp(n /(2B^2))$ for finite transverse field $B\gg1$. Unlike the Hamiltonians used in analog quantum unstructured search algorithms known so far, the model we consider is non-integrable and population transfer is not exponentially sensitive in n to the weight of the driver Hamiltonian. We study numerically the PT subroutine as a part of quantum parallel tempering algorithm for a number of examples of binary optimization problems on fully connected graphs.

quant-ph↗

arXiv2018

High Field Magneto-Conductivity Analysis of Bi2Se3 Single Crystal

We report the high field (up to 14Tesla) magneto-conductivity analysis of Bi2Se3 topological insulator grown via the self flux method. The detailed experimental investigations including crystal growth as well as the electrical, thermal and spectroscopic characterizations of the resultant Bi2Se3 single crystal are already reported by some of us. The current letter deals with high field magneto-conductivity analysis in terms of Hikami Larkin Nagaoka (HLN) model, which revealed that the electronic conduction is dominated by both surface states driven weak anti localization (WAL), as well the bulk WL (weak localization) states. Further, by applying the HLN equation we have extracted the fitting parameters i.e., phase coherence length and the pre-factor. The HLN equation exhibited values of [pre factor close to -1.0, indicating both WAL and WL contributions. On the other hand, the extracted phase coherence length is seen to decrease from 11.125 nm to 5.576 nm as the temperature is increased from 5K to 200K respectively. Summarily, the short letter discusses primarily the temperature dependent magneto-conductivity analysis of pristine Bi2Se3 single crystal by the HLN model.

cond-mat.mtrl-sci↗

arXiv2018

Quantum continuum fluctuations in glassy perovskite Ca(Co$_{0.15}$Ru$_{0.85}$)O$_{3}$

The quantum spin continuum and classical spin freezing, associated with a glassy state, represent two opposite extremes of a correlated electronic material. Here, we report the coexistence of a quantum spin continuum with a weak spin glass order in Co-doped CaRuO$_{3}$ perovskite near the chemical doping dependent metal-insulator transition boundary. Inelastic neutron measurements on Ca(Co$_{0.15}$Ru$_{0.85}$)O$_{3}$ at low temperature, $T$ = 1.5 K, reveal a continuum spectrum in the $Q-E$ space due to uncorrelated spin fluctuations. This persists across the glass transition at $T_G \simeq$23 K. Furthermore, scaling of the dynamic susceptibility yields a very small scaling coefficient $α$ $\simeq$ 0.1, suggesting extreme locality of the dynamic properties. The experimental results indicate the realization of a narrow regime where the distinction between continuum dynamic behavior and glass-like regimes is reduced.

cond-mat.str-el↗

arXiv2018

Evidence for breathing-type pseudo Jahn-Teller distortions in the charge density wave phase of 1$T$-TiSe$_2$

The charge density wave (CDW) phase in 1$T$-TiSe$_2$ is investigated using angle resolved photoemission spectroscopy (ARPES) and neutron scattering measurements. Our ARPES results reveal a clear temperature dependence of the chemical potential of the system. They also demonstrate specific changes encountered by the Se 4$p$ valence and Ti 3$d$ conduction bands as the temperature of the system is decreased through $T_{\text{CDW}}$. The valence band undergoes a downward shift, whereas the conduction band remains unaffected. The crystal structure in the CDW state shows a distinct split of the Ti-Se atomic correlations that are reminiscent of Jahn-Teller distortions, manifested in a breathing-type mode. The ARPES data together with the local structure analysis support a direct link between Jahn-Teller-like distortions and the CDW order in 1$T$-TiSe$_2$.

cond-mat.str-el↗

arXiv2021

Frustration induced inversion of magnetocaloric effect and enhanced cooling power in substituted Pyrochlore Iridates

We investigate the effect of partial replacement of extended 5d Ir4+ sites by localized 3d Cr3+ moments on the magnetocaloric properties of Y2Ir2O7 (YIO) pyrochlore iridates. We find that Y2Ir2-xCrxO7 (YICO) undergoes cluster glass transition, possibly due to RKKY like interaction between localized Cr3+ moments occupying random sites in the pyrochlore network, mediated by 5d Ir conduction electrons. The coexistence of ferromagnetic and antiferromagnetic clusters give rise to the conventional and inverse magnetocaloric effect (MCE). We observe significant enhancement of conventional as well as inverse MCE with substitution. Although the value of conventional MCE and inverse MCE in substituted Iridates are not large, the effect spans over a giant working temperature window, thus leading to orders of magnitude enhancement of cooling power, the value being comparable to standard magnetocalric materials.

cond-mat.str-el↗

arXiv2022

Structural and magnetic properties of the quasicrystal approximant Au$_{65}$Ga$_{21}$Tb$_{14}$

Magnetic properties of the quasicrystal approximant Au$_{65}$Ga$_{21}$Tb$_{14}$ were investigated by the magnetization and the neutron diffraction experiments. The temperature dependences of the magnetic susceptibility and the magnetization curve indicate dominant ferromagnetic interactions, while the whirling antiferromagnetic order was found from the neutron diffraction experiments. In the antiferromagnetic phase, the magnetic moments are aligned almost perpendicular to a pseudo five-fold symmetry axis, which should correspond to the easy-axis direction of a Tb atom. The magnetic properties similar to those of Au$_{72}$Al$_{14}$Tb$_{14}$ in spite of the difference in the electron-per-atom ratio suggest the robustness of the easy-axis anisotropy against the chemical substitution of the nonmagnetic atoms.

cond-mat.str-el↗

arXiv2022

Magnetic order and spin liquid behavior in [Mo3+]^{11+} triangular magnets

Molecular magnets based on [Mo$_3$]$^{11+}$ units with one unpaired electron per trimer have attracted recent interest due to the identification of quantum spin liquid candidacy in some family members. Here, we present comprehensive measurements on polycrystalline samples of ZnScMo$_3$O$_8$, MgScMo$_3$O$_8$, and Na$_3$Sc$_2$Mo$_5$O$_{16}$ with the same Mo$_3$O$_{13}$ magnetic building blocks. The crystal structures are characterized with x-ray or neutron powder diffraction and the magnetic ground states are determined by performing ac and dc susceptibility, specific heat, neutron powder diffraction, and $μ$SR measurements. Our work indicates that ZnScMo$_3$O$_8$ and MgScMo$_3$O$_8$ have ferromagnetic Curie-Weiss temperatures of 18.5 K and 11.9 K, ordered ground states with net moments (low-moment ferromagnetism or canted antiferromagnetism), and zero field ordering temperatures of $T_c =$ 6 K and $<$ 2 K respectively. On the other hand, Na$_3$Sc$_2$Mo$_5$O$_{16}$ hosts a dynamical magnetic ground state with no evidence for magnetic ordering or spin freezing down to 20 mK despite an antiferromagnetic Curie-Weiss temperature of -36.2 K, and therefore is a candidate for quantum spin liquid behavior. By comparing the present results to past work on the same family of materials, we construct a phase diagram which illustrates that the magnetic ground states of these Mo-based molecular magnets are very sensitive to small changes in the nearest neighbor Mo-Mo distance.

cond-mat.str-el↗

arXiv2024

Collective quantum phases in frustrated arrays of Josephson junctions

We study collective quantum phases and quantum phase transitions occurring in frustrated sawtooth arrays of small quantum Josephson junctions. Frustration is introduced through the periodic arrangement of $0$- and $π$- Josephson junctions with the Josephson coupling energies $αE_\mathrm{J}$ of different signs, $-1\leq α\leq 1$. The complexity of the potential landscape of the system is controlled by the frustration parameter $f=(1-α)/2$. The potential energy has a single global minimum in the non-frustrated regime ($f f_\mathrm{cr}=0.75$). We address the coherent quantum regime and identify several collective quantum phases: disordered (insulating) and ordered (superconducting) phases in the non-frustrated regime, as well as highly entangled patterns of vortices and anti-vortices in the frustrated regime. These collective quantum phases are controlled by several physical parameters: the frustration $f$, the Josephson coupling, and the charging energies of junctions and islands. We map the control parameter phase diagram by characterizing the quantum dynamics of frustrated Josephson junction arrays by spatially and temporally resolved quantum-mechanical correlation function of the local magnetization.

cond-mat.str-el↗

arXiv2025

Quasi-one-dimensional Supersolids in Luther-Emery Liquids

The supersolid is a long-sought phase in condensed matter physics, characterized by the coexistence of density wave and superfluid orders. This phase is counterintuitive, as different symmetry-breaking orders typically compete with one another. A deeper understanding of how such a state forms in condensed matter systems remains an open question, especially in quasi-one-dimensional correlated systems. In this work, we investigate the emergence of supersolids in Luttinger-Emery liquids using a variational method. As the system consists of coupled Luttinger-Emery liquid chains, we refer to this phase as a quasi-one-dimensional supersolid. Notably, we demonstrate that the quasi-one-dimensional supersolid phase is energetically favorable in chains with finite size or short-range order. Furthermore, we investigate the collective dynamics of these coexisting charge density waves and superconducting states, identifying a quasi-Goldstone mode. Our theory provides valuable insights into both the ground state and the dynamic properties of supersolids in strongly correlated systems.

cond-mat.str-el↗

arXiv2026

Interaction-Split Edge Spectral Flow in an Integer Hubbard Thouless Pump

We show that local Hubbard correlations can split the open-boundary spectral flow of an otherwise integer Thouless pump. Using density-matrix renormalization group calculations for a period-three Hubbard chain with a sliding onsite-repulsion modulation, we identify at filling $ρ=2/3$ a correlated insulating pump with many-body Chern number $C=+2$, corresponding to two units of charge transported per cycle. A spin-degenerate Hartree/Aubry--André--Harper reference model realizes the same integer response through simultaneous edge spectral flow in two independent spin channels. In the full Hubbard model, however, this integer bulk pump is implemented differently at an open boundary: the edge flow separates into two boundary events, and the intervening low-energy state is a nearly charge-neutral triplet edge excitation. Thus the quantized bulk charge transport remains integer, but local correlations reorganize its boundary realization into separated charged and neutral spinful sectors.

cond-mat.str-el↗

arXiv2026

Strange Luttinger liquids in a cavity-embedded one-dimensional electronic chain

We study a one-dimensional electronic chain coupled to a homogeneous quantized vacuum field and electron-electron interactions. In the absence of the latter, we derive a low-energy effective description in the presence of light-matter coupling, which we identify as a strange Luttinger liquid. Although it retains a formal resemblance to conventional Luttinger liquid theory, the coupling to the quantum field qualitatively modifies the low-energy sector and breaks the standard velocity relation underlying Luttinger universality. For finite electron-electron interactions, we recover a phase diagram featuring several phases as a function of interaction strength and hopping amplitude, including a phase hosting Majorana-like zero modes. Using exact diagonalization, we compute observables that characterize the phase boundaries and show that the cavity field significantly shifts them. We also study the fate of Majorana-like states under the influence of the cavity field, highlighting their modification by light-matter coupling. Finally, we investigate whether the strange Luttinger liquid description identified in the noninteracting regime continues to hold when electron-electron interactions are introduced.

cond-mat.str-el↗

arXiv2026

Observation of Flat Bands in Type-II Weyl Semimetal TaRhTe$_{4}$

Flat bands have been theoretically predicted for decades but have only recently been realized in quantum materials such as magic-angle twisted bilayer graphene, kagome and Lieb lattices, and rare-earth metal compounds. To date, only twisted layered materials have enabled tuning of flat-band energies near the electronic chemical potential, thereby influencing transport and thermodynamic properties. Here, we report the presence of flat bands near the chemical potential in bulk TaRhTe$_{4}$, a noncentrosymmetric van-der Waals type-II Weyl semimetal. Flat bands are rarely observed in Weyl semimetals, particularly in nonmagnetic bulk systems, and the observed flat bands were not predicted by density functional theory calculations. TaRhTe$_{4}$ therefore provides a platform in which nontrivial topology coexists with flat bands near the Fermi level, as evidenced by our angle-resolved photoemission spectroscopy measurements.

cond-mat.mtrl-sci↗

arXiv2026

Torus Berry Data Determine All-Genus Abelian Topological Orders

We show that for Abelian Chern-Simons topological orders, torus Berry matrices determine the all-genus extended TQFT. We identify the topological part of the projective Berry holonomy under metric deformations with the mapping-class-group representation of the Abelian Chern-Simons TQFT and prove that the normalized torus data reconstruct its finite quadratic module (G,q). Recent work showed that (G,q) classifies the extended theory up to symmetric monoidal natural isomorphism, and that the associated Abelian defect extension is determined by the pointed modular category C(G,q) arising from the same finite quadratic-module data. Therefore genus-one Berry data determine not only the all-genus bulk theory but also its associated defect structures without choosing a K-matrix presentation. We also prove that, for normalized character row errors $δ$<21.96%, nearest-row decoding recovers the Abelian fusion algebra independently of the number of anyons. The result applies to Abelian fractional quantum Hall and spin-liquid phases described by even-lattice Chern-Simons theories.

cond-mat.str-el↗

arXiv2026

HyperDet Wavefunction: A Phase-Agnostic Ansatz for Strongly Correlated Systems

Competing phases of strongly correlated systems are often described by trial wavefunctions built on phase-specific assumptions. We propose the \emph{hyperdeterminant (HyperDet) wavefunction} as a phase-agnostic ansatz for both bosonic and fermionic quantum many-body systems exhibiting spontaneous symmetry-breaking, fractionalization, and/or topological order. The HyperDet structure emerges by fusing auxiliary fermionic parton Slater determinants into physical orbitals through a learnable \emph{fusion tensor $\mathcal F$}. Optimized using variational Monte Carlo, a single HyperDet architecture achieves overlaps exceeding $99.9\%$ with exact-diagonalization ground states for nearly all sampled parameters across fractional Chern insulator (FCI) phases and their neighboring competing phases in both bosonic and fermionic models. Beyond its variational expressiveness, the optimized fusion tensor also provides rich interpretability. We show that, (i) the singular-value spectra of the \emph{bipartite fusion matrix} can be used to track phase transitions; (ii) the reconstructed Bott indices reproduce the parton Chern numbers expected for the FCI states without parton-Hamiltonian input; and (iii) faithful lifts of physical translations to the parton degrees of freedom recover the expected translation fractionalization in the bosonic FCI without projective symmetry class assignment. These results establish HyperDet wavefunction as a promising framework for both variational ground-state searches and phase-diagram explorations across strongly correlated phases, and for providing theoretical insights by connecting the optimized wavefunction with parton microscopics and field-theory descriptions.

cond-mat.str-el↗

arXiv2026

Robust Strange Metallicity across Attractive and Repulsive Hubbard Models

Using determinant quantum Monte Carlo simulations, we compare charge transport in the two-dimensional attractive and repulsive Hubbard models at strong coupling, $|U|/t=6$. Although the interaction with opposite signs generates qualitatively different low-energy spin, charge, and pairing correlations, both exhibit approximately linear-in-temperature resistivity over a broad intermediate- and high-temperature regime. At asymptotically high temperature this common behavior follows from the moment expansion of the conductivity, whose leading contribution is even in $U$. More strikingly, the similarity persists to temperatures well below $|U|$, where strong interaction-dependent correlations have already developed, and also irrespective of whether resistivity crosses the MIR limit. Using the Nernst--Einstein relation, we find that the common linear-in-temperature resistivity is primarily associated with an approximately Curie-like charge compressibility and weakly temperature-dependent diffusivity. The two models separate only at lower temperatures, where the attractive model develops a pronounced feature in the charge diffusivity correlated with signatures of pair formation. These results show that linear-in-temperature incoherent transport in the Hubbard model can be remarkably insensitive to the microscopic nature of the low-energy correlations. Our results suggest that transport in the incoherent regime appears insensitive to what the system will ultimately become at low temperature; the distinction between competing low-energy states becomes visible only when their characteristic correlations acquire sufficiently long spatial or temporal coherence.

cond-mat.str-el↗

arXiv2026

Spin Configurations of Anyonic excitations in Moiré Fractional Chern Insulators

We have examined the nature of elementary excitations in particular, their spin polarization, in recently discovered zero-field fractional Chern insulator in twisted bilayer MoTe$_2$. We have found that the finite-size bilayer system, in close proximity to a planar parabolic quantum dot containing a single electron (or a hole), forms an incompressible spin-unpolarized fractional Chern insulator at 1/3 filling factor. The corresponding energy gap is found to be large and weakly dependent on the separation between the quantum dot and the bilayer. We predict that in this fractional Chern insulator coupled to a quantum dot, spin-unpolarized quasiparticles and quasiholes are expected to appear as low-energy elementary excitations. The charge density results indicate that, for the spin-unpolarized quasiparticles, the positive charge is strongly localized near the negatively charged QD within the spin-flipped component, whereas for the spin-polarized quasiparticles, such localization is much less pronounced.

cond-mat.str-el↗