arXiv subjects

Taige Wang

Publications and source records attributed to Taige Wang.

At least 19 recordsLinked to original sources

arXiv2026

Establishing Néel order in the square-lattice antiferromagnetic Heisenberg model: a bootstrap proof

Rigorously establishing spontaneous symmetry breaking (SSB) in the thermodynamic limit is generally challenging. This is exemplified by the two-dimensional (2D) $S = 1/2$ antiferromagnetic Heisenberg model where the existence of Néel order is not rigorously established despite overwhelming evidence from a variety of methods. We show that a bootstrap approach can be used to rigorously establish SSB and use it to prove the existence of Néel order in the 2D $S = 1/2$ XXZ model by deriving a strictly positive lower bound on the Néel order parameter for a set of discrete values of the anisotropy parameter $Δ$ in the range $[0,2]$ including the isotropic (Heisenberg) point $Δ= 1$. Our approach employs a generalization of the Kennedy--Lieb--Shastry inequalities, which use an infrared bound to reduce the existence of long-range order to bounds on certain finite-distance correlators. We compute these bounds for all sufficiently large systems with periodic boundary conditions using the bootstrap. An important ingredient in our proof is a novel method for obtaining exactly certified variational upper bounds on the energy density in the thermodynamic limit from matrix product states. Our approach can be readily generalized to other local lattice models for which infrared susceptibility bounds can be obtained.

cond-mat.stat-mech↗

arXiv2026

Repulsion-Driven Topological Superconductivity in Twisted MoTe$_2$

We show that a microscopic model of twisted MoTe$_2$ with screened Coulomb interactions produces topological superconductivity. Using the density matrix renormalization group (DMRG) on infinite cylinders, we find that the narrow Chern band of twisted MoTe$_2$ has Cooper pair correlations that strengthen with cylinder circumference, consistent with two dimensional superconductivity. The superconductor has chiral $f$-wave pairing around the valley center, and its topology produces chiral Majorana edge modes and non-Abelian vortex cores. At zero displacement field, the superconductor spans fillings $-0.78\lesssimν\lesssim-0.72$, close to the experimental range, and extends in a dome to finite displacement field. We then predict how its stiffness evolves with the filling and the tunable displacement field. The interplay with screening length is also examined. Nearby, we find a fractional Chern insulator, a topological charge density wave, a metal, and a charge-ordered state. The last is a candidate for the reentrant integer Hall regime in experiments. These results establish a route from repulsive interactions in microscopic models of moiré materials to chiral topological uperconductors with chiral Majorana edge modes.

cond-mat.str-el↗

arXiv2026

Revisiting monodromy defects in $\text{O}(N)$ conformal field theories

Monodromy defects are fundamental objects in extended quantum systems with global symmetries. We study such defects in $\text{O}(N)$ conformal field theories (CFT), which describe the universality class of $\text{O}(N)$ spontaneous symmetry breaking transitions. In particular, we consider partial-monodromy defects, whose corresponding symmetry transformations only act on a subset of the fundamental $\text{O}(N)$ vector field. We develop an analytical theory of the defect phases, using both renormalization group and large $N$ expansion. In general (spacetime) dimensions $3\leq d<4$, multiple defect CFTs are identified, which are described by appropriate boundary conditions for the vector field near the defect. Near $d=3$, we show that in the large $N$ limit, a stable defect CFT always exists, characterized by the so-called ("standard") "alternate" boundary conditions for the (twisted) untwisted fields, whose defect correlations are (suppressed) enhanced. We then perform large-scale classical Monte Carlo simulations of monodromy defects in the O(3) CFT in an improved lattice model and numerically extract the defect scaling dimensions. The numerical results are in qualitative agreement with the stable defect CFT identified in the field theory.

hep-th↗

arXiv2026

Solving fractional quantum Hall problems with thermodynamic-limit bootstrap

Determining correlated ground states directly in the thermodynamic limit remains a central challenge in quantum many-body physics. Here we develop a quantum many-body bootstrap that yields a rigorous and tight lower bound on the thermodynamic ground-state energy of a fractional quantum Hall system together with an optimized reduced density matrix $ρ_W^\star$ on a spatial window. For sufficiently tight bounds, we find that $ρ_W^\star$ accurately reproduces the ground-state reduced density matrix, as directly tested by its fidelity with known model states. For exactly solvable Laughlin and Moore--Read parent Hamiltonians, the bootstrap also reproduces pair correlations and orbital entanglement spectra (OES). For Landau-level-projected Coulomb interactions across multiple fillings, the energy bounds closely track established thermodynamic estimates, while the window density matrix recovers the familiar $ν=1/3$ Laughlin and $ν=5/2$ Moore--Read states and the composite Fermi liquid at $ν=1/2$. More importantly, the same framework also resolves unsettled regimes. At $ν=1/4$, the OES and real-space correlations identify a composite Fermi liquid, while at $ν=12/5$ the combined diagnostics suggest $\overline{\mathrm{RR}}_3$ as the ground-state order. Our bootstrap therefore provides direct access to both ground-state energies and many-body structure in the thermodynamic limit.

cond-mat.str-el↗

arXiv2026

Single anyons and anyon binding in a quantum Hall dot

Anyons are particles with quantized fractional statistics. In theory, a single anyon can be stabilized as a localized fractional charge within the bulk of a topologically ordered two-dimensional insulator. However, experiments to date have focused on probing anyons in structures in which many anyonic excitations coexist and interact. Here, we demonstrate the trapping of a single anyon in a device consisting of a graphene-based quantum point contact with an embedded tunable quantum Hall dot. Benchmarking our device at v = 1, we demonstrate backscattering between Fermi liquid edge states mediated by the whole-electron Coulomb blockade of the dot. The cleanliness and control available in our device allow depletion of the dot to the last quasihole, and we observe spin blockade for transitions to the opposite-spin Landau level. At v = 1/3 and 2/3, we observe backscattering resonances with three times the frequency, consistent with resonant transmission of e/3 charges via a single anyon transistor. We demonstrate controlled depletion to the last quasiparticle to form a single anyon quantum dot. Tracing the charge addition spectrum for quasiparticle number Nqp = 1-5, we observe highly irregular addition energies, consistent with DMRG modeling showing a complex orbital shell-filling behavior. At higher Nqp = 10-20, the addition energies show a striking pattern: quasiholes at 1/3 (and quasiparticles at 2/3) show a regular addition spectrum while quasiparticles at 1/3 (and quasiholes at 2/3) do not. We trace the origin of this irregularity to an attractive component of the inter-anyon interaction: by experimentally tuning the confining energy, we observe complete suppression of alternating charge sectors, after which the dot charges in increments of twice the fundamental charge. This observation indicates the emergence of an anyon binding energy as large as the charging energy.

cond-mat.mes-hall↗

arXiv2026

Interacting Chern insulator transition on the sphere: revealing the Gross-Neveu-Yukawa criticality

In two spatial dimensions, the transition between topological and trivial Chern insulators exemplifies a class of beyond-Landau critical phenomena. We show that the interaction-driven multicritical point of this transition falls into the Gross-Neveu-Yukawa (GNY) universality class, a topic of considerable interest in both high-energy and condensed matter physics. In this work, we focus on the $N=2$ case of the GNY criticality. We employ exact diagonalization of Dirac fermions on a sphere to circumvent the parity anomaly, capitalize on full $SO(3)$ symmetry to reduce finite-size effects, and directly extract operator scaling dimensions from the excitation spectrum. Despite working with only modest system sizes, our results closely match conformal bootstrap predictions for low-scaling dimension operators and reveal several previously uncharacterized higher primaries. These findings highlight the efficacy of spherical geometry for probing interacting Dirac criticality.

cond-mat.str-el↗

arXiv2026

Topological superconductivity from Abelian fractional Chern insulators

Can a Laughlin anyon fluid become a topological superconductor? We answer this question for a $ν=1/3$ fractional Chern insulator (FCI) using a $U(3)$ infrared parton theory. Three charge-$e/3$ constituents form the electron, while three constituent pairs form a gauge-invariant charge-$2e$ Cooper pair. The resulting superconductors share an ordinary charge-$2e$ sector but differ in their neutral color response, giving an SC$^\ast$ with the parent Laughlin $U(1)_3$ order, a chiral topological superconductor with $c_-=3/2$, and a strong-pairing molecular superconductor with $c_-=3$. The same framework organizes a nearby $σ_{xy}=0$ charge density wave (CDW) state. At commensurate filling, the normal state and the $c_-=3$ and $c_-=3/2$ superconducting descendants are naturally tied to a period-three density order background, while the SC$^\ast$ branch can preserve microscopic translations. Away from commensuration, a chargon metal can pair into the same $c_-=3/2$ topological superconductor. The FCI, reentrant CDW, and chiral superconductivity are unified in the $U(3)$ parton theory.

cond-mat.str-el↗

arXiv2026

Entangling power of neural networks

Characterizing the complexity of correlations between subsystems is a fundamental task across information theory, machine learning, and science. In quantum physics, neural networks have found increasing application in learning wavefunctions. Here we introduce the entangling power of an encoder-decoder neural network, which quantifies its ability to generate entanglement between subsystems, dependent on a latent space dimension $K$ and the complexity class of the decoder. We exactly calculate this quantity for polynomial decoders of degree $p$ acting on a $K$-dimensional latent space. Our results establish the exponential entangling power of neural networks with modest resources. More broadly, our work provides a framework for analyzing correlations in machine learning that generalizes the notion of the Schmidt rank in entanglement theory.

cond-mat.dis-nn↗

arXiv2026

Periodic solution and its stability of a damped BBM equation posed on $\mathbb{T}$

In this paper, we are concerned with the existence and stability of temporal periodic solutions to a class of the Benjamin-Bona-Mahony (BBM) equation with damping in the torus $\mathbb{T}$, whose interior is applied with periodic force $f(x, t)$ with temporal period $θ$. These types of solutions are established in $H^{\ell}, \ell\ge 0$, and it is noteworthy to see that the I-energy method is invoked when low regularity of $\ell\in[0, 1)$ is pursued.

math.AP↗

arXiv2026

Quantum Mott semimetal in a one-dimensional Hubbard model

Mott physics in topological bands has recently attracted considerable attention, particularly in the context of twisted bilayer graphene (TBG). However, the essential ingredients for stabilizing this physics remain unclear. Here, we demonstrate a quantum Mott semimetal phase as the ground state within a one-dimensional spinful Hubbard model featuring only one orbital per unit cell, protected by inversion and particle-hole symmetries. We start from a two-orbital model where a localized $f$ orbital on the A sublattice hybridizes with a delocalized $c$ orbital on the B sublattice. Projecting the $f$-orbital Hubbard $U$ onto the active flat band yields a lattice model with Wannier orbitals centered on the B sublattice. Similar to TBG, a momentum-space scale $k_*$ emerges, setting the interaction range in the projected model to $1/k_*$. While the ground state is ferromagnetic with only the Hubbard $U$, introducing an inter-site antiferromagnetic spin coupling $J$ stabilizes a Mott semimetal$^*$ phase with a central charge $c=3$. Using exact diagonalization (ED) and density matrix renormalization group (DMRG) methods, we show that this phase hosts a spinful Dirac fermion coexisting with a neutral spin mode -- analogous to the fractionalized Fermi liquid (FL$^*$) phase in higher dimensions. Furthermore, breaking particle-hole (PH) symmetry via dispersion transforms the Mott semimetal into a Mott insulator, which is separated from a distinct Mott insulating phase by a continuous transition with a polarization jump of $1/2$. Our work provides the first unbiased evidence of a Mott semimetal ground state and demonstrates that this 1D model captures some essential aspects of TBG physics, despite lacking a Wannier obstruction.

cond-mat.str-el↗

arXiv2026

Propagating Collective Spin-valley Modes in Twisted WSe2

The emergence of neutral collective modes is a hallmark of correlated quantum phases but is often challenging to probe experimentally. In two-dimensional flatband systems, charge responses have been intensively investigated yet neutral excitations remain largely unexplored. In particular, intervalley coherent state (IVC) features a neutral Goldstone mode due to spontaneously broken valley U(1) symmetry. While IVC state has been proposed as a unifying theme across graphene and semiconductor based systems, its defining feature, the neutral Goldstone mode, remains elusive in experiment. Here we investigate space and time resolved transport of neutral modes in twisted WSe2 moire superlattices through a novel ultrafast imaging technique. We uncover two new propagating collective modes with very different velocities, which emerge near the van Hove singularity (VHS) in both intermediate (3.5 to 4 degree) and large (around 5 degree) angle twisted WSe2. The fast-propagating mode has a large speed of about 3 km/s and is consistent with a Goldstone mode for an IVC state, while the slow-moving mode is likely a gapped amplitude mode. They can be understood as the spin-valley analogues of collective modes of a superfluid, whose propagation is imaged for the first time in a condensed matter system. Our study demonstrates a powerful new approach for probing charge-neutral modes in quantum materials and offers key insights into the interplay between charge and spin-valley physics in moire superlattices.

cond-mat.mes-hall↗

arXiv2026

Simulating quantum circuits with a neural statebank

Predicting the output of quantum circuits is a central bottleneck for verifying quantum processors because a generic wavefunction grows exponentially with system size. We introduce a neural statebank that learns this wavefunction along the circuit trajectory. Each layer is stored as an autoregressive Transformer checkpoint trained from local gate updates to the preceding checkpoint, producing a compact neural representation that can evaluate amplitudes and generate independent samples. On long-range circuits combining entanglement, magic, and non-diagonal branching, a 0.3-million-parameter statebank reaches $\sim 10^{-2}$ infidelity at 34 qubits, outperforming the other tested approximate simulators while using far less memory than exact state-vector evolution. The same architecture accurately simulates quantum approximate optimization, Clifford+$T$, and Clifford circuits.

quant-ph↗

arXiv2026

Measuring anyon dispersion with tunneling probes

Anyons are usually characterized by their topological data and their fractional quantum numbers under global symmetries. In lattice systems such as fractional Chern insulators (FCI), they are also mobile quasiparticles. Their motion controls the possible ground states of the dilute anyon gas obtained by doping an FCI, including possible superconducting states. We show how tunneling probes can measure this motion. In scanning tunneling spectroscopy, weak disorder produces spatially oscillating quasiparticle-interference patterns whose branches reveal the dispersion of fractionalized constituents. In quantum twisting microscopy, planar momentum-conserving tunneling selects the total momentum of the injected electron, so the continuum thresholds of fractionalized electron spectra encode the dispersion of the constituent anyons. The resulting spectra distinguish compact electron-like excitations, bound anyon molecules, and unbound anyon continuum.

cond-mat.mes-hall↗

arXiv2026

Van Hove Singularity-Driven Topological Magnetism in Twisted MoTe2

Van Hove singularities (vHSs) strongly amplify electron interactions and can stabilize correlated phases in topological bands. Here we report signatures of topological magnetism in large-angle twisted bilayer MoTe2 driven by the interplay of vHSs, strong correlations, and valley topology. In a 4.8 degree device, electrostatic tuning to a vHS produces a spontaneous anomalous Hall hot spot near nu = -1. Combined transport and reflective magnetic circular dichroism measurements indicate that this regime is not governed by magnetization alone, but instead emerges from a correlated intervalley-coherent antiferromagnetic state that evolves with doping into a canted phase. With increasing magnetic field, the Hall response develops an additional finite-field component consistent with a topological Hall effect from a noncoplanar spin texture, before transitioning into a C = -1 Chern insulator. Our results establish tunable vHSs in moire topological bands as a route to chiral magnetism and engineering topological phase transitions.

cond-mat.mes-hall↗

arXiv2026

Studying 3D O(N) Surface CFT on the Fuzzy Sphere

Boundary conformal field theory (BCFT) provides a universal framework for critical phenomena in the presence of boundaries. We determine BCFT data for the normal and ordinary boundary universality classes of the $1+1$-dimensional boundaries of the $2+1$-dimensional $O(2)$ and $O(3)$ Wilson-Fisher fixed points, realized microscopically by a bilayer Heisenberg model on the fuzzy sphere. Using the fuzzy-sphere state-operator correspondence, we obtain boundary operator spectra, identify low-lying boundary primary operators, extract operator-product-expansion (OPE) data, and estimate the boundary central charges for both boundary conditions. For the normal boundary condition, the universal amplitudes $a_σ$ and $b_t$ extracted from one- and two-point functions agree quantitatively with Monte Carlo benchmarks where available. For both $N=2$ and $N=3$, we find a positive extraordinary-log exponent $α$, providing independent microscopic evidence for extraordinary-log boundary criticality. Our results extend fuzzy-sphere BCFT spectroscopy beyond the Ising universality class to continuous $O(N)$ symmetry.

cond-mat.str-el↗

arXiv2026

Anyon superfluidity of excitons in quantum Hall bilayers

The charged anyons of a fractional quantum Hall fluid are necessarily dispersionless due to the continuous magnetic translation symmetry. Neutral anyons, however, can disperse, resulting in a much richer space of possible ``daughter'' states when doped to finite density. We discuss a natural realization of such physics in quantum Hall bilayers, where a finite density of excitons with fractional statistics is argued to give rise to `anyonic exciton superfluidity,' the charge-neutral analog of anyon superconductivity. In a balanced bilayer of two Laughlin $ν= 1/3$ states, the minimal interlayer exciton carries anyonic exchange statistics. A finite density of these excitons is argued to yield an exciton superfluid stitched to a specific bulk topological order and edge spectrum. Such superfluidity should be most robust near the direct transition into the Halperin $(112)$ state, and near analogous transitions in the bilayer Jain sequence at total filling $ν_\text{T} = 2\times \frac{n}{2n+1}$. These topological transitions can be described by Chern-Simons QED$_3$, from which we derive several novel and general properties of anyon superfluidity near such transitions, including an anomalously large superfluid stiffness of $κ_\text{s} \propto |δν|^{1/2}$ at layer imbalance fraction $δν$. A notable feature of the phase diagrams we construct is the prevalence of spatial symmetry breaking, driven by an underlying composite Fermi surface. Our results can be directly tested with currently available experimental techniques. We compare our theory with existing data and make concrete predictions for future measurements, including higher-pseudospin exciton superfluids when doping higher Jain fractions.

cond-mat.str-el↗

arXiv2026

Anyon molecules in fractional quantum Hall states

We use segment DMRG on the infinite cylinder to compute energies of charged excitations in gate-screened fractional quantum Hall states. For the $ν=1/3$ Laughlin, $ν=2/5$ Jain, and $ν=5/2$ anti-Pfaffian states, we find screening can bind like-charged anyons into molecules, with a strong dependence on filling-factor, gate distance, and fusion channel. In the Laughlin state, stable $\pm 2e/3$ molecules and larger clusters appear over a broad gate-distance window. The Jain state is molecular throughout the range we consider. In the anti-Pfaffian, binding is strongest on the hole side, where the charge-$e/2$ molecule is fused into the $ψ$ channel over a broad window of gate distances. In all three cases, screening suppresses long-range repulsion and exposes an intermediate-range attraction encoded in the oscillatory density tail of the fundamental anyon. We discuss consequences for addition spectra, interferometry, Wigner crystallization, anyon superconductivity, and entropy measurements.

cond-mat.mes-hall↗

arXiv2026

Expressibility of neural quantum states: a Walsh-complexity perspective

Neural quantum states are powerful variational wavefunctions, but it remains unclear which many-body states can be represented efficiently by modern additive architectures. We introduce Walsh complexity, a basis-dependent measure of how broadly a wavefunction is spread over parity patterns. States with an almost uniform Walsh spectrum require exponentially large Walsh complexity from any good approximant. We show that shallow additive feed-forward networks cannot generate such complexity in the tame regime, e.g. polynomial activations with subexponential parameter scaling. As a concrete example, we construct a simple dimerized state prepared by a single layer of disjoint controlled-$Z$ gates. Although it has only short-range entanglement and a simple tensor-network description, its Walsh complexity is maximal. Full-cube fits across system size and depth are consistent with the complexity bound: for polynomial activations, successful fitting appears only once depth reaches a logarithmic scale in $N$, whereas activation saturation in $\tanh$ produces a sharp threshold-like jump already at depth $3$. Walsh complexity therefore provides an expressibility axis complementary to entanglement and clarifies when depth becomes an essential resource for additive neural quantum states.

cond-mat.str-el↗