arXiv subjects

Alberto Nardin

Publications and source records attributed to Alberto Nardin.

15 recordsLinked to original sources

arXiv2026

Hall viscosity from metric-sensitive dichroic probes

Hall viscosity characterizes the geometric response of a quantum Hall droplet to deformations of the underlying metric, yet it has remained difficult to measure directly. We propose a spectroscopic probe based on circular dichroism, using chiral metric-sensitive drives -- implemented as rotating quadrupolar ("saddle") perturbations -- that effectively modulate the metric and couple to the generators of area-preserving deformations. The resulting dichroic signal directly measures the Hall viscosity, while frequency-resolved spectroscopy disentangles it from other excitations. A local formulation further enables spatially resolved markers of Hall viscosity applicable to both continuum and lattice systems. Our results open a direct route to measuring Hall viscosity in quantum-engineered platforms such as cold atoms in optical lattices.

cond-mat.mes-hall↗

arXiv2026

Perfect elliptic dichroism: Probing the metric of anisotropic quantum Hall droplets

Understanding the geometry of quantum Hall systems is a central challenge in modern condensed matter physics. We introduce a framework for probing the geometric structure of quantum Hall droplets by engineering the geometry of a dichroic probe and identifying the onset of "perfect elliptic dichroism", a regime in which the system responds exclusively to an elliptically polarized drive of a given chirality. This phenomenon provides a direct diagnostic of the droplet's intrinsic metric, and we show that it extends naturally to ideal Chern bands, where holomorphicity of the occupied states guarantees the vanishing of one chiral absorption rate with a quantized response for the other. In lattice realizations, such as the Harper-Hofstadter model, finite lattice-spacing corrections break the exact continuum metric description and give rise to a renormalized, emergent Landau-orbit metric; the probe ellipticity at which perfect dichroism is achieved then shifts accordingly, offering a direct spectroscopic window onto this lattice-induced geometric renormalization. Our results illuminate the rich geometric structure of quantum Hall phases and offer concrete pathways for observing these effects in quantum-engineered platforms.

cond-mat.mes-hall↗

arXiv2026

Fate of a Fractional Chern Insulator under Nonlocal Interactions in Synthetic Dimensions

Synthetic dimensions provide a powerful route to engineer topological lattice models in ultracold atomic systems, but they contain intrinsic nonlocal interactions along the synthetic direction. We investigate an extended Harper-Hofstadter model subject to infinite-range column interactions that mimic this synthetic nonlocality. By tuning this interaction strength, we demonstrate an adiabatic evolution from a Laughlin-type bosonic fractional Chern insulator to a charge-ordered Tao-Thouless-like state without closing the many-body gap. Along this path, the many-body Chern number and the topological entanglement entropy remain unchanged, despite a pronounced restructuring of the entanglement spectrum and the loss of robustness against local perturbations. This adiabatic connectivity establishes a controlled bridge between topologically ordered and effect- ively one-dimensional charge-ordered regimes, opening potential new avenues for state preparation. Our results also show that conventional topological markers may fail to diagnose the breakdown of locality-protected topological order in synthetic dimensions, and identify nonlocal interactions as a powerful knob to coherently interpolate between distinct many-body regimes.

cond-mat.quant-gas↗

arXiv2026

Open quantum spin chains with non-reciprocity: a theoretical approach based on the time-dependent generalized Gibbs ensemble

We study an open quantum spin chain with non-reciprocal dissipation using a theoretical approach known as time-dependent generalized Gibbs ensemble. In the regime of weak dissipation the system is fully characterized by its rapidity distribution and we derive a closed set of coupled differential equations governing their time evolution. We check the accuracy of this theory by benchmarking the results against numerical simulations. Using this framework we are able to compute both the magnetization density and current dynamics, identifying some relations between the two. The problem of the anomalous power-law exponents identified in a previous work is discussed. Our work constitutes a theoretical approach that is able to describe the physics of non-reciprocal open quantum spin chains beyond analyses based on non-interacting fermions.

quant-ph↗

arXiv2025

Electrostatics-induced breakdown of the integer quantum Hall effect in cavity QED

We address the prevailing theoretical explanation of the recently observed breakdown of the integer quantum Hall effect in a two-dimensional electron gas embedded in a metallic split-ring resonator. Within the same single-particle description of quantized Hall conductance, we compare previously proposed vacuum-induced transport modifications against an alternative mechanism that explains this breakdown in terms of non-chiral edge channels arising solely from electrostatic boundary effects. This direct comparison shows that for experimentally relevant parameters, the electrostatic contribution exceeds that of any vacuum-induced conductance modifications by many orders of magnitude and yields characteristic transport signatures and energy scales that align well with experimental observations. This finding sheds new light on this puzzling phenomenon, supporting an electrostatic rather than a vacuum-related interpretation that can be directly tested in experiments.

cond-mat.mes-hall↗

arXiv2025

$\mathrm{SU}(3)$ Fermi-Hubbard gas with three-body losses: symmetries and dark states

We study an $\mathrm{SU}(3)$ invariant Fermi-Hubbard gas undergoing on-site three-body losses. The model presents eight independent strong symmetries preventing the complete depletion of the gas. By making use of a basis of semi-standard Young tableaux states, we reveal the presence of a rich phenomenology of stationary states. We classify the latter according to the irreducible representation of $\mathrm{SU}(3)$ to which they belong. We finally discuss the presence of three-particle stationary states that are not protected by the $\mathrm{SU}(3)$ symmetry.

cond-mat.quant-gas↗

arXiv2024

Spin fractionalization at the edge of quantum Hall fluids induced by bulk quasiparticles

We define a measurable spin for the edge of a lowest Landau level and incompressible fractional quantum Hall state in the presence of an Abelian or non-Abelian bulk quasiparticle. We show that this quantity takes a fractional value inherited from the fractional spin of the bulk quasiparticle. We present a geometric picture that does not rely on global symmetries of the wavefunction but is able to treat quasiparticles and edges with different shapes. We study finite-size many-body wavefunctions on the cylinder with circular quasiparticles and straight edges. Our results are supported by matrix-product-state calculations for the Laughlin and the k=3 Read-Rezayi states.

cond-mat.str-el↗

arXiv2024

Universality and two-body losses: lessons from the effective non-Hermitian dynamics of two particles

We study the late-time dynamics of two particles confined in one spatial dimension and subject to two-body losses. The dynamics is exactly described by a non-Hermitian Hamiltonian that can be analytically studied both in the continuum and on a lattice. The asymptotic decay rate and the universal power-law form of the decay of the number of particles are exactly computed in the whole parameter space of the problem. When in the initial state the two particles are far apart, the average number of particles in the setup decays with time $t$ as $t^{-1/2}$; a different power law, $t^{-3/2}$, is found when the two particles overlap in the initial state. These results are valid both in the continuum and on a lattice, but in the latter case a logarithmic correction appears.

cond-mat.quant-gas↗

arXiv2024

Quantum nonlinear optics on the edge of a few-particle fractional quantum Hall fluid in a small lattice

We study the quantum dynamics in response to time-dependent external potentials of the edge modes of a small fractional quantum Hall fluid composed of few particles on a lattice in a bosonic Laughlin-like state at filling {\nu} = 1/2. We show that the nonlinear chiral Luttinger liquid theory provides a quantitatively accurate description even for the small lattices that are available in state-of-the-art experiments, away from the continuum limit. Experimentally-accessible data related to the quantized value of the bulk transverse Hall conductivity are identified both in the linear and the non-linear response to an external excitation. The strong nonlinearity induced by the open boundaries is responsible for sizable quantum blockade effects, leading to the generation of nonclassical states of the edge modes.

cond-mat.mes-hall↗

arXiv2023

Spin-statistics relation for quantum Hall states

We prove a generic spin-statistics relation for the fractional quasiparticles that appear in abelian quantum Hall states on the disk. The proof is based on an efficient way for computing the Berry phase acquired by a generic quasiparticle translated in the plane along a circular path, and on the crucial fact that once the gauge-invariant generator of rotations is projected onto a Landau level, it fractionalizes among the quasiparticles and the edge. Using these results we define a measurable quasiparticle fractional spin that satisfies the spin-statistics relation. As an application, we predict the value of the spin of the composite-fermion quasielectron proposed by Jain; our numerical simulations agree with that value. We also show that Laughlin's quasielectrons satisfy the spin-statistics relation, but carry the wrong spin to be the anti-anyons of Laughlin's quasiholes. We continue by highlighting the fact that the statistical angle between two quasiparticles can be obtained by measuring the angular momentum whilst merging the two quasiparticles. Finally, we show that our arguments carry over to the non-abelian case by discussing explicitly the Moore-Read wavefunction.

cond-mat.mes-hall↗

arXiv2023

Laughlin's quasielectron as a non-local composite fermion

We discuss the link between the quasielectron wavefunctions proposed by Laughlin and by Jain and show both analytically and numerically that Laughlin's quasielectron is a non-local composite fermion state. Composite-fermion states are typically discussed in terms of the composite-fermion Landau levels (also known as Lambda levels). In standard composite-fermion quasielectron wavefunctions the excited Lambda levels have sub-extensive occupation numbers. However, once the Laughlin's quasielectron is reformulated as a composite fermion, an overall logarithmic occupation of the first Lambda level is made apparent, which includes orbitals that are localized at the boundary of the droplet. Even though the wavefunction proposed by Laughlin features a localised quasielectron with well-defined fractional charge, it exhibits some non-trivial boundary properties which motivate our interpretation of Laughlin's quasielectron as a non-local object. This has an important physical consequence: Laughlin's quasielectron fractionalizes an incorrect spin, deeply related to the anyonic braiding statistics. We conclude that Laughlin's quasielectron is not a good candidate for a quasielectron wavefunction.

cond-mat.str-el↗

arXiv2023

Refermionized theory of the edge modes of a fractional quantum Hall cloud

Making use of refermionization techniques, we map the nonlinear chiral Luttinger liquid model of the edge modes of a spatially confined fractional quantum Hall cloud developed in our recent work [Phys. Rev. A 107, 033320 (2023)] onto a one-dimensional system of massive and interacting chiral fermions, whose mass and interactions are set by the filling factor of the quantum Hall fluid and the shape of the external confining potential at the position of the edge. As an example of the predictive power of the refermionized theory, we report a detailed study of the dynamic structure factor and of the spectral function of a fractional quantum Hall cloud. Among other features, our refermionized theory provides a physical understanding of the effective decay of the edge excitations and of the universal power-law exponents at the thresholds of the dynamic structure factor. The quantitative accuracy of the refermionized theory is validated against a full two-dimensional calculation based on a combination of exact diagonalization and Monte Carlo sampling.

cond-mat.str-el↗

arXiv2022

Linear and nonlinear edge dynamics of trapped fractional quantum Hall droplets

We report numerical studies of the linear and nonlinear edge dynamics of a non-harmonically confined macroscopic fractional quantum Hall fluid. In the long-wavelength and weak excitation limit, observable consequences of the fractional transverse conductivity are recovered. The first non-universal corrections to the chiral Luttinger liquid theory are then characterized: for a weak excitation in the linear response regime, cubic corrections to the linear wave dispersion and a broadening of the dynamical structure factor of the edge excitations are identified; for stronger excitations, sizable nonlinear effects are found in the dynamics. The numerically observed features are quantitatively captured by a nonlinear chiral Luttinger liquid quantum Hamiltonian that reduces to a driven Korteweg-de Vries equation in the semiclassical limit. Experimental observability of our predictions is finally discussed.

cond-mat.mes-hall↗

arXiv2020

Edge dynamics of an Integer Quantum Hall system

In this master thesis work the linear and non linear edge dynamics of a non-interacting system of fermions in a Integer Quantum Hall state is theoretically and numerically studied.

cond-mat.quant-gas↗

arXiv2020

Non-linear edge dynamics of an Integer Quantum Hall fluid

We report a theoretical study of the linear and nonlinear dynamics of edge excitations of an integer quantum Hall state of non-interacting fermions. New features beyond the chiral Luttinger liquid picture are anticipated to arise from the interplay of the curvature of the Landau level dispersion and of the Pauli exclusion principle. For long-wavelength perturbations, the microscopic numerical results are captured by a chiral nonlinear hydrodynamic equation including a density-dependent velocity term. In the wave-breaking regime, shock waves are found to be regularized into a complex ripple pattern by dispersion effects. Our results are of specific relevance for experiments with synthetic quantum matter, in particular ultracold atomic gases.

cond-mat.quant-gas↗