Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2611.08479

Flat-band systems: A platform to realize the moments of Quantum Metric

Rishi Gangadhar·Binayyak Roy·Vito Scarola·Sumanta Tewari
View original source ↗Read source document ↗Export metadata ↓

Abstract

The quantum metric is a fundamental geometric property of Bloch bands that governs a wide range of physical phenomena, yet experimentally accessing it remains challenging. We show that the momentum-space variation of the quantum metric can be probed through the real-space dynamics of a Gaussian wave packet prepared in an isolated flat band. Following the application of a weak constant force, we demonstrate analytically that the leading order change in the wave-packet variance is linear in time and contains a contribution proportional to the wave-packet averaged gradient of the quantum-metric trace. This geometric contribution remains finite despite the absence of band dispersion. We illustrate the effect using a gapped Lieb lattice with an exactly flat middle band and vanishing Berry curvature, allowing the quantum-metric contribution to the spreading to be isolated. The numerical results agree with the analytical prediction and confirm the quantum-metric contribution to the wave-packet spreading. The required lattice preparation, tunable hopping amplitudes, applied force, and density measurements are compatible with established ultracold-atom techniques, providing a possible platform for observing the predicted response. Our results establish wave-packet spreading as a dynamical probe of quantum geometry in flat-band systems.

Explore related subjects

cond-mat.quant-gas

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Rishi Gangadhar, Binayyak Roy, Vito Scarola, Sumanta Tewari. 2026-11-05. Flat-band systems: A platform to realize the moments of Quantum Metric. https://arxiv.org/abs/2611.08479

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Exact quantum geometry from sublattice symmetry: Closed-form solution of the quarter-flux Harper-Hofstadter model

Quantum geometry has emerged as a guiding principle across atomic and condensed-matter physics, shaping the topological responses of Bloch bands and the stability of the correlated phases they host. Sublattice symmetry, though common among bipartite lattice models, has not yet been exploited to obtain closed-form quantum geometry in multiband systems. For this purpose, we derive a general expression for the QGT of sublattice-symmetric systems in terms of contributions from the individual sublattice sectors, and show that this symmetry renders the Bloch Hamiltonian of a paradigmatic four-band model, the quarter-flux Harper-Hofstadter model, anti-block-diagonal, analytically yielding the spectrum, eigenstates, and full quantum geometric tensor (QGT), including the Berry curvature and quantum metric, for all four bands. The model, describing charged particles on a two-dimensional square lattice subjected to a uniform magnetic field, has recently been realized experimentally with ultracold atoms, photons, and superconducting circuits. Finally, we evaluate fractional-Chern-insulator stability criteria analytically and quantify the lowest band of the quarter-flux Harper-Hofstadter model to be a nearly ideal Chern band. Our approach opens a route for studying also the quantum geometry of other sublattice-symmetric multiband systems.

cond-mat.quant-gas↗
arXiv2026

Motion-Induced Polaron Resonance beyond the Orthogonality Catastrophe

We investigate the spectroscopic response of a repulsively interacting, infinitely heavy impurity moving at constant velocity $v$ through a one-dimensional ideal Fermi gas. Using an exact functional-determinant approach, we calculate the Ramsey response and spectral function, fully accounting for many-body particle-hole excitations. We uncover a strongly nonmonotonic dependence on impurity velocity: decoherence is enhanced around the Fermi velocity, whereas sufficiently rapid motion restores a narrow, long-lived polaron resonance. A long-time wave-packet analysis yields analytical expressions for the polaron energy and decay rate over the full velocity range and quantitatively captures the numerical results. At high velocity, the polaron energy approaches the mean-field value, the decay rate vanishes as $1/v$, and the spectral weight approaches unity. Thus, rapid prescribed motion provides a dynamical route to suppressing the orthogonality catastrophe and restoring polaron coherence even for an infinitely heavy impurity, where recoil is entirely absent.

cond-mat.quant-gas↗
arXiv2026

Sound waves in a backreaction-affected analogue spacetime: acoustic metric, mass, and correlations in Bose-Einstein condensates

Analogue gravity treats sound as a field on an effective spacetime set by the background flow, but quantum fluctuations feed back on this background. Whether a condensate modified by such backreaction still defines a spacetime for the quantum field remains open. Using a number-conserving expansion of a Bose-Einstein condensate, we show that in the sound-wave and eikonal approximations the first-order phase fluctuation propagates on an acoustic metric of the backreaction-corrected condensate and acquires a spacetime-dependent mass that cannot be absorbed into the metric. For a finite, quasi-one-dimensional gas after an interaction quench, backreaction enhances the equal-point phase correlation by about $10\%$ in the bulk and up to $20\%$ near the walls while the depletion remains below $2\%$; the bulk enhancement survives finite imaging resolution.

cond-mat.quant-gas↗