Many-Body Non-Hermitian Skin Effect for Multipoles

TL;DR

This paper explores the non-Hermitian skin effect in one-dimensional systems with conserved multipole moments, revealing new boundary charge localization patterns and their impact on quantum dynamics and entanglement.

Contribution

It demonstrates that the non-Hermitian skin effect extends to systems conserving higher multipole moments, leading to novel boundary charge configurations and dynamical behaviors.

Findings

Charges localize at both boundaries in dipole-conserving systems.

Long-time steady states exhibit Fock-space localization.

Entanglement entropy follows an area-law scaling.

Abstract

In this work, we investigate the fate of the non-Hermitian skin effect in one-dimensional systems that conserve the dipole moment and higher moments of an associated global $\text{U}(1)$ charge. Motivated by field theoretical arguments and lattice model calculations, we demonstrate that the key feature of the non-Hermitian skin effect for $m$-pole conserving systems is the generation of an $(m+1)$th multipole moment. For example, in contrast to the conventional skin effect where charges are anomalously localized at one boundary, the dipole-conserving skin effect results in charges localized at both boundaries, in a configuration that generates an extremal quadrupole moment. In addition, we explore the dynamical consequences of the $m$-pole skin effect, focusing on charge and entanglement propagation. Both numerically and analytically, we provide evidence that long-time steady-states have Fock-space localization and an area-law scaling of entanglement entropy, which serve as quantum indicators of the skin effect.