Many-Body Spin Echo

TL;DR

This paper predicts a universal many-body spin echo phenomenon in interacting quantum systems, characterized by a coherent revival of transition probabilities unaffected by interactions or spin-orbit coupling.

Contribution

It introduces a universal many-body spin echo effect with analytical predictions and numerical validation, highlighting its independence from interaction strength and its dependence on particle and spin flip relations.

Findings

The echo signal has a universal shape regardless of interaction strength.

The amplitude and sign depend only on particle and spin flip combinatorics.

Numerical simulations confirm the analytical predictions and the role of anti-unitary symmetries.

Abstract

We predict a universal echo phenomenon present in the time evolution of many-body states of interacting quantum systems described by Fermi-Hubbard models. It consists of the coherent revival of transition probabilities echoing a sudden flip of the spins that, contrary to its single-particle (Hahn) version, is not dephased by interactions or spin-orbit coupling. The many-body spin echo signal has a universal shape independent of the interaction strength, and an amplitude and sign depending only on combinatorial relations between the number of particles and the number of applied spin flips. Our analytical predictions, based on semiclassical interfering amplitudes in Fock space associated with chaotic mean-field solutions, are tested against extensive numerical simulations confirming that the coherent origin of the echo lies in the existence of anti-unitary symmetries.