Critical quasienergy states in driven many-body systems

TL;DR

This paper explores how driving many-body spin systems creates controllable singularities in the quasienergy spectrum, leading to observable signatures like divergences in density of states and magnetization.

Contribution

It demonstrates how external driving can engineer and control singularities in the quasienergy landscape of many-body systems, a novel approach compared to undriven models.

Findings

Logarithmic divergences at saddle points in quasienergy density

Jumps in density due to local minima in quasienergy landscape

Observable signatures in magnetization measurements

Abstract

We discuss singularities in the spectrum of driven many-body spin systems. In contrast to undriven models, the driving allows us to control the geometry of the quasienergy landscape. As a consequence, one can engineer singularities in the density of quasienergy states by tuning an external control. We show that the density of levels exhibits logarithmic divergences at the saddle points, while jumps are due to local minima of the quasienergy landscape. We discuss the characteristic signatures of these divergences in observables like the magnetization, which should be measurable with current technology.