Controlling quantum scars and engineering subharmonic responses with a two frequency drive

TL;DR

This paper shows how a two-frequency drive can control quantum many-body scars, induce non-equilibrium phases, and generate subharmonic responses, offering a versatile method for quantum state engineering.

Contribution

It introduces a systematic approach using two-frequency driving to manipulate quantum scars, prethermal phases, and subharmonic responses in quantum many-body systems.

Findings

Long-lived scarred dynamics at small integer frequency ratios

Non-monotonic transitions between ergodic and non-ergodic behavior

Engineering of fractional subharmonic responses

Abstract

We demonstrate that a continuous two frequency drive is a versatile and robust protocol to control the lifetime of quantum many body scars and to engineer non-equilibrium phases of driven quantum matter. By modulating the frequency ratio $c$ (any rational number), we systematically explore prethermal features across a broad frequency range. For small integer values of $c$, we observe ergodicity breaking even at moderately low frequencies, signaling long-lived scarred dynamics. By continuously increasing $c$, one can generate non-monotonic transitions between ergodic and non-ergodic dynamics. These observations are consistent with the predictions of an effective Floquet Hamiltonian based approach. Furthermore, we exploit this tunability to engineer fractional subharmonic responses, highlighting the potential of two-frequency driving as a theoretical platform for controlling scars, prethermalization, and time crystal-like behavior.