Directed motion of doublons and holes in periodically driven Mott insulators

TL;DR

This paper explores how periodic driving induces directed motion of doublons and holes in a bosonic Mott insulator, enabling control over excitations and transport against external forces under specific resonance conditions.

Contribution

It demonstrates an effective quantum ratchet mechanism for manipulating doublons and holes in driven Mott insulators, revealing conditions for uphill transport and excitation control.

Findings

Doublons and holes can be driven in opposite directions.

Transport occurs only when driving frequency and external force are commensurate.

Periodic driving enables manipulation of excitations in Mott insulators.

Abstract

Periodically driven systems can lead to a directed motion of particles. We investigate this ratchet effect for a bosonic Mott insulator where both a staggered hopping and a staggered local potential vary periodically in time. If driving frequencies are smaller than the interaction strength and the density of excitations is small, one obtains effectively a one-particle quantum ratchet describing the motion of doubly occupied sites (doublons) and empty sites (holes). Such a simple quantum machine can be used to manipulate the excitations of the Mott insulator. For suitably chosen parameters, for example, holes and doublons move in opposite direction. To investigate whether the periodic driving can be used to move particles "uphill", i.e., against an external force, we study the influence of a linear potential $- g x$. For long times, transport is only possible when the driving frequency $\omega$ and the external force $g$ are commensurate, $n_0 g = m_0 \omega$, with $\frac{n_0}{2},m_0 \in \mathbb{Z}$.