Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 69: Other Low Temperature Topics: Cold Atomic Gases
TT 69.7: Vortrag
Mittwoch, 18. März 2015, 16:30–16:45, A 053
Directed motion of doublons and holes in periodically driven Mott insulators — •Maximilian Genske and Achim Rosch — Institut für Theoretische Physik, Universität zu Köln, D-50937 Cologne, Germany
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 directions. 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 ω and the external force g are commensurate, n0 g = m0 ω, with n0/2,m0 ∈ Z. Ultimately, increasing the density of excitations leads to a breakdown of the one-particle picture. As an outlook, we thus discuss how interaction effects can be described by Floquet-Boltzmann equations.