Abstract
Periodic driving has emerged as a powerful tool in the quest to engineer new and exotic quantum phases. While driven many-body systems are generically expected to absorb energy indefinitely and reach an infinite-temperature state, the rate of heating can be exponentially suppressed when the drive frequency is large compared to the local energy scales of the system—leading to long-lived “prethermal” regimes. In this work, we experimentally study a bosonic cloud of ultracold atoms in a driven optical lattice and identify such a prethermal regime in the Bose-Hubbard model. By measuring the energy absorption of the cloud as the driving frequency is increased, we observe an exponential-in-frequency reduction of the heating rate persisting over more than 2 orders of magnitude. The tunability of the lattice potentials allows us to explore one- and two-dimensional systems in a range of different interacting regimes. Alongside the exponential decrease, the dependence of the heating rate on the frequency displays features characteristic of the phase diagram of the Bose-Hubbard model, whose understanding is additionally supported by numerical simulations in one dimension. Our results show experimental evidence of the phenomenon of Floquet prethermalization and provide insight into the characterization of heating for driven bosonic systems.
3 More- Received 20 January 2020
- Revised 31 March 2020
- Accepted 17 April 2020
DOI:https://doi.org/10.1103/PhysRevX.10.021044
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Viewpoint
Postponing Heat Death in Periodically Driven Systems
Published 27 May 2020
An exponential suppression of heating has been observed in a periodically driven optical lattice, opening up an opportunity to engineer new states of matter.
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Popular Summary
Quantum systems subject to periodic driving can reveal new properties and phenomena that have no counterparts in the undriven setting. However, a major obstacle toward this goal is the absorption of energy from the drive, which leads to heating. Two main strategies have emerged to sidestep this problem. One is the addition of strong disorder to the system, which can prevent thermalization. Another is driving the system at high frequency, which is predicted to significantly delay (though not prevent) the onset of heating, enabling a phenomenon called “prethermalization.” Theory predicts that this prethermal timescale should grow exponentially as the drive frequency increases. Here, we give the first experimental demonstration of this prediction in a system of bosons by measuring its heating dynamics over a range of drive frequencies and interaction parameters.
In our experiment, we prepare systems of bosonic atoms in 1D and 2D optical lattices. We drive the system by periodically modulating the lattice depth, and we use an atom-resolved microscopy technique to sensitively extract the temperature of the system. This allows us to demonstrate a suppression of the heating rate by as much as 2 orders of magnitude. We additionally observe spectral features characteristic of the underlying phases, which we understand with the help of numerical simulations.
Our work sheds light on the microscopic heating processes in quantum many-body systems and opens the door to the development of new exotic phases of matter out of thermal equilibrium.