# Physics Colloquium: Michael Kolodrubetz, "Dynamics of boundary-driven gapless quantum systems"

When |
Mar 28, 2017
from 02:00 PM to 03:00 PM |
---|---|

Where | MR418N |

Contact Name | Myriam Sarachik |

Contact Phone | 212-650-5618 |

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Tuesday, March 28

Michael Kolodrubetz, University of California, Berkeley

TITLE: Dynamics of boundary-driven gapless quantum systems

ABSTRACT:

Periodic driving, also known as Floquet driving, is one of the most powerful tools for engineering novel quantum states. In this talk, I will introduce Floquet theory and explain how drive may be used for creating not only interesting Hamiltonians, but also non-equilibrium states with no equilibrium counterpart. In generic systems, these effects compete against energy absorption from the drive, which results in uncontrolled heating. I will discuss two examples where we have been able to theoretically understand and control this heating by considering the case of a boundary drive. First, inspired by recent time-resolved ARPES experiments, I will discuss the driven surface states of a topological insulator. Instead of incoherent heating, we find that this system displays coherent bulk-surface oscillations due to non-adiabatic effects of the pump. Second, I will discuss the case of a one-dimensional boundary-driven quantum critical system, whose bulk is described a conformal field theory. I will show how we combine the analytical tools of boundary conformal field theory and Floquet theory to find a fascinating universal non-equilibrium phase diagram. Its most surprising feature is a low-frequency regime where the simple predictions of conformal field theory are modified by non-equilibrium crossing of the boundary critical point, a phenomenon known for bulk systems as Kibble-Zurek scaling. I will comment on how these ideas can be used for creating and detecting interesting quantum states and briefly highlight how they fit into the broader context of non-equilibrium quantum systems.

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The speaker is a candidate for the position of Assistant/Associate Professor of Physics.