Group Seminar at LMU and Zoom: Emergence of non-Hermitian dynamics in a quantum gas leading to a self-driven topological pump

April 18, 2023

Alexander Baumgärtner, ETH Zürich
Group Seminar at LMU and zoom
Tuesday, April 18th, 09:00am (MEZ)


The time evolution of a driven quantum system can be strongly affected by dissipation. Although this mainly implies that the system relaxes to a steady state, in some cases it can lead to the appearance of new phases and trigger emergent dynamics. In our experiment, we study a Bose-Einstein condensate dispersively coupled to a high finesse optical resonator. The cavity is populated by scattering photons from a transverse drive illuminating the atoms. The sum of the drive and the self-consistent intracavity field provides a topological band structure. When the dissipative and coherent timescales are comparable, we find a regime of persistent oscillations where the cavity field does not reach a steady state: The emergence of an exceptional point. In this regime the atoms experience a potential that periodically deforms itself, even in the absence of an external time-dependent drive. Consequently, the dynamic lattice triggers topological pumping [1]. We show complementary measurements of the light field and of the atomic transport, proving the connection between the non-stationarity and the topological pumping and further investigate the emergence of the dynamics with various spectroscopic techniques.

[1] Dreon D, Baumgärtner A, Li X, Hertlein S, Esslinger T & Donner T: Self-oscillating pump in a topological dissipative atom–cavity system. Nature 608, 494–498 (2022)

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