Atomtronics with a spin: Statistics of spin transport and nonequilibrium orthogonality catastrophe in cold quantum gases

Jhih-Shih You, Richard Schmidt, Dmitri A. Ivanov, Michael Knap, and Eugene Demler
Phys. Rev. B 99, 214505 – Published 13 June 2019

Abstract

We propose to investigate the full counting statistics of nonequilibrium spin transport with an ultracold atomic quantum gas. The setup makes use of the spin control available in atomic systems to generate spin transport induced by an impurity atom immersed in a spin-imbalanced two-component Fermi gas. In contrast to solid-state realizations, in ultracold atoms spin relaxation and the decoherence from external sources is largely suppressed. As a consequence, once the spin current is turned off by manipulating the internal spin degrees of freedom of the Fermi system, the nonequilibrium spin population remains constant. Thus one can directly count the number of spins in each reservoir to investigate the full counting statistics of spin flips, which is notoriously challenging in solid-state devices. Moreover, using Ramsey interferometry, the dynamical impurity response can be measured. Since the impurity interacts with a many-body environment that is out of equilibrium, our setup provides a way to realize the nonequilibrium orthogonality catastrophe. Here, even for spin reservoirs initially prepared in a zero-temperature state, the Ramsey response exhibits an exponential decay, which is in contrast to the conventional power-law decay of Anderson's orthogonality catastrophe. By mapping our system to a multistep Fermi sea, we are able to derive analytical expressions for the impurity response at late times. This allows us to reveal an intimate connection of the decay rate of the Ramsey contrast and the full counting statistics of spin flips.

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  • Received 13 December 2018
  • Revised 23 May 2019

DOI:https://doi.org/10.1103/PhysRevB.99.214505

©2019 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied PhysicsStatistical Physics & Thermodynamics

Authors & Affiliations

Jhih-Shih You1,2, Richard Schmidt3,4, Dmitri A. Ivanov5, Michael Knap4,6, and Eugene Demler1

  • 1Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
  • 2Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
  • 3Max Planck Institute of Quantum Optics, Hans-Kopfermann-Str. 1, 85748 Garching, Germany
  • 4Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, D-80799 München, Germany
  • 5Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
  • 6Department of Physics and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany

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Issue

Vol. 99, Iss. 21 — 1 June 2019

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