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arXiv · 2109.14505

Optical spin transport theory of spin-1/2 topological Fermi superfluids

Hiroyuki Tajima·Yuta Sekino·Shun Uchino
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Abstract

We theoretically investigate optical (frequency-dependent) bulk spin transport properties in a spin-1/2 topological Fermi superfluid. We specifically consider a one-dimensional system with an interspin {\it p}-wave interaction, which can be realized in ultracold atom experiments. Developing the BCS-Leggett theory to describe the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) evolution and the $\mathbb{Z}_2$ topological phase transition in this system, we show how the spin transport reflects these many-body aspects. We find that the optical spin conductivity, which is a small AC response of a spin current, shows the spin gapped spectrum in the wide parameter region and the gap closes at $\mathbb{Z}_2$ topological phase transition point. Moreover, the validity of the low-energy effective model of the Majorana zero mode is discussed along the BCS-BEC evolution in connection with the scale invariance at {\it p}-wave unitarity.

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Hiroyuki Tajima, Yuta Sekino, Shun Uchino. 2021-09-29. Optical spin transport theory of spin-1/2 topological Fermi superfluids. https://doi.org/10.1103/physrevb.105.064508

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