Speaker: Professor Uli Zülicke
Affiliation: Victoria University of Wellington


The two-dimensional spin-imbalanced Fermi gas subject to s-wave pairing and spin-orbit coupling is considered a promising platform for realizing a topological chiral-p-wave superfluid [1]. In the BCS limit of s-wave pairing, i.e., when Cooper pairs are only weakly bound, the system enters the topological phase via a second-order transition driven by increasing the Zeeman spin-splitting energy [2]. For larger Cooper-pair bound-state energies, the system undergoes the BCS–BEC crossover, in the course of which the topological transition becomes first-order [3]. As a result, topological and nontopological superfluids coexist in an extended region of phase space spanned by the two-particle s-wave bound-state energy and the Zeeman energy.

We have investigated the topological-superfluid – nontopological-superfluid coexistence region theoretically using a zero-temperature mean-field approach, revealing intriguing physical properties [4]. The internal interface between topological and nontopological parts of the system is found to host unconventional Andreev bound states [5] — including a Majorana mode — whose properties can be tailored by tuning parameters that are routinely accessible in ultracold-atom experiments. Our results thus extend current understanding of spin-imbalanced superfluid Fermi systems and may inform experimental efforts aimed at realizing Majorana quasiparticles.


[1] M. Sato, Y. Ando, Rep. Prog. Phys. 80, 076501 (2017).

[2] J. D. Sau, R. M. Lutchyn, S. Tewari, S. Das Sarma, Phys. Rev. Lett. 104, 040502 (2010); J. Alicea, Phys. Rev. B 81, 125318 (2010).

[3] K. Thompson, J. Brand, U. Zülicke, Phys. Rev. A 101, 013613 (2020).

[4] K. Thompson, U. Zülicke, J. Brand, Phys. Rev. Research 4, 043201 (2021).

[5] K. Thompson, J. Brand, U. Zülicke, SciPost Phys. 14, 115 (2023).

About Australia - New Zealand Cold Atom Seminars

This new initiative hosts a seminar once a month for the Australia – New Zealand cold atom research community.  The purpose is to encourage and facilitate ongoing discussions and collaboration in the local community.  Talks should be less than 40 minutes in length to allow ample time for questions and discussion.

Seminars will be held on the last Friday of the month (except for December) at 1pm Melbourne time (which is normally 3pm New Zealand time).  While the primary format is online via Zoom, various institutions will host the seminar in local seminar rooms.  The Zoom link is https://uqz.zoom.us/j/88604569495

You can sign up for announcements for the seminars at this webpage:

Seminars are recorded, and past seminars can be accessed from this web page.

Contact Matthew Davis mdavis@physics.uq.edu.au for further information.



Zoom: https://uqz.zoom.us/j/88604569495