Quantum phases of spinful Fermi gases in optical cavities

Abstract

We explore the quantum phases emerging from the interplay between spin and motional degrees of freedom of a one-dimensional quantum fluid of spinful fermionic atoms, effectively interacting via a photon-mediating mechanism with tunable sign and strength g, as it can be realized in present-day experiments with optical cavities. We find the emergence, in the very same system, of spin-and atomic-density wave ordering, accompanied by the occurrence of superfluidity for g > 0, while cavity photons are seen to drive strong correlations at all g values, with fermionic character for g > 0, and bosonic character for g < 0. Due to the long-range nature of interactions, to infer these results we combine mean-field and exact diagonalization methods supported by bosonization analysis.

Cavity-Mediated Unconventional Pairing in Ultracold Fermionic Atoms

“…Since the longrange (in fact, in our setup it is infinite-range) nature of the cavity-mediated interaction implies that any atom will always interact with a large number of other atoms, this approach is well justified. This was found to be the case even in one dimension in [36] using bosonisation methods. We decouple the electron interactions using the mean fields…”

“…Artificial magnetic fields can be induced to create distinct topological phases [27][28][29]. Most importantly, various types of cavity-mediated interactions could give rise to a plethora of many-body phases [30][31][32][33][34][35][36][37][38], including superfluid and charge density states, and even more exotic phases with no direct analog in condensed matter systems. All these developments render ultracold fermionic atoms natural candidates to explore exotic physics, such as topological phases [39][40][41], which would be more difficult to observe in condensed matter.…”

“…Previous theoretical works describing cavity-mediated interactions of fermionic atoms had focused on one-dimensional lattices [33][34][35][36]. In [36], the spin states were energetically separated, such that the cavity coupling was shown to induce either singlet superfluidity or spin-density order. Camacho-Guardian et al [35] investigate the same effective interaction mechanism as considered here.…”

Cavity-induced emergent topological spin textures in a Bose–Einstein condensate

“…These systems exhibit many more interesting phenomena, including the emergence of synthetic strong magnetic fields and spin-orbit coupling [46][47][48][49], disorder-driven density and spin self-ordering [50], topological states [51,52], and a variety of magnetic Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. orders [53,54]. Very recently, first experimental implementations showing spin self-ordering in a spin-1 BEC in a standing wave cavity were realized [55,56].…”

Antiferromagnetic self-ordering of a Fermi gas in a ring cavity

“…With the prediction of new intriguing phenomena such as Umklapp superradiance [26,27], topologically protected edge states [28,29], superconducting pairing [30,31], artificial dynamic gauge fields [20], unconventional momentum correlations and quantum phases in multiple dimensions [32][33][34][35], implementations of fermionic systems coupled to cavity fields have gained more attention recently. In the present article, we propose the realization of density and spin self-ordering for a transversely driven multi-level Fermi gas coupled to a pair of counterpropagating degenerate modes of a ring cavity as depicted in figure 1 [36][37][38][39][40][41][42].…”