Itinerant ferromagnetism of two-dimensional repulsive fermions with Rabi coupling

Year: 2017

Authors: Penna V., Salasnich L.

Autors Affiliation: Politecn Torino, Dipartimento Fis, Corso Duca Abruzzi 24, I-10129 Turin, Italy;‎ CNISM, Corso Duca Abruzzi 24, I-10129 Turin, Italy; Univ Padua, Dipartimento Fis & Astron Galileo Galilei, Via Marzolo 8, I-35131 Padua, Italy; Univ Padua, CNISM, Via Marzolo 8, I-35131 Padua, Italy;‎ CNR, INO, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy

Abstract: We study a two-dimensional fermionic cloud of repulsive alkali-metal atoms characterized by two hyperfine states which are Rabi coupled. Within a variational Hartree-Fock scheme, we calculate analytically the ground-state energy of the system. Then we determine the conditions under which there is a quantum phase transition with spontaneous symmetry breaking from a spin-balanced configuration to a spin-polarized one, an effect known as itinerant ferromagnetism. Interestingly, we find that the transition appears when the interaction energy per particle exceedes both the kinetic energy per particle and the Rabi coupling energy. The itinerant ferromagnetism of the polarized phase is analyzed, obtaining the population imbalance as a function of interaction strength, Rabi coupling, and number density. Finally, the inclusion of a external harmonic confinement is investigated by adopting the local density approximation. We predict that a single atomic cloud can display population imbalance near the center of the trap and a fully balanced configuration at the periphery.


Volume: 19      Pages from: 043018-1  to: 043018-9

KeyWords: fermions; two-dimensional systems; Rabi coupling; Stoner instability; itinerant ferromagnetism
DOI: 10.1088/1367-2630/aa69fd

Citations: 9
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