Chiral orbital order of interacting bosons without higher bands

• DOI: 10.1103/physrevresearch.5.023064
• Publication Date: 2023-04-27T15:12:33Z
• Authors: Marco Di Liberto; Nathan Goldman
• Keywords: 0301 basic medicine; Quantum Physics; Condensed Matter - Mesoscale and Nanoscale Physics; Physique; Physics; QC1-999; FOS: Physical sciences; 03 medical and health sciences; Quantum Gases (cond-mat.quant-gas); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Condensed Matter - Quantum Gases; Quantum Physics (quant-ph); Physics - Optics; Optics (physics.optics)

Ultracold atoms loaded into higher Bloch bands provide an elegant setting for realizing many-body quantum states that spontaneously break time-reversal symmetry through the formation of chiral orbital order. The applicability of this strategy remains nonetheless limited due to the finite lifetime of atoms in high-energy bands. Here we introduce an alternative framework, suitable for bosonic gases, which builds on assembling square plaquettes pierced by a $π$-flux (half a magnetic-flux quantum). This setting is shown to be formally equivalent to an interacting bosonic gas loaded into $p$ orbitals, and we explore the consequences of the resulting chiral orbital order, both for weak and strong onsite interactions. We demonstrate the emergence of a chiral superfluid vortex lattice, exhibiting a long-lived gapped collective mode that is characterized by local chiral currents. This chiral superfluid phase is shown to undergo a phase transition to a chiral Mott insulator for sufficiently strong interactions. Our work establishes coupled $π$-flux plaquettes as a practical route for the emergence of orbital order and chiral phases of matter.<br/>4+3 pages, 4+2 figures<br/>