Group Seminar at LMU: Chiral orbital order of interacting bosons without higher bands

May 02, 2023

Prof. Marco DiLiberto, University of Padova
Group Seminar at LMU seminar room H107 and zoom
Tuesday, May 2nd, 09:00am (MEZ)


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 on-site 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.

Marco Di Liberto and Nathan Goldman
Phys. Rev. Research 5, 023064 – Published 27 April 2023

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