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5. July 2023 17:00

Supersolid Phases of Dipolar and Spin-Orbit Coupled Bosons in Optical Lattices

Prof. Carlos Sa de Melo
School of Physics, Georgia Institute of Technology, Atlanta

I begin this talk by reviewing the existence of supersolid and melted supersolid phases (hexatic superfluids) in two-dimensional continuum dipolar boson systems [1]. Immediately after that, I discuss the emergence of supersolid phases of dipolar and spin-orbit coupled bosons in optical lattices. For dipolar systems, we show that the ground state phase diagram is very sensitive to the direction of an externally applied field with respect to the normal to the plane of a two-dimensional square optical lattice, and that supersolids are stabilized by dipolar interactions [2]. We find that the phase diagram, at high filling factors, is very rich with various supersolid (e.g., checkerboard and striped) phases emerging out of superfluid regions [2]. For spin-orbit coupled systems in two-dimensional square optical lattices, we show that the competition between the optical lattice period and the spin-orbit coupling length – which can be made comparable in experiments – along with spin hybridization induced by a transverse field (i.e., Rabi coupling) and local interparticle interactions, create a rich variety of quantum phases including uniform and phase separated superfluids and supersolids [3]. Finally, I present recent results describing the existence of a Devil’s staircase of supersolid phases, when the spin-orbit coupling momentum transfer is not aligned with the principal axis of the square lattice [4].

[1] “Hexatic, Wigner Crystal, and Superfluid Phases of Dipolar Bosons”, K. Mitra, C. J. Williams, and C. A. R. Sá de Melo, arXiv:0903.4665v1 (26 Mar 2009).

[2] “Stability of Superfluid and Supersolid Phases of Dipolar Bosons in Optical Lattices”, I. Danshita and C. A. R. Sá de Melo, Phys. Rev. Lett. 103, 225301 (2009).

[3] “Quantum Phases of Two-Component Bosons with Spin-Orbit Coupling in Optical Lattices”, D. Yamamoto, I. B. Spielman, and C. A. R. Sá de Melo, Phys. Rev. A 96, 061603(R) (2017).

[4] “Supersolid Devil’s Staircases of Spin-Orbit-Coupled Bosons in Optical Lattices”, D. Yamamoto, K. Bannai, N. Furukawa, and C. A. R. Sá de Melo, Phy. Rev. Res. 4, L032023 (2022)