Metal-insulator-superconductor transition of spin-3/2 atoms on optical lattices

Abstract

We use a slave-rotor approach within a mean-field theory to study the competition of metallic, Mott-insulating, and superconducting phases of spin-3/2 fermions subjected to a periodic optical lattice potential. In addition to the metallic, the Mott-insulating, and the superconducting phases that are associated with the gauge symmetry breaking of the spinon field, we identify a novel emerging superconducting phase that breaks both roton and spinon field gauge symmetries. This novel superconducting phase emerges as a result of the competition between spin-0 singlet and spin-2 quintet interaction channels naturally available for spin-3/2 systems. The two superconducting phases can be distinguished from each other by quasiparticle weight. We further discuss the properties of these phases for both two-dimensional square and three-dimensional cubic lattices at zero and finite temperatures.

Collective excitations of a general spin-3/2 Fermi gas

“…The energy spectra of excitation modes are determined from the poles of these particle-hole propagators. From equations ( 12) and ( 14), we see that the longitudinal spindensity fluctuation propagator and charge-density fluctuation propagator have the same pole equations as in equation (17). Therefore, the energy spectra of density waves and longitudinal spin waves are indistinguishable under the RPA.…”

“…The former system usually satisfies the SP(N) or SU(N) symmetries, while the latter can be mapped into more general pseudo-spin models with lower symmetries by precisely controlling interaction parameters, atomic species, and particle numbers. Though enormous research works have been dedicated to exploring exotic quantum phases [10][11][12][13][14][15][16][17] and spin-mixing dynamics [18][19][20][21][22] in the large-spin Fermi gas, normal Fermi-liquid behaviors of such a system are among the most fundamental topics of interest. Based on the Landau Fermi-liquid theory, ground-state properties and lowenergy single-particle excitations of the SP(N) or SU(N) Fermi * Author to whom any correspondence should be addressed.…”

Asymptotic behavior of correlation functions of one-dimensional polar-molecules on optical lattices

“…While most variational approaches are valid only at zero temperature, the mean-field theories are unable to capture quantum fluctuations. However, slave particle theories are valid at both zero and finite temperatures and capable of capturing quantum fluctuations [44][45][46][47][48]. Further, it has been shown that slaveparticle approaches are equivalent to a statistically-consistent Gutzwiller approximation [49].…”

Effective spin-2 quasi-particles at linear dispersive five-fold degenerate points with tunable topological Chern numbers

“…As for spin-3/2, the massive relativistic spin-3/2 quasiparticle has been realized in condensed matter systems [50]. Moreover, it has been reported that superconductivity has been found in spin-3/2 topological semimetals [51][52] and optical lattices [53]. However, quasiparticles with high spin-2 are rarely studied.…”