Biaxial spin-nematic phase of two-dimensional disordered rotor models andS=1bosons in optical lattices

Abstract

We show that the ground state of disordered rotor models with quadrupolar interactions can exhibit biaxial nematic ordering in the disorder-averaged sense. We present a mean-field analysis of the model and demonstrate that the biaxial phase is stable against small quantum fluctuations. We point out the possibility of experimental realization of such rotor models using ultracold spin-one Bose atoms in a spin-dependent and disordered optical lattice in the limit of a large number of atoms per site and also suggest an imaging experiment to detect the biaxial nematicity in such systems.

Stability of supercurrents in a superfluid phase of spin-1 bosons in an optical lattice

“…Although we set U 2 /U 0 optimal values for validity of the theory that is not realistic in the present experimental status, the obtained results may be applicable to 23 Na with U 2 /U 0 = 0.04. The first-order phase transition dominates the larger part of the phase boundary and the region of the metastable SF phase in the phase diagram gets larger for smaller U 2 /U 0 [14,17].…”

“…The first-order phase transition dominates the larger part of the phase boundary and the region of the metastable SF phase in the phase diagram gets larger for smaller U 2 /U 0 [14,17]. The effect of the first-order phase transition, therefore, may be remarkable and easy to study experimentally for 23 Na.…”

“…U 2 /U 0 is fixed for each atomic species. For example, U 2 /U 0 = 0.04 for 23 Na [11]. In this paper, we set U 2 /U 0 optimal values for validity of the theory.…”

“…The rich structure of the phase diagram that arises from the interplay between strong correlations and spin degrees of freedom has been a main focus of intense theoretical studies. It exhibits many interesting features including the parity effect of the MI phase [10][11][12][13], the first-order SF-MI transition [14][15][16][17], and the spin-nematic order in the MI phase [12,[18][19][20][21][22][23][24][25][26]. On the other hand, recent progress of experimental studies have made possible to observe the signature of the first-order phase transition [27] and quantum critical dynamics [28] in this system.…”

Generating an effective magnetic lattice for ultracold atoms

“…With spin-dependent OLs, atomic internal degrees of freedom such as its spin or pseudo-spin (group of internal states), are coupled to its spatial degrees of freedom. This can give rise to interesting phenomena [9][10][11][12][13][14][15][16][17][18] absent in spin-independent lattices. For example, attractive Fermi gases in 1D lattices support three-body bound states with only two-body interactions when the tunneling rates are spin-dependent [19].…”