Quantum phases in an asymmetric double-well optical lattice

Saurabh Paul, Eite Tiesinga

Nathan E. Lundblad, P. Lee, Ben Brown +4 more

Ippei Danshita, JAMES E. JUN. WILLIAMS, Carlos A. R. Sá de Melo +1 more

Qi Zhou, J. V. Porto, S. Das Sarma

We show theoretically that interaction effects in a double-well optical lattice can induce condensates in an excited band. For a symmetric double-well lattice, bosons condense into the bottom of the excited band at the edge of the Brillouin zone if the chemical potential is above a critical value. For an asymmetric lattice, a condensate with zero momentum is automatically induced in the excited band by the condensate in the lowest band. This is due to a combined effect of interaction and lattice potential, which reduces the band gap and breaks the inversion symmetry. Our work can be generalized to a superlattice composed of multiple-well potentials at each lattice site, where condensates can be induced in even higher bands.

Sara Bergkvist, Anders Rosengren, Robert Saers +3 more

YUANQing-Xin, DINGGuo-Hui

We investigate the phenomena of symmetry breaking and phase transition in the ground state of BoseEinstein condensates (BECs) trapped in a double square well and in an optical lattice well, respectively. By using standing-wave expansion method, we present symmetric and asymmetric ground state solutions of nonlinear Schrodinger equation (NLSE) with a symmetric double square well potential for attractive nonlinearity. In particular, we study the ground state wave function's properties by changing the depth of potential and atomic interactions (here we restrict ourselves to the attractive regime). By using the Fourier grid Hamiltonian method, we also reveal a phase transition of BECs trapped in one-dimensional optical lattice potential.