Unusual behavior of sound velocity of a Bose gas in an optical superlattice at quasi-one-dimension

Abstract

A Bose gas trapped in a one-dimensional optical superlattice has emerged as a novel superfluid characterized by tunable lattice topologies and tailored band structures. In this work, we focus on the propagation of sound in such a novel system and have found new features on sound velocity, which arises from the interplay between the two lattices with different periodicity and is not present in the case of a condensate in a monochromatic optical lattice. Particularly, this is the first time that the sound velocity is found to first increase and then decrease as the superlattice strength increases even at one dimension. Such unusual behavior can be analytically understood in terms of the competition between the decreasing compressibility and the increasing effective mass due to the increasing superlattice strength. This result suggests a new route to engineer the sound velocity by manipulating the superlattice's parameters. All the calculations based on the mean-field theory are justified by checking the exponent γ of the off-diagonal one-body density matrix that is much smaller than 1. Finally, the conditions for possible experimental realization of our scenario are also discussed.

Effects of shape and dopant on structural, optical absorption, Raman, and vibrational properties of silver and copper quantum clusters: A density functional theory study

“…Bae et al [29] predicted that the absorption peak maximum red shifts as the cluster enlarges and blue shifts as the shape of the cluster changes from octahedron to icosahedron (Ih). In our previous investigations, we calculated the structural and optical properties of 7-, 8-, 13-, and 55-atom Ag-Cu [30][31][32][33][34][35][36] and the transition-metal-doped Ag chains. [37] According to Weissker's reports, [28] as the size becomes smaller, the number of possible symmetries becomes larger.…”

Probing the flat band of optically trapped spin-orbital-coupled Bose gases using Bragg spectroscopy

“…[29][30][31]). The presence of flat band is manifest to the eye (see Fig.2 (b1), (c1) and (d1)), as compared to an ordinary band (see Fig.2 (a1)).…”

“…From the dynamic structure factor, the excitation spectrum can then be extracted [30,31,33]. Let us calculate the excitation spectrum and the dynamic structure factor S(q, ω) of the model system for various band structures, from an ordinary band to a perfect flat band.…”

“…( 1) with fixed interaction parameter c (detailed numerical method can be found in Ref. [29][30][31]). The presence of flat band is manifest to the eye (see Fig.…”

“…with |0 (|e ) being the ground (excited) state having the energy E g (E e ). From the dynamic structure factor, the excitation spectrum can then be extracted [30,31,33].…”