Localization of an inhomogeneous Bose-Einstein condensate in a moving random potential

Abstract

We study the dynamics of a harmonically trapped quasi-one-dimensional Bose-Einstein condensate subjected to a moving disorder potential of finite extent. We show that, due to the inhomogeneity of the sample, only a percentage of the atoms is localized at supersonic velocities of a random potential. We find that this percentage can be sensitively increased by introducing suitable correlations in the disorder potential such as those provided by random dimers.

Probing quantum transport by engineering correlations in a speckle potential

“…The disorder potential is pulled through the BEC with a velocity v over a distance L * . We measure the center-of-mass shift z cm and we identify the ratio of localized atoms N loc /N with the ratio z cm /L * , indeed if the whole BEC is insensible to the disorder potential then z cm = 0, while if the whole BEC is stuck on the disorder potential then z cm = L * [14].…”

“…Since we expect to observe localization for v c, c = µ/2m being the 1D speed of sound [13,14,32] with µ the chemical potential, we tune the position of the localization peak in this region and choose the value of the dimer length d to enhance the interference effects. With this purpose, we study the localized BEC fraction N loc /N as a function of v/c for the case of a RD-speckle of potential strength V dis = 0.05 ω ⊥ and different values of d, d = 0.4 cm (blue circles), d = 0.8 cm (turquoise crosses) and d = 1.2 cm (black plus signs).…”

“…[12,13] studied the transport of a homogeneous one-dimensional (1D) interacting Bose-Einstein condensate (BEC) in the presence of a moving random potential of finite extent L. They proved the presence of an Anderson localization regime by studying the transmission of the BEC through the potential and showing that it decays exponentially with L. However, in ordinary ultracold-atom experiments, BECs are trapped in a harmonic confinements and thus they are inhomogeneous. Transmission is no longer a well defined observable in such a geometry, however one can identify the presence of some localization effects by studying the time evolution of the BEC center-of-mass [14,15]. If the center-of-mass follows the moving random potential, the BEC is trapped by the random potential; it remains difficult to say if this localization is classical or induced by the interference of the scattered fluid.…”

Dynamical properties of a condensate in a moving random potential

“…On the contrary, at velocities greater than v cr , superfluidity breaks down and the interference of the scattered waves may deeply modify the fluid transport [8][9][10] unto the Anderson localization regime [11,12]. In a confined system where the density is inhomogeneous, superfluidity breaks down beforehand in the low density regions and one may observe the inhibition of the expansion [13], the dipolar mode damping [14], and the localization of a piece of the system [15]. Differently and in complementarity with [15], in this paper we focus on the dynamical evolution of the localized fraction of a cigar-shaped Bose-Einstein condensate (BEC) subject to a moving random potential.…”

“…In a confined system where the density is inhomogeneous, superfluidity breaks down beforehand in the low density regions and one may observe the inhibition of the expansion [13], the dipolar mode damping [14], and the localization of a piece of the system [15]. Differently and in complementarity with [15], in this paper we focus on the dynamical evolution of the localized fraction of a cigar-shaped Bose-Einstein condensate (BEC) subject to a moving random potential. We analyze the density and center-of-mass time-evolution of the system, comparing two types of disorder potentials characterized by different correlation functions.…”