arXiv:1411.5593 · Physical Review A

Metastable Bose-Einstein condensation in a strongly correlated optical lattice

David C. McKay, Ushnish Ray, Stefan S. Natu, Philip Russ, David M. Ceperley, Brian DeMarco

Published Feb 24, 2015• 10 citations

Abstract

The Bose-condensed fraction of a cold gas loaded into a three-dimensional optical lattice is studied both experimentally and theoretically, and the strong disagreement between experiment and theory at high temperatures indicates that the system may not reach equilibrium in this regime and that the condensate is metastable.

DOI: 10.1103/physreva.91.023625

Related papers

Bose-Einstein condensates in optical lattices : the superfluid to Mott insulator phase transition

Jongchul Mun

87Rb Bose Einstein Condensate in 3D optical lattice was studied in the regime of weak interaction(the superfluid phase) and strong interaction(the Mott insulating phase). The stability of superfluid currents was studied using a moving optical lattice. The critical momentum for stable superfluid current varies from 0.5 recoil momentum (shallow lattice) to 0 (the Mott insulator) as the system reaches the Mott insulator transition. The phase diagram for the disappearance of superfluidity was studied as a function of momentum and lattice depth. Our phase diagram boundary ex-trapolates to the critical lattice depth for the superfluid-to-MI transition. When a one-dimensional gas was loaded into a moving optical lattice a sudden broadening of the transition between stable and unstable phases was observed. A new auxiliary vacuum chamber, which is called the science chamber, was de-signed and installed to improve optical lattice experimental performance and imaging resolution power. Atoms are transported from the main chamber to the science cham-ber. By further evaporation cooling, BECs with N- 2-3 x 104 atoms are produced

Jan 1, 20083 citations

BOSONS IN OPTICAL LATTICES

S. L. Rolston

The advent of coherent matter waves in the form of Bose-Einstein condensates, coupled with periodic potentials in the form of optical lattices, has established a new area of research on the boundary between atomic and condensed matter physics. This article is a brief review of the recent experimental progress in the area of degenerate Bose gases loaded into optical lattices, including strongly correlated systems and the role of dimensionality. Future prospects will also be outlined.

International Journal of Modern Physics BJul 30, 20063 citations

BOSE-EINSTEIN CONDENSATES IN LOW DIMENSIONAL OPTICAL LATTICES: NOVEL QUANTUM PHASES AND NON-EQUILIBRIUM PHENOMENA

Sayan Choudhury

Cold atoms trapped in optical lattices (crystals of light) provide a pristine platform for exploring quantum many body physics. Motivated by several recent experiments, this thesis examines the equilibrium and non-equilibrium dynamics of a Bose-Einstein condensate (BEC) loaded in a low dimensional optical lattice in order to realize novel quantum phases. There are two main research directions in this thesis. The first one involves the possibility that exotic order spontaneously forms when two-component bosons are trapped in a honeycomb lattice. My studies on this theme is motivated by the observation of a “twisted superfluid” state in Prof. Klaus Sengstock’s group at Hamburg (Soltan-Panahi et al., Nat. Phys. 8, 71 (2012)). A twisted superfluid involves Bose-Einstein condensation into a state whose order parameter has a spatially varying phase. In chapter 3, I study the stability of a Bose-Einstein condensate towards forming a twisted superfluid within the framework of mean field theory. Despite a exhaustive numerical search I do not find a parameter regime with a twisted superfluid. This search involved all experimentally relevant parameter regimes and therefore mean field theory predicted that the experimentalists should not observe a twisted superfluid. I conclude that the experimental observations were either a manifestation of counter superfluidity or due to interactions during time-of-flight. Subsequent experiments showed that the observations were an artifact of the measurement process. The second research direction in this thesis is an exploration of the stability of periodically driven quantum systems (also known as Floquet systems). Floquet systems can be used to realize exotic non-equilibrium quantum phases which do not have a counterpart in static systems. However, the driving can cause these systems to heat up which presents a major obstacle to creating exotic states. To explore this issue in a concrete example, I model an experiment (Parker, Ha, and Chin, Nat. Phys. 9, 769 (2013)) where a Bose-Einstein condensate loaded in an optical lattice is subjected to periodic shaking. I investigate the stability of this Floquet BEC to interactions. This research direction consists of 3 studies. In chapter 4, I first do this analysis for a purely one-dimensional system and identify a large parameter regime where the BEC is stable. In the next two chapters, I go beyond 1D and consider the role of transverse degrees of freedom. This is because the shaken lattice experiments that I model involves a 1D array of pancakes. I find that this geometry leads to much more dissipation than a purely 1D system. This extra dissipation arises because interactions can transfer energy between different directions. In chapter 5, I consider the extreme case where there is no transverse confinement. I find that in the absence of transverse confinement, a one-dimensional Floquet BEC is generically unstable. Finally, in chapter 6, I consider harmonic transverse confinement modeling the crossover between chapters 4 and 5. I find that as the transverse confinement is made stronger, the atom loss rate initially increases, but beyond a critical transverse confinement, the atom loss disappears due to unavailability of phase space for scattering. I also predict that if the transverse confinement is tuned to the vicinity of certain magic values, the heating rate exhibits a sharp drop. I perform similar analyses for a shaken square lattice and find that generically a low-dimensional Floquet BEC can be stabilized by suitably designing the transverse confinement.

Jan 1, 20170 citations

Bose–Einstein condensation in one-dimensional optical lattices: Bogoliubov’s approximation and beyond

Mohamed K. Al-Sugheir, Mufeed A. Awawdeh, H. B. Ghassib +1 more

Bose–Einstein condensation in a finite one-dimensional atomic Bose gas trapped in an optical lattice is studied within Bogoliubov’s approximation and then beyond this approximation, within the static fluctuation approximation. A Bose–Hubbard model is used to construct the Hamiltonian of the system. The effect of the potential strength on the condensate fraction is explored at different temperatures; so is the effect of temperature on this fraction at different potential strengths. The role of the number of lattice points (the size effect) at constant number density (the filling factor) is examined; so is the effect of the number density on the condensate fraction. The results obtained are compared to other published results wherever possible.

Canadian Journal of PhysicsApr 27, 20162 citations

Temperature and degeneracy of ultra-cold bosons in optical lattices

P. B. Blakie

In the past 5 years optical lattices have emerged as a versatile new tool for engineering strongly correlated states of ultra-cold atoms. In this talk we present a theory for the thermal changes that occur during lattice loading and propose a procedure for measuring the temperature of a superfluid Bose gas in an optical lattice.

Quantum-Atom Optics Downunder (QAO)Jan 1, 20070 citations

Study of a 1D interacting quantum Bose gas

B. Laburthe-Tolra, Kenneth M. O’Hara, J. H. Huckans +4 more

The loading of a Bose-Einstein condensate into a deep two-dimensional optical lattice provides a unique way to study one-dimensional Bose gases: the strong radial confinement freezes any motion in two dimensions, and for deep enough lattices, the system can be seen as an array of independent I D tubers. For our experimental parameters, the ID gas is predicted to be in an intermediate regime between the Tonks-Girardeau and the Thomas-Fermi regimes. We performed experiments showing that some long range phase coherence is present in this regime. We investigated correlation properties of these gases by studying their collective oscillations. In addition, we investigated the ID Mott transition by adiabatically loading the 1D gases into a 1D optical lattice.

Journal de Physique IV (Proceedings)Oct 1, 20040 citations