Tiny Bubbles in my BEC

Conference · Wed Aug 01 04:00:00 EDT 2012

OSTI ID:1048693

Blinova, Alina A ^[1]

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1. Los Alamos National Laboratory

Ultracold atomic gases provide a unique way for exploring many-body quantum phenomena that are inaccessible to conventional low-temperature experiments. Nearly two decades ago the Bose-Einstein condensate (BEC) - an ultracold gas of bosons in which almost all bosons occupy the same single-particle state - became experimentally feasible. Because a BEC exhibits superfluid properties, it can provide insights into the behavior of low-temperature helium liquids. We describe the case of a single distinguishable atom (an impurity) embedded in a BEC and strongly coupled to the BEC bosons. Depending on the strength of impurity-boson and boson-boson interactions, the impurity self-localizes into two fundamentally distinct regimes. The impurity atom can behave as a tightly localized 'polaron,' akin to an electron in a dielectric crystal, or as a 'bubble,' an analog to an electron bubble in superfluid helium. We obtain the ground state wavefunctions of the impurity and BEC by numerically solving the two coupled Gross-Pitaevskii equations that characterize the system. We employ the methods of imaginary time propagation and conjugate gradient descent. By appropriately varying the impurity-boson and boson-boson interaction strengths, we focus on the polaron to bubble crossover. Our results confirm analytical predictions for the polaron limit and uncover properties of the bubble regime. With these results we characterize the polaron to bubble crossover. We also summarize our findings in a phase diagram of the BEC-impurity system, which can be used as a guide in future experiments.

• Research Organization: Los Alamos National Laboratory (LANL)
• Sponsoring Organization: LDRD
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1048693
• Report Number(s): LA-UR-12-23724
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATOMS
BOSONS
BUBBLES
CONDENSATES
DIELECTRIC MATERIALS
ELECTRONS
GASES
GROUND STATES
HELIUM
LANL
PHASE DIAGRAMS
POLARONS