Spontaneous symmetry breaking of Bose-Fermi mixtures in double-well potentials

Journal Article · Sat May 15 00:00:00 EDT 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.81.053630· OSTI ID:21408887

Adhikari, S K ^[1]; Malomed, B A ^[2]; Salasnich, L; Toigo, F ^[3]

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1. Instituto de Fisica Teorica, Universidade Estadual Paulista, 01.140-070 Sao Paulo, Sao Paulo (Brazil)
2. Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)
3. Consiglio Nazionale delle Ricerche and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Unita di Padova, Dipartimento di Fisica 'Galileo Galilei', Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy)

We study the spontaneous symmetry breaking (SSB) of a superfluid Bose-Fermi (BF) mixture in a double-well potential (DWP). The mixture is described by the Gross-Pitaevskii equation (GPE) for the bosons, coupled to an equation for the order parameter of the Fermi superfluid, which is derived from the respective density functional in the unitarity limit (a similar model applies to the BCS regime, too). Straightforward SSB in the degenerate Fermi gas loaded into a DWP is impossible, as it requires an attractive self-interaction, and the intrinsic nonlinearity in the Fermi gas is repulsive. Nonetheless, we demonstrate that the symmetry breaking is possible in the mixture with attraction between fermions and bosons, like {sup 40}K and {sup 87}Rb. Numerical results are represented by dependencies of asymmetry parameters for both components on particle numbers of the mixture, N{sub F} and N{sub B}, and by phase diagrams in the (N{sub F},N{sub B}) plane, which displays regions of symmetric and asymmetric ground states. The dynamical picture of the SSB, induced by a gradual transformation of the single-well potential into the DWP, is reported too. An analytical approximation is proposed for the case when the GPE for the boson wave function may be treated by means of the Thomas-Fermi (TF) approximation. Under a special linear relationship between N{sub F} and N{sub B}, the TF approximation allows us to reduce the model to a single equation for the fermionic function, which includes competing repulsive and attractive nonlinear terms. The latter one directly displays the mechanism of the generation of the effective attraction in the Fermi superfluid, mediated by the bosonic component of the mixture.

• OSTI ID: 21408887
• Journal Information: Physical Review. A, Vol. 81, Issue 5; Other Information: DOI: 10.1103/PhysRevA.81.053630; (c) 2010 The American Physical Society; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
APPROXIMATIONS
BOSONS
DENSITY FUNCTIONAL METHOD
EQUATIONS
FERMI GAS
FERMIONS
GROUND STATES
MIXTURES
NONLINEAR PROBLEMS
ORDER PARAMETERS
PHASE DIAGRAMS
POTASSIUM 40
POTENTIALS
RUBIDIUM 87
SUPERFLUIDITY
SYMMETRY
SYMMETRY BREAKING
THOMAS-FERMI MODEL
WAVE FUNCTIONS
ATOMIC MODELS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CALCULATION METHODS
DIAGRAMS
DIMENSIONLESS NUMBERS
DISPERSIONS
ELECTRON CAPTURE RADIOISOTOPES
ENERGY LEVELS
FUNCTIONS
INFORMATION
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL MODELS
NANOSECONDS LIVING RADIOISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
POTASSIUM ISOTOPES
RADIOISOTOPES
RUBIDIUM ISOTOPES
VARIATIONAL METHODS
YEARS LIVING RADIOISOTOPES