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Evolution from BCS to Berezinskii-Kosterlitz-Thouless superfluidity in one-dimensional optical lattices
1Joint Quantum Institute, NIST and University of Maryland, Gaithersburg, Maryland 20899-8423, USA.
Physical Review Letters
|November 13, 2009
Summary
We studied fermion mixtures in optical lattices, finding a transition from 3D Bardeen-Cooper-Schrieffer superfluid to 2D Berezinskii-Kosterlitz-Thouless superfluid with increasing interactions. Vortex excitations change from loops to pairs.
Area of Science:
- Quantum physics
- Condensed matter physics
- Ultracold atomic gases
Background:
- Fermion mixtures in optical lattices exhibit complex phase diagrams.
- Understanding superfluidity in low dimensions is crucial for quantum many-body physics.
Purpose of the Study:
- To analyze the finite temperature phase diagram of 1D optical lattice fermion mixtures.
- To investigate the dimensional crossover from 3D Bardeen-Cooper-Schrieffer (BCS) to 2D Berezinskii-Kosterlitz-Thouless (BKT) superfluidity.
- To characterize the evolution of vortex excitations across this crossover.
Main Methods:
- Finite temperature phase diagram analysis.
- Calculation of critical temperature as a function of interaction strength.
- Identification of the dimensional crossover region for specific optical lattice potentials.
Main Results:
- The system transitions from an anisotropic 3D BCS superfluid to an effectively 2D BKT superfluid with increasing interaction strength at low temperatures.
- The critical temperature is calculated, and the region of dimensional crossover is identified.
- Dominant vortex excitations evolve from multiplane elliptical loops (3D) to planar vortex-antivortex pairs (2D) near the critical temperature.
Conclusions:
- The interaction strength dictates the dimensional crossover in fermion mixtures within optical lattices.
- Vortex excitation dynamics provide insights into the dimensionality of the superfluid state.
- A detection scheme for these vortex excitations is proposed.
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