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Excitations of one-dimensional Bose-Einstein condensates in a random potential
V Gurarie1, G Refael, J T Chalker
1Department of Physics, University of Colorado, Boulder, CO 80309, USA.
Physical Review Letters
|November 13, 2008
Summary
We studied bosons on a lattice with random potential. The localization length exponent (alpha) changes with disorder strength, revealing a transition from superfluid to insulator behavior.
Area of Science:
- Condensed matter physics
- Quantum many-body systems
Background:
- Bose-Einstein condensates (BECs) in disordered potentials exhibit localized excitations.
- The localization length exponent (alpha) characterizes this localization, with a known value for weak disorder.
Purpose of the Study:
- To investigate how the localization length exponent (alpha) of Bogoliubov excitations in a 1D lattice BEC changes with increasing random potential strength.
- To identify the critical disorder strength at which the BEC transitions from a superfluid to an insulating state.
Main Methods:
- Theoretical analysis of bosons hopping on a 1D lattice with a random potential at zero temperature.
- Calculation of the localization length (l(omega)) of Bogoliubov excitations as a function of frequency (omega) and disorder strength.
Main Results:
- The exponent alpha=2, previously established for weak disorder, is only valid below a critical disorder strength.
- As disorder increases, alpha decreases, indicating a modification of excitation localization.
- At the superfluid-insulator transition, the exponent reaches alpha=1.
Conclusions:
- The exponent characterizing Bogoliubov excitation localization in disordered 1D BECs is not universally constant.
- A critical disorder strength exists, marking a transition from superfluidity to insulating behavior, with a distinct localization exponent.
- These findings are crucial for understanding disordered BECs and Josephson junction arrays.
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