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Rotons in interacting ultracold bose gases
Samuel C Cormack1, Dániel Schumayer, David A W Hutchinson
1Jack Dodd Centre for Quantum Technology, Department of Physics, University of Otago, Dunedin, New Zealand.
Physical Review Letters
|November 24, 2011
Summary
Interacting bosons exhibit a roton minimum in their excitation spectrum, linked to a critical temperature shift. This study explains the roton emergence and suggests experimental observations in Bose-Einstein condensates.
Area of Science:
- Quantum mechanics
- Condensed matter physics
- Bose-Einstein condensation
Background:
- Noninteracting bosons condense at a critical temperature T(c).
- Interactions shift this critical temperature by ΔT(c).
- Understanding these shifts requires analyzing the excitation spectrum.
Purpose of the Study:
- To calculate the excitation spectrum of interacting Bose systems.
- To investigate the emergence of a roton minimum.
- To theoretically link the roton minimum to the critical temperature shift.
Main Methods:
- Path-integral Monte Carlo simulations.
- Analysis of excitation spectra for (4)He and (87)Rb.
- Theoretical modeling of short-range two-body interactions.
Main Results:
- A roton minimum emerges in the excitation spectrum above a threshold gas parameter.
- The roton minimum is theoretically linked to the maximal upward critical temperature shift.
- Microscopic explanation for the critical temperature shift is provided.
Conclusions:
- Interacting Bose systems can develop a roton minimum.
- This roton minimum is a key feature explaining the shift in critical temperature.
- Experimental methods for observing rotons in condensates are proposed.
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