Dynamical instability of a spin spiral in an interacting Fermi gas as a probe of the Stoner transition
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 76100 (Israel)
We propose an experiment to probe ferromagnetic phenomena in an ultracold Fermi gas, while alleviating the sensitivity to three-body loss and competing many-body instabilities. The system is initialized in a small pitch spin spiral, which becomes unstable in the presence of repulsive interactions. To linear order the exponentially growing collective modes exhibit critical slowing down close to the Stoner transition point. Also, to this order, the dynamics are identical on the paramagnetic and ferromagnetic sides of the transition. However, we show that scattering off the exponentially growing modes qualitatively alters the collective mode structure. The critical slowing down is eliminated and in its place a new unstable branch develops at large wave vectors. Furthermore, long-wavelength instabilities are quenched on the paramagnetic side of the transition. We study the experimental observation of the instabilities, specifically addressing the trapping geometry and how phase-contrast imaging will reveal the emerging domain structure. These probes of the dynamical phenomena could allow experiments to detect the transition point and distinguish between the paramagnetic and ferromagnetic regimes.
- OSTI ID:
- 21456982
- Journal Information:
- Physical Review. A, Vol. 82, Issue 4; Other Information: DOI: 10.1103/PhysRevA.82.043603; (c) 2010 The American Physical Society; ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
DOMAIN STRUCTURE
FERMI GAS
FERROMAGNETISM
INSTABILITY
PARAMAGNETISM
PHASE TRANSFORMATIONS
PROBES
SCATTERING
SENSITIVITY
SLOWING-DOWN
SPIN
THREE-BODY PROBLEM
TRAPPING
VECTORS
ANGULAR MOMENTUM
MAGNETISM
MANY-BODY PROBLEM
PARTICLE PROPERTIES
TENSORS