Heidelberg 2015 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
Q: Fachverband Quantenoptik und Photonik
Q 4: Quantum Gases: Fermions I
Q 4.1: Vortrag
Montag, 23. März 2015, 11:30–11:45, K/HS2
Observation of Leggett-Rice effect in a unitary Fermi gas — •Tilman Enss1, Stefan Trotzky2, Scott Beattie2, Chris Luciuk2, Scott Smale2, Alma Bardon2, Edward Taylor3, Shizhong Zhang4, and Joseph Thywissen2 — 1Universität Heidelberg — 2University of Toronto, Canada — 3McMaster University, Canada — 4University of Hong Kong, China
We observe that the diffusive spin current in a strongly interacting degenerate Fermi gas of 40K precesses about the local magnetization. As predicted by Leggett and Rice, precession is observed both in the Ramsey phase of a spin-echo sequence, and in the nonlinearity of the magnetization decay. At unitarity, we measure a Leggett-Rice parameter γ = 1.08(9) and a bare transverse spin diffusivity D0⊥= 2.3(4) ℏ/m for a normal-state gas initialized with full polarization at T/TF=0.2. Tuning the scattering length a, we find that a sign change in γ occurs near unitarity. We argue how γ reveals the effective interaction strength of the gas, such that the sign change in γ indicates a switching of branch, between a repulsive and an attractive Fermi gas.