Radio-frequency spectroscopy of ultracold fermions.
Radio-frequency techniques were used to study ultracold fermions. We observed the absence of mean-field "clock" shifts, the dominant source of systematic error in current atomic clocks based on bosonic atoms. This absence is a direct consequence of fermionic antisymmetry. Resonance shifts proportional to interaction strengths were observed in a three-level system. However, in the strongly interacting regime, these shifts became very small, reflecting the quantum unitarity limit and many-body effects. This insight into an interacting Fermi gas is relevant for the quest to observe superfluidity in this system.
Department of Physics, Massachusetts Institute of Technology (MIT)-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, MIT, Cambridge, MA 02139, USA. deep@mit.edu
S
S
Gupta
Z
Z
Hadzibabic
M W
MW
Zwierlein
C A
CA
Stan
K
K
Dieckmann
C H
CH
Schunck
E G M
EG
Van Kempen
B J
BJ
Verhaar
W
W
Ketterle