Density and spin response functions in ultracold fermionic atom gases

We propose a new method of detecting the onset of superfluidity in a two-component ultracold fermionic gas of atoms governed by an attractive short-range interaction. By studying the two-body correlation functions we find that a measurement of the momentum distribution of the density and spin-respon...

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Bibliographic Details
Published in:Physical review letters 2005-08, Vol.95 (9), p.090402.1-090402.4, Article 090402
Main Authors: MIHAILA, Bogdan, GAUDIO, Sergio, BLAGOEV, Krastan B, BALATSKY, Alexander V, LITTLEWOOD, Peter B, SMITH, Darryl L
Format: Article
Language:English
Subjects:
ATOMS
BCS THEORY
BOSE-EINSTEIN CONDENSATION
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
CORRELATION FUNCTIONS
Exact sciences and technology
FERMIONS
GASES
INTERACTION RANGE
MAGNETIC FIELDS
MOMENTUM TRANSFER
Physics
RESPONSE FUNCTIONS
SPIN
SUPERFLUIDITY
SYMMETRY BREAKING
TWO-BODY PROBLEM
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Summary:We propose a new method of detecting the onset of superfluidity in a two-component ultracold fermionic gas of atoms governed by an attractive short-range interaction. By studying the two-body correlation functions we find that a measurement of the momentum distribution of the density and spin-response functions allows one to access separately the normal and anomalous densities. The change in sign at low momentum transfer of the normal-ordered part of the density response function signals the transition between a BEC and a BCS regime, characterized by small and large pairs, respectively. This change in sign of the density response function represents an unambiguous signature of the BEC-to-BCS crossover. Spin rotational symmetry breaking due to the magnetic field, if observed, can be used to validate the one-channel model.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.95.090402