# Momentum Distribution and Condensate Fraction of a Fermion Gas in the BCS-BEC Crossover

## Abstract

By using the diffusion Monte Carlo method we calculate the one- and two-body density matrix of an interacting Fermi gas at T=0 in the BCS to Bose-Einstein condensate (BEC) crossover. Results for the momentum distribution of the atoms, as obtained from the Fourier transform of the one-body density matrix, are reported as a function of the interaction strength. Off-diagonal long-range order in the system is investigated through the asymptotic behavior of the two-body density matrix. The condensate fraction of pairs is calculated in the unitary limit and on both sides of the BCS-BEC crossover.

- Authors:

- Dipartimento di Fisica and BEC-INFM, Universita di Trento, I-38050 Povo (Italy)
- (Russian Federation)
- Departament de Fisica i Enginyeria Nuclear, Campus Nord B4-B5, Universitat Politecnica de Catalunya, E-08034 Barcelona (Spain)
- JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States)
- (Italy)

- Publication Date:

- OSTI Identifier:
- 20699632

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Physical Review Letters; Journal Volume: 95; Journal Issue: 23; Other Information: DOI: 10.1103/PhysRevLett.95.230405; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMS; BCS THEORY; BOSE-EINSTEIN CONDENSATION; DENSITY MATRIX; FERMI GAS; FERMIONS; FOURIER TRANSFORMATION; MONTE CARLO METHOD; TWO-BODY PROBLEM

### Citation Formats

```
Astrakharchik, G.E., Institute of Spectroscopy, 142190 Troitsk, Boronat, J., Casulleras, J., Giorgini, S., and Dipartimento di Fisica and BEC-INFM, Universita di Trento, I-38050 Povo.
```*Momentum Distribution and Condensate Fraction of a Fermion Gas in the BCS-BEC Crossover*. United States: N. p., 2005.
Web. doi:10.1103/PhysRevLett.95.230405.

```
Astrakharchik, G.E., Institute of Spectroscopy, 142190 Troitsk, Boronat, J., Casulleras, J., Giorgini, S., & Dipartimento di Fisica and BEC-INFM, Universita di Trento, I-38050 Povo.
```*Momentum Distribution and Condensate Fraction of a Fermion Gas in the BCS-BEC Crossover*. United States. doi:10.1103/PhysRevLett.95.230405.

```
Astrakharchik, G.E., Institute of Spectroscopy, 142190 Troitsk, Boronat, J., Casulleras, J., Giorgini, S., and Dipartimento di Fisica and BEC-INFM, Universita di Trento, I-38050 Povo. Fri .
"Momentum Distribution and Condensate Fraction of a Fermion Gas in the BCS-BEC Crossover". United States.
doi:10.1103/PhysRevLett.95.230405.
```

```
@article{osti_20699632,
```

title = {Momentum Distribution and Condensate Fraction of a Fermion Gas in the BCS-BEC Crossover},

author = {Astrakharchik, G.E. and Institute of Spectroscopy, 142190 Troitsk and Boronat, J. and Casulleras, J. and Giorgini, S. and Dipartimento di Fisica and BEC-INFM, Universita di Trento, I-38050 Povo},

abstractNote = {By using the diffusion Monte Carlo method we calculate the one- and two-body density matrix of an interacting Fermi gas at T=0 in the BCS to Bose-Einstein condensate (BEC) crossover. Results for the momentum distribution of the atoms, as obtained from the Fourier transform of the one-body density matrix, are reported as a function of the interaction strength. Off-diagonal long-range order in the system is investigated through the asymptotic behavior of the two-body density matrix. The condensate fraction of pairs is calculated in the unitary limit and on both sides of the BCS-BEC crossover.},

doi = {10.1103/PhysRevLett.95.230405},

journal = {Physical Review Letters},

number = 23,

volume = 95,

place = {United States},

year = {Fri Dec 02 00:00:00 EST 2005},

month = {Fri Dec 02 00:00:00 EST 2005}

}

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