laboratoire de physique statistique
 
 
laboratoire de physique statistique
 

Quantum many-body theory



Faculty
Xavier LEYRONAS
Kris VAN HOUCKE

Emeritus
Roland COMBESCOT

PhD Students
Riccardo ROSSI

Roland Combescot, Xavier Leyronas and Kris Van Houcke are interested in condensed matter problems in which interactions between fermions are important. The technics they use are the one of quantum field theory applied to the many-body problem.
In particular, they use Feynman diagrams (see Figures) in the physics of ultra cold atoms and semi-conductors.

Recently, they have worked on the following problems:
- the « BEC-BCS » crossover
- the polaron problem in ultra cold atoms
- the virial expansion
- the Hubbard model (with the help of Feynman diagrams sampled by a Monte Carlo simulation)
- few-body (3 or 4) problems as they occur in ultra cold atoms

Links to web pages:
RC : http://www.lps.ens.fr/~combesco/
XL : http://www.lps.ens.fr/~leyronas/
KVH : ?

Links to arxiv:
XL: http://arxiv.org:443/find/all/1/au:+Leyronas_X/0/1/0/all/0/1?per_page=100
RC: http://arxiv.org:443/find/all/1/au:+Combescot_R/0/1/0/all/0/1?per_page=100
KVH: http://arxiv.org:443/find/all/1/au:+Van_Houcke_K/0/1/0/all/0/1?per_page=100

FIGURES :

JPEG - 12.7 kb
Feynman diagrams used for the calculation of the third-orderf virial coefficient . This work was motivated by experiments performed in the group of C. salomon and F. Chevy of LKB
Principle of a self-consistent diagrammatic calculation. Millions of diagrams are sampled, up to order 8
PNG - 90.2 kb
Maps of spatial coherence of the light emitted when excitons spontaneously annihilate in a Bose-Einstein condensate of excitons (temperature is 0.34 K).