Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
Q: Fachverband Quantenoptik und Photonik
Q 17: Fermi Quantum Gas
Q 17.4: Vortrag
Dienstag, 15. März 2011, 11:15–11:30, BAR Schön
Impurities in a 2D Fermi Gas — •Sascha Zöllner1, Georg M. Bruun2, and Christopher J. Pethick1 — 1Niels Bohr Institute, Copenhagen, Denmark — 2Aarhus University, Aarhus, Denmark
We study an impurity atom in a two-dimensional (2D) Fermi gas using variational wave functions for (i) an impurity dressed by particle-hole excitations (a so-called polaron) and (ii) a dimer consisting of the impurity and a majority atom. In contrast to 3D, where similar calculations predict a sharp transition to a dimer state with increasing interspecies attraction, the 2D polaron ansatz always gives a lower energy. However, the exact solution for a heavy impurity reveals that both a two-body bound state and distortions of the Fermi sea are crucial. This reflects the importance of particle-hole pairs in lower dimensions and makes simple variational calculations unreliable. Moreover, we show that the energy of an impurity gives important information about its dressing cloud, and what can be learned about the more general case of many (fermionic or bosonic) impurities.