# Berlin 2008 – wissenschaftliches Programm

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# TT: Fachverband Tiefe Temperaturen

## TT 38: Matter At Low Temperature: Quantum Liquids, Bose-Einstein Condensates, Ultra-cold Atoms, ...

### TT 38.3: Vortrag

### Freitag, 29. Februar 2008, 10:45–11:00, H 3010

**FFLO states in a one-dimensional lattice with polarized, trapped fermions and attractive interactions** — •Fabian Heidrich-Meisner^{1} and Adrian Feiguin^{2} — ^{1}Institut für Theoretische Physik C, RWTH Aachen, 52064 Aachen, Germany — ^{2}Microsoft Station Q, University of California, Santa Barbara, CA 93106, USA

We study the properties of a one-dimensional (1D) gas of fermions focusing on the case of unequal spin populations and strong attractive interaction. While the emergence of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states has previously been predicted from mean-field and local density approximation studies, here [1], we address this problem by means of a quasi-exact numerical method, the density matrix renormalization group technique. In the low density regime, the system phase-separates into a well defined superconducting core and a fully polarized metallic cloud surrounding it. We argue that the superconducting phase corresponds to a 1D analogue of the FFLO state, with a finite center-of-mass momentum that scales linearly with the magnetization. Moreover, we find that the spatial decay of pair correlations follows a power law. In the large density limit, the system allows for four phases: in the core, we either find a Fock state of localized pairs or a metallic shell with spin-down fermions moving in a fully filled background of spin-up fermions. As the magnetization increases, the Fock state disappears to give room for a metallic phase, with a partially polarized superconducting FFLO shell and a fully polarized metallic cloud surrounding the core.

[1] A.E. Feiguin, F. Heidrich-Meisner, arXiv:0707.4172.