Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 5: Spin Structures and Magnetic Phase Transitions
MA 5.8: Vortrag
Montag, 26. März 2012, 11:30–11:45, H 0112
Phase diagram of hard-core bosons on clean and disordered 2-leg ladders: Mott insulator, Luttinger liquid, Bose glass — •Francois Crepin1, Nicolas Laflorencie2, Pascal Simon3, and Guillaume Roux4 — 1Institute for Theoretical Physics and Astrophysics, University of Würzburg, 97074 Würzburg, Germany — 2LPT, Université de Toulouse, UPS (IRSAMC), Toulouse, France — 3LPS, Université Paris-Sud, UMR-8502 CNRS, F-91405 Orsay, France — 4LPTMS, Université Paris-Sud, UMR-8626 CNRS, F-91405 Orsay, France
While one-dimensional free fermions and hard-core bosons are often considered to be equivalent, coupling only two chains enables particle exchange and leads to totally different physics for free fermions and HC bosons. Combining analytical (strong coupling, field theory) and numerical (quantum Monte Carlo, DMRG) approaches, we study the apparently simple but nontrivial model of HC bosons in a two-leg ladder geometry. At half-filling, while a band insulator appears for fermions at large interchain hopping t⊥> 2t only, a Mott gap opens up for bosons as soon as t⊥≠ 0 through a Kosterlitz-Thouless transition. Away from half-filling, a gapless Luttinger liquid mode emerges in the symmetric sector with a nontrivial filling-dependent Luttinger parameter 1/2 ≤ Ks ≤ 1. We discuss consequences for experiments on spin ladders in a magnetic field and cold atoms, as well as disorder effects. Indeed, a quantum phase transition at finite disorder strength is expected, between a 1D superfluid and an insulating Bose glass phase. F. Crépin et al., Phys. Rev. B, 84, 054517 (2011)