Séminaire du LPTMS: Marie Piraud (ATTENTION horaire inhabituel)


11:30 - 12:30

LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay
15 Rue Georges Clemenceau, Orsay, 91405

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Interacting bosons on ladder in the presence of gauge fields: Swimming against the tide !

Marie Piraud, Ludwig-Maximilians-Universität München

We present the phase diagrams of the interacting Bose-Hubbard model defined on two- and three-leg ladder geometries in the presence of a homogeneous flux. Our work is motivated by recent experiments using laser assisted-tunneling in optical lattices [1] and lattices in synthetic dimensions [2], which studied the regime of weak interactions. Based on extensive density matrix renormalization group simulations and a bosonization analysis for the two-leg ladder, we explore the parameter space and calculate experimentally accessible observables.
The phase diagrams comprise gapless and gapped Meissner and vortex phases, with the gapped states emerging in Mott-insulating regimes [3,4]. We show that vortex lattices also form at certain commensurate vortex densities [4,5]. On the two-leg ladder, we also find the so-called ‘biased leg phase’, which shows density-imbalance between the two legs [6].
Very interestingly, an enlarged unit cell forms in the vortex lattice phases, which can lead to the reversal of the current circulation-direction. We demonstrate this effect for arbitrarily weak interactions and at sufficiently low temperature, and show that it is significant for intermediate interactions [5].
[1] Atala etal., Nature Phys. 10, 588 (2014)
[2] Mancini etal., Science 349, 1510-1513 (2015)
[3] Piraud etal., PRB 91, 140406(R) (2015)
[4] Kolley etal., NJP 17, 092001 (2015)
[5] Greschner etal., to appear in PRL (2015)
[6] Wei and Mueller, PRA 89, 063617 (2014)
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