August 30, 2010 to September 24, 2010
Europe/Stockholm timezone

Excitation spectrum of a 2D long-range Bose liquid with a supersymmetry

Sep 20, 2010, 1:30 PM
132:028 (Nordita)




Jenia MOZGUNOV (Landau Institute for Theoretical Physics)


Specic model of a 2D Bose liquid with non-relativistic supersymmetry [1, 2] is studied numerically by means of a mapping to a classical Langevin dynamics [3, 4]. The model contains dimensionless coupling constant . At small 1 this model is very similar to the 2D Bose-lqiuid with pair-wise logarithmic interaction and thus exibit superuid ground state. At very large 35 the ground state nearly breaks translational symmetry: equal-time density correlations in the emergent ground state are equivalent to those of the classical 2D crystal at nonzero temperature. We have studied the excitation spectrum of this model in the whole range of by means of the analysis of the dynamic structure factor S(k, t) computed for the equivalent classical model, like it was done in Ref. [5] for the model of quantum dimers at the Rokshar-Kivelson point [6]. The spectrum !(q) we found contains a plasmon gap !0 at q = 0 and a well-dened roton minimum at q = q0 = 2 p n with minimal excitation energy . The ratio /!0 decreases sharply with in the whole range of the strongly coupled Bose liquid 1 < < 35, down to very small values 10−2. However, we could not detect, with our numerical accurace, a vanishing of the roton gap before 2D crystallization transition takes place at = c 37.We thus conclude that the ground-state is of superuid nature (at T = 0) in the whole range of < c (however, the critical temperature Tc of superuid transition drops sharply with ). In the crystalline state > c no well-dened low- energy excitations corresponding to shear modes was found, in agreement with theoretically expected spectrum !(k) / k2 that suggests strongly decaying nature of the corresponding quasiparticles.
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[4] C.L. Henley, J. Phys.: Condens. Matter 16, S891 (2004).
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