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arXiv · 1309.2769

Supersolid structure and excitation spectrum of soft-core bosons in 3D

Francesco Ancilotto·Maurizio Rossi·Flavio Toigo
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Abstract

By means of a mean-field method, we have studied the zero temperature structure and excitation spectrum of a three-dimensional soft-core bosonic system for a value of the interaction strength that favors a crystal structure made of atomic nano-clusters arranged with FCC ordering. In addition to the longitudinal and transverse phonon branches expected for a normal crystal, the excitation spectrum shows a soft mode related to the breaking of gauge symmetry, which signals a partial superfluid character of the solid. Additional evidence of supersolidity is provided by the calculation of the superfluid fraction, which shows a first-order drop, from 1 to 0.4, at the liquid-supersolid transition and a monotonic decrease as the interaction strength parameter is increased. The conditions for the coexistence of the supersolid with the homogeneous superfluid are discussed, and the surface tension of a representative solid-liquid interface is calculated.

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Francesco Ancilotto, Maurizio Rossi, Flavio Toigo. 2013-09-11. Supersolid structure and excitation spectrum of soft-core bosons in 3D. https://doi.org/10.1103/physreva.88.033618

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