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arXiv 0811.1224cond-mat.str-elcond-mat.supr-con
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具有环交换作用的格点玻色子的超流和超固相

Superfluid and supersolid phases of lattice bosons with ring-exchange interaction

Robert Schaffer, Anton A. Burkov, Roger G. Melko

摘要:

本文研究了正方形晶格上具有最近邻交换J和四粒子环交换K的硬核玻色子模型的超流相。在零温度下,我们发现,在纯J模型的超流很快被破坏的包含负K环交换相互作用,有利于一个状态(π,π)有序波矢量。平均场能量的最小化表明形成了一种超固态,同时存在超流性、电荷密度波和类价键有序。通过对有限T自旋波超流密度施加Nelson-Kosterlitz普适跳跃条件,我们还研究了超流相中有限T自旋波Kosterlitz无相变相变的行为.远离纯J点,T_{KT}在负K时迅速减小,而在正K时,T_{KT}在某个K \neq 0处达到最大值,这与最近的量子蒙特卡罗模拟一致。

英文摘要:

We examine the superfluid phase of a hard-core boson model with nearest-neighbor exchange J and four-particle ring-exchange K at half-filling on the square lattice. At zero temperature we find that the superfluid in the pure-J model is quickly destroyed by the inclusion of negative-K ring-exchange interactions, favoring a state with a (pi,pi) ordering wavevector. Minimization of the mean-field energy suggests that a supersolid state with coexisting superfluidity, charge-density wave, and valence-bond-like order is formed. We also study the behavior of the finite-T Kosterlitz-Thouless phase transition in the superfluid phase, by forcing the Nelson-Kosterlitz universal jump condition on the finite-T spin wave superfluid density. Away from the pure J point, T_{KT} decreases rapidly for negative K, while for positive K, T_{KT} reaches a maximum at some K \neq 0 in agreement with recent quantum Monte Carlo simulations.

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