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arXiv 1005.4476cond-mat.str-el
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合成周期磁场中的超冷玻色子:莫特相和再入超流-绝缘体跃迁

Ultracold bosons in a synthetic periodic magnetic field: Mott phases and re-entrant superfluid-insulator transitions

K. Saha, K. Sengupta, K. Ray

摘要:

研究了二维正方形光晶格中超冷玻色子原子在公度填充和存在周期矢量势的情况下的Mott相和超流-绝缘体(SI)跃迁,矢量势的特征为强度$p$和周期$l=qa$,其中$q$为整数,$a$为晶格间距.我们表明,薛定谔方程的非相互作用玻色子在这种周期性的矢量势的存在下,可以减少到一个一维的Harper类方程,产生$q$能带。这些频带中的最低频带具有单极小值或双极小值,其在磁布里渊区内的位置可以通过针对给定的$q$改变$p$来调谐。利用这些能量和强耦合展开技术,我们计算了这些玻色子在深光晶格中的相图。我们绘制了玻色子在SI跃迁附近的Mott相动量分布的$p$和$q$依赖关系图,并证明了对于任何固定周期的$q$,玻色子都表现出多次再入场诱导的SI跃迁.我们还预测,超流密度产生的超流态附近的SI转变具有周期性$q$($q/2$)在实空间的奇(偶)$q$,并建议实验来验证我们的理论。

英文摘要:

We study Mott phases and superfluid-insulator (SI) transitions of ultracold bosonic atoms in a two-dimensional square optical lattice at commensurate filling and in the presence of a synthetic periodic vector potential characterized by a strength $p$ and a period $l=qa$, where $q$ is an integer and $a$ is the lattice spacing. We show that the Schrödinger equation for the non-interacting bosons in the presence of such a periodic vector potential can be reduced to an one-dimensional Harper-like equation which yields $q$ energy bands. The lowest of these bands have either single or double minima whose position within the magnetic Brillouin zone can be tuned by varying $p$ for a given $q$. Using these energies and a strong-coupling expansion technique, we compute the phase diagram of these bosons in the presence of a deep optical lattice. We chart out the $p$ and $q$ dependence of the momentum distribution of the bosons in the Mott phases near the SI transitions and demonstrate that the bosons exhibit several re-entrant field-induced SI transitions for any fixed period $q$. We also predict that the superfluid density of the resultant superfluid state near such a SI transition has a periodicity $q$ ($q/2$) in real space for odd (even) $q$ and suggest experiments to test our theory.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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