Bloch oscillations of bosonic lattice polarons
Bloch oscillations of bosonic lattice polarons
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DOI：
10.1103/physreva.90.063610
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发表时间：
2014-12-04
影响因子：
2.9
通讯作者：
Demler, E.
中科院分区：
文献类型：
--
作者：
Grusdt, F.;Shashi, A.;Demler, E.
我们考虑将单杂质原子限制在光学晶格中并浸入均匀的玻色-爱因斯坦凝聚体（BEC）中。杂质与 BEC 声子模式的相互作用导致形成稳定的准粒子，即极化子。我们使用变分平均场方法来研究色散重整化，并通过将运动方程投影到平均场型波函数来推导描述极化子非平衡动力学的方程。作为一个具体的例子，我们应用我们的方法来研究杂质原子响应突然施加的力的动力学，并探索相干布洛赫振荡和非相干漂移的相互作用。我们获得了漂移速度对所施加力的非线性依赖性，包括 BEC 维度 d > 1 的小力的亚欧姆依赖性。对于重杂质原子的情况，我们推导了漂移速度的封闭解析表达式。我们的结果显示与常用的现象学 Esaki-Tsu 模型有很大差异。
We consider a single-impurity atom confined to an optical lattice and immersed in a homogeneous Bose-Einstein condensate (BEC). Interaction of the impurity with the phonon modes of the BEC leads to the formation of a stable quasiparticle, the polaron. We use a variational mean-field approach to study dispersion renormalization and derive equations describing nonequilibrium dynamics of polarons by projecting equations of motion into mean-field-type wave functions. As a concrete example, we apply our method to study dynamics of impurity atoms in response to a suddenly applied force and explore the interplay of coherent Bloch oscillations and incoherent drift. We obtain a nonlinear dependence of the drift velocity on the applied force, including a sub-Ohmic dependence for small forces for dimensionality d > 1 of the BEC. For the case of heavy impurity atoms, we derive a closed analytical expression for the drift velocity. Our results show considerable differences with the commonly used phenomenological Esaki-Tsu model.