外电场驱动下Holstein极化子的非平衡动力学
Nonequilibrium dynamics of the Holstein polaron driven by external electric field
摘要：
这一工作代表了对一维Holstein极化子在恒定电场作用下被驱离基态的基本研究。充分考虑到量子效应，我们遵循系统从其基态的时间演化，因为恒定电场在t = 0时被打开，直到它达到稳定状态。在弱的电子-声子耦合（EP）下，系统经历非相互作用电子带的阻尼布洛赫振荡（BO）特征。在弱EP耦合和大电场条件下，给出了稳态电流的解析表达式。对于EP耦合的中等值，振荡几乎是临界阻尼的，并且系统在短时间后达到稳态。在强耦合限制弱阻尼BO，符合近绝热演化的极化子带内，坚持到非常大的电场。在电场影响下的移动极化子留下声子激发的踪迹，吸收从电场获得的多余能量。详细研究了极化子的形状。
英文摘要：
This work represents a fundamental study of a Holstein polaron in one dimension driven away from the ground state by a constant electric field. Taking fully into account quantum effects we follow the time-evolution of the system from its ground state as the constant electric field is switched on at t = 0, until it reaches a steady state. At weak electron phonon coupling (EP) the system experiences damped Bloch oscillations (BO) characteristic for noninteracting electron band. An analytic expression of the steady state current is proposed in terms of weak EP coupling and large electric field. For moderate values of EP coupling the oscillations are almost critically damped and the system reaches the steady state after a short time. In the strong coupling limit weakly damped BO, consistent with nearly adiabatic evolution within the polaron band, persist up to extremely large electric fields. A traveling polaron under the influence of the electric field leaves behind a trail of phonon excitations absorbing the excess energy gained from the electric field. The shape of the traveling polaron is investigated in details.
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