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arXiv 1111.6182cond-mat.stat-mech
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谐波结热输运的计数统计--瞬态和稳态

Counting statistics of heat transport in harmonic junctions -- transient and steady states

Bijay Kumar Agarwalla, Baowen Li, Jian-Sheng Wang

摘要:

我们研究了在给定的时间间隔$t_M$,通过一个有限的谐波链,称为中心$(C)$,这是连接到两个热浴,左$(L)$和右$(R)$,这是保持在两个不同的温度下的热传递的统计。中心原子受到外部时间依赖力的驱动。基于两次测量的概念,采用非平衡格林函数(NEGF)方法,计算了左电极导线($Q_L$)输出热量的累积母函数(CGF)。CGF可以简明地表示为中心的格林函数和一个自变量移动的铅的自能。CGF的表达式是有效的瞬态和稳态制度。我们考虑三种不同的初始条件的密度算子和数值显示,一维(1D)的线性链,如何瞬态行为彼此不同,但最终接近相同的稳定状态,独立的初始分布。我们还推导了联合概率分布$P(Q_L,Q_R)$的CGF,并讨论了$Q_L$和$Q_R$之间的相关性。我们计算了进入水库的总熵流。在稳态下,我们明确表明,CGF服从稳态涨落定理(SSFT)。采用$\hbar \to 0$得到经典结果。该方法也适用于电子数和电子能量的计数,其中相关的自能是由通常的铅自能通过乘以相位或移动轮廓时间,分别获得。

英文摘要:

We study the statistics of heat transferred in a given time interval $t_M$, through a finite harmonic chain, called the center $(C)$, which is connected with two heat baths, the left $(L)$ and the right $(R)$, that are maintained at two different temperatures. The center atoms are driven by an external time-dependent force. We calculate the cumulant generating function (CGF) for the heat transferred out of the left lead, $Q_L$, based on two-time measurement concept and using nonequilibrium Green's function (NEGF) method. The CGF can be concisely expressed in terms of Green's functions of the center and an argument-shifted self-energy of the lead. The expression of CGF is valid in both transient and steady state regimes. We consider three different initial conditions for the density operator and show numerically, for one-dimensional (1D) linear chains, how transient behavior differs from each other but finally approaches the same steady state, independent of the initial distributions. We also derive the CGF for the joint probability distribution $P(Q_L,Q_R)$, and discuss the correlations between $Q_L$ and $Q_R$. We calculate the total entropy flow to the reservoirs. In the steady state we explicitly show that the CGF obeys steady state fluctuation theorem (SSFT). Classical results are obtained by taking $\hbar \to 0$. The method is also applied to the counting of the electron number and electron energy, for which the associated self-energy is obtained from the usual lead self-energy by multiplying a phase or shifting the contour time, respectively.

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