利用布朗热马达在一维均匀非线性晶格中穿梭传热
Shuttling heat across 1D homogenous nonlinear lattices with a Brownian heat motor
摘要：
我们研究了平均无净热偏置时一维均匀非线性晶格中的定向热通量。Fermi-Pasta-Ulam型或Lennard-Jones型系统的非线性晶格在两端连接到在时间平均上保持在相同温度的热浴。我们研究了两种不同的调制的热浴温度，即：（i）一个对称的，谐波交流驱动的温度只有一个热浴和（ii）谐波混合驱动的温度作用于两个热浴。虽然对于情况（i），可以根据非线性晶格的温度相关热导率导出净热传输的绝热结果，但类似的这种传输方法对于谐波混合情况（ii）失败。然后，对于情况（ii），甚至所得到的布朗运动引起的热通量的符号也不能被先验地预测。一个非零的热通量（包括一个非绝热逆转的通量）被检测到，这是一个诱导的动态对称性破缺机制结合晶格动力学的非线性的结果。计算机模拟表明，热通量对晶格尺寸的增加是鲁棒的。所观察到的棘轮效应，这种定向热流是相当大的，我们研究类的同质非线性晶格结构，从而使这种设置可用于实验实施和验证。
英文摘要：
We investigate directed thermal heat flux across 1D homogenous nonlinear lattices when no net thermal bias is present on average. A nonlinear lattice of Fermi-Pasta-Ulam-type or Lennard-Jones-type system is connected at both ends to thermal baths which are held at the same temperature on temporal average. We study two different modulations of the heat bath temperatures, namely: (i) a symmetric, harmonic ac-driving of temperature of one heat bath only and (ii) a harmonic mixing drive of temperature acting on both heat baths. While for case (i) an adiabatic result for the net heat transport can be derived in terms of the temperature dependent heat conductivity of the nonlinear lattice a similar such transport approach fails for the harmonic mixing case (ii). Then, for case (ii), not even the sign of the resulting Brownian motion induced heat flux can be predicted a priori. A non-vanishing heat flux (including a non-adiabatic reversal of flux) is detected which is the result of an induced dynamical symmetry breaking mechanism in conjunction with the nonlinearity of the lattice dynamics. Computer simulations demonstrate that the heat flux is robust against an increase of lattice sizes. The observed ratchet effect for such directed heat currents is quite sizable for our studied class of homogenous nonlinear lattice structures, thereby making this setup accessible for experimental implementation and verification.
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