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arXiv 1908.04666cond-mat.mes-hallphysics.app-ph
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扭曲双层石墨烯的热力学模型:构型熵的作用

Thermodynamic model of twisted bilayer graphene: Configuration entropy matters

Weidong Yan, Langquan Shui, Wengen Ouyang, Ze Liu

摘要:

扭曲双层材料由于其独特的性质而引起了人们的极大关注。在经典统计力学的框架下,推导了扭曲双层石墨烯(tBLG)的热力学模型,并在此基础上,从亥姆霍兹自由能直接推导出反映莫尔晶胞微观状态个数的组态熵,给出了清晰的物理解释.更重要的是,我们发现tBLG相对于AB堆叠的双层石墨烯的配置熵与莫尔周期和原子晶格常数的比率的对数函数成比例,我们发现这支配了tBLG的亥姆霍兹自由能,并且可以很好地解释超润滑接触中的实验观察。本文的工作为研究非公度接触界面的莫尔效应提供了理论基础,并可用于超润滑等基于扭转的应用。

英文摘要:

Twisted bilayer materials have attracted tremendous attention due to their unique and novel properties. Here, we derive a thermodynamic model for twisted bilayer graphene (tBLG) within the framework of the classical statistical mechanics, based on which, the configuration entropy reflecting the number of micro-status in moire unit-cells, is directly derived from the Helmholtz free energy with a clear physical interpretation. More importantly, we show the configuration entropy of tBLG relative to the AB-stacked bilayer graphene is proportional to the logarithmic function of the ratio of moire period and the atomic lattice constant, which we found dominates the Helmholtz free energy of tBLG and can well explain experimental observations in superlubric contacts. Our work provides a theoretical foundation for studying moire effect of incommensurate contact interfaces and could facilitate twisting based applications such as superlubricity.

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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