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arXiv 2101.03062cond-mat.mes-hallquant-ph
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三层石墨烯中的门控正反向电热效应

Gate-tunable direct and inverse electrocaloric effect in trilayer graphene

Natalia Cortés, Oscar Negrete, Francisco J. Peña, Patricio Vargas

摘要:

电热(EC)效应是当材料经受绝热电场变化时材料的温度和/或熵的可逆变化。我们的紧束缚计算与费米统计相关联,表明EC效应对连接到热源的三层石墨烯(TLG)结构中的堆叠排列敏感,并且当外部栅极场施加在外部石墨烯层上时,通过费米能级附近的电子态密度(DOS)的变化产生。我们证明了AAA堆叠TLG提出了一个逆EC响应(冷却),而在ABC堆叠TLG的EC效果仍然是直接的(加热),无论施加的栅极场电位强度。我们揭示,否则的TLG与Bernal-ABA堆叠几何产生的逆和直接EC响应在同一个样品中,在有限的温度下与门相关的电子熵跃迁。通过改变化学势到不同的费米能级,我们发现DOS的最大值和最小值都位于电子熵的极值附近,这与每个粒子的微分熵的符号变化相关,给出了每个TLG几何形状的特定实验可测量的电子熵谱。量子二维分层系统中的EC效应可能会带来各种各样的原型范德华材料,这些材料可以用作控制现代便携式芯片技术所需的纳米级电子器件中的温度的通用平台。

英文摘要:

The electrocaloric (EC) effect is the reversible change in temperature and/or entropy of a material when it is subjected to an adiabatic electric field change. Our tight-binding calculations linked to Fermi statistics, show that the EC effect is sensitive to the stacking arrangement in trilayer graphene (TLG) structures connected to a heat source, and is produced by changes of the electronic density of states (DOS) near the Fermi level when external gate fields are applied on the outer graphene layers. We demonstrate the AAA-stacked TLG presents an inverse EC response (cooling), whereas the EC effect in ABC-stacked TLG remains direct (heating) regardless of the applied gate field potential strength. We reveal otherwise the TLG with Bernal-ABA stacking geometry generates both the inverse and direct EC response in the same sample, associated with a gate-dependent electronic entropy transition at finite temperature. By varying the chemical potential to different Fermi levels, we find maxima and minima of the DOS are located near the extremes of the electronic entropy, which are correlated with sign changes in the differential entropy per particle, giving a particular experimentally measurable electronic entropy spectrum for each TLG geometry. The EC effect in quantum two-dimensional layered systems may bring a wide variety of prototype van der Waals materials that could be used as versatile platforms to controlling the temperature in nanoscale electronic devices required in modern portable on-chip technologies.

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