Jayaraman Aditya, Hsieh Kimberly, Ghawri Bhaskar, Mahapatra Phanibhusan S, Watanabe Kenji, Taniguchi Takashi, Ghosh Arindam
Department of Physics, Indian Institute of Science, Bangalore 560012, India.
Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
Nano Lett. 2021 Feb 10;21(3):1221-1227. doi: 10.1021/acs.nanolett.0c03586. Epub 2021 Jan 27.
Resolving low-energy features in the density of states (DOS) holds the key to understanding a wide variety of rich novel phenomena in graphene-based 2D heterostructures. The Lifshitz transition in bilayer graphene (BLG) arising from trigonal warping has been established theoretically and experimentally. Nevertheless, the experimental realization of its effects on transport properties has been challenging because of its relatively low energy scale (∼1 meV). In this work, we demonstrate that the thermoelectric power (TEP) can be used as an effective probe to investigate fine changes in the DOS of BLG. We observed additional entropy features in the vicinity of the charge neutrality point (CNP) in gapped BLG. This apparent violation of the Mott formula can be explained quantitatively by considering the effects of trigonal warping, thereby serving as possible evidence of a Lifshitz transition.
解析态密度（DOS）中的低能特征是理解基于石墨烯的二维异质结构中各种丰富新颖现象的关键。双层石墨烯（BLG）中由三角翘曲引起的里夫希茨转变已在理论和实验上得到证实。然而，由于其相对较低的能量尺度（约1毫电子伏特），在实验中实现其对输运性质的影响一直具有挑战性。在这项工作中，我们证明了热电功率（TEP）可以用作研究BLG的DOS精细变化的有效探针。我们在带隙BLG的电荷中性点（CNP）附近观察到了额外的熵特征。通过考虑三角翘曲的影响，可以定量解释这种对莫特公式的明显违反，从而作为里夫希茨转变的可能证据。
