近日，美国康奈尔大学的Kin Fai Mak&Jie Shan及其研究小组取得一项新进展。经过不懈努力，他们实现二维电子化学势的光学读出。相关研究成果已于2024年1月26日在国际知名学术期刊《自然—光子学》上发表。
本文报道了一种光学读出技术，用于测量任意二维材料的化学势μ。该技术采用单层半导体传感器，通过电容耦合与样品相连。传感器的光学响应决定了将其化学势固定在带边缘的偏置，并直接读取样品的μ值。研究人员在AB堆叠的MoTe2/WSe2莫尔双层中演示了该技术。通过交流读出，得到直流灵敏度约为20μeVHz-1/2的μ值，以及可压缩性和层间电极化。
结果表明，当掺杂密度为1个空穴/莫尔晶胞时，随着面外电场的增大，材料的绝缘态由莫特绝缘体演变为电荷转移绝缘体。此外，研究人员对μ进行成像并量化样品的空间不均匀性。这项研究工作为二维量子材料热力学性质的高空间分辨率和高时间分辨率测量打开了大门。
据悉，据悉，电子系统的化学势(μ)是固体的基本性质。μ的精确测量对于理解电子相互作用和物质的量子态起着至关重要的作用。然而，由于样品体积小，背景信号大，微纳米尺度样品的热力学测量具有挑战性。
附：英文原文
Title: Optical readout of the chemical potential of two-dimensional electrons
Author: Xia, Zhengchao, Zeng, Yihang, Shen, Bowen, Dery, Roei, Watanabe, Kenji, Taniguchi, Takashi, Shan, Jie, Mak, Kin Fai
Issue&Volume: 2024-01-26
Abstract: The chemical potential (μ) of an electron system is a fundamental property of a solid. A precise measurement of μ plays a crucial role in understanding the electron interaction and quantum states of matter. However, thermodynamics measurements in micro- and nanoscale samples are challenging because of the small sample volume and large background signals. Here we report an optical readout technique for μ of an arbitrary two-dimensional material. A monolayer semiconductor sensor is capacitively coupled to the sample. The sensor optical response determines a bias that fixes its chemical potential to the band edge and directly reads the μ value of the sample. We demonstrate the technique in AB-stacked MoTe2/WSe2 moiré bilayers. We obtain the μ value with a d.c. sensitivity of about 20μeVHz–1/2 and the compressibility and interlayer electric polarization using a.c. readout. The results reveal a correlated insulating state at a doping density of one hole per moiré unit cell, which evolves from a Mott insulator to a charge-transfer insulator with an increasing out-of-plane electric field. Furthermore, we image μ and quantify the spatial inhomogeneity of the sample. Our work opens the door for high-spatial-resolution and high-temporal-resolution measurements of the thermodynamic properties of two-dimensional quantum materials.
DOI: 10.1038/s41566-024-01377-3
Source: https://www.nature.com/articles/s41566-024-01377-3