Abstract

Over the past half-century, exciton  insulators have been observed in various experimental systems,  predominantly through indirect spectroscopic studies. However, there  is a notable lack of studies on the electrical transport and  gate-tuning of this correlated insulator. The main reason for this  limitation is the difficulty in controlling the strength of electron  correlations in semi-metallic systems (or narrow bandgap  semiconductors) near charge neutrality.

In this talk, we show that by bringing  Bernal-stacked bilayer graphene (BLG) into contact with a few-layered  insulator CrOCl, the resulted vertical heterostructures can give rise  to an extraordinarily robust ground state of insulator at the charge  neutrality [1]. This emerged band-gap is of quantum origin, and can be  controlled by in-plane electric fields, vertical electric fields,  temperature, and carrier density.

Based on this correlated insulating  state, both N-type and P-type transistors are achieved. Further,  CMOS-like semiconducting BLG logic inverter with a gain of  approximately 1.2 (yet to be improved) at a temperature of 1.5 K at an  input voltage of 0.2 V can be realized. This could be a crucial step  forward for future carbon computing.

Unlike the conventional approaches based  on intrinsic band gaps and doping principles in silicon-based  semiconductors and two-dimensional semiconductors, the route of  quantum-origin correlated gapped state employed in this study breaks  new ground. It constructs long-range charge order at the interface by  utilizing interface coupling and then leverages the interface states  to influence electronic correlations in graphene. This coupling  mechanism represents a universal control method and holds the  potential for discovering intriguing physical phenomena in a broader  range of two-dimensional electron systems [2].

References

[1] K. N. Yang, X. Gao, Y. Wang, T.  Zhang, et al, Nat. Commun., 14, 2136 (2023).

[2] X. Lu, et al., Nat. Commun., 14,  5550 (2023).

报告人简介：

韩拯教授在新原理低维量子器件等方面取得系列进展：演示了本征二维磁性半导体自旋场效应管（Nat.  Nanotechnol., 13, 554, 2018）；发现了门电压可调的二维巨各向异性电阻效应（Nat. Nanotechnol.,  10, 2302, 2019）；制备的达到物理极限的单原子层亚纳米鳍片宽度FinFET 鳍栅晶体管（Nat. Commun., 11,  1205, 2020）入选《半导体学报》“中国半导体十大进展”；揭示了双重对齐莫尔超晶格中弱相互作用下的关联绝缘态（Nat.  Commun., 12, 7196,  2021）；发展了一种界面电荷序调控二维电子气关联效应的新方法，实现了极具鲁棒性量子霍尔态，液氮温度获得量子化边界导电态只需要0.35  T磁场，为目前的世界记录（Nat. Nanotechnol., 17, 1272, 2022）。韩拯教授先后入选国家级海外青年人才计划、国家级特殊人才支持计划；曾获“山西省五四青年奖章”、“山西省五一劳动奖章”、“MIT科技评论中国区35岁以下创新35人”等荣誉。