KITS-IOP-ITP Joint Seminar

Title: Interaction effects and quantum Hall physics in new types of graphene and graphite superlattices

Speaker: Prof. Jianpeng Liu (ShanghaiTech Unversity)
Time: Oct. 9 (Monday), 10:00
Place: Rm M830, IOP-CAS

Abstract: 
In this talk, we discuss interaction effects and quantum Hall physics in two types of graphene and graphite superlattice systems. First, we consider a new type of Coulomb-coupled graphene-insulator heterostructures with gate tunable band alignment. Charge carriers can be transferred between graphene and the substrate under the control of gate voltages. The charge transfer may yield a long-wavelength electronic crystal at the surface of the substrate, which can be significantly stabilized by the interlayer Coulomb coupling. The electronic crystal exerts a superlattice Coulomb potential on the Dirac electrons in graphene, which generates subbands with reduced non-interacting Fermi velocity. As a result, e-e Coulomb interactions within graphene would play a more important role, giving rise to a gapped Dirac state at the charge neutrality point, accompanied by interaction-enhanced Fermi velocity [1]. The latter would lead to robust quantum Hall plateaux under tiny magnetic fields persisting to high temperatures [2].  Second, we explore the physical properties of a new type of three dimensional moire graphite superlattice with homogeneous twist angle, which is grown by in situ chemical vapor decomposition method. When the twist angle is smaller than twice of the magic angle of TBG, there always exist “magic momenta" at which the in-plane Fermi velocities of the moire bands vanish. Topologically distinct flat bands can even co-exist at different “magic momenta” in a single bulk moire graphite superlattice. Most saliently, when the twist angle is relatively large, flat three dimensional Landau levels would emerge in the system, which may give rise to robust three dimensional quantum Hall effects over a large range of twist angles [3].

[1] X. Lu et al. Nat. Commun. 14, 5550 (2023)
[2] Y. Wang et al., Nat. Nanotechnol. 17, 1272 (2022)
[3] X. Lu et al., arXiv:2309.00825

Short bio: 刘健鹏教授于2010年本科毕业于南开大学物理学院，随即前往美国罗格斯大学攻读博士学位，于2015年博士毕业，随后前往UCSB以及香港科大先后担任博士后以及研究助理教授等职位。从2020年5月至今在上海科技大学任研究员以及tenure-track助理教授。刘健鹏教授的研究方向为理论和计算凝聚态物理学，具体包括：摩尔二维超晶格和二维异质结体系的电子结构、相互作用效应、输运和光学性质等方面的理论研究，以及关联金属、磁性拓扑材料等体系的理论研究和第一性原理计算研究等等。

More details can be found in http://seminar.cpsjournals.cn/