Topological transport in 2D materials
Topological states of quantum materials offer an exciting platform to test some profound ideas in mathematics and physics. In 2D materials, we achieved to observed topological phases by electrical transport measurement. The first example is a topological valley current in bilayer graphene when the inversion symmetry is broken by an electric field.[1] A second example is topological high order Chern insulator and ferromagnetism in ABC-stacked trilayer graphene on hBN moiré superlattice. By using a electric field, we achieve to tune the topology of the correlated flat band in the moiré superlattice. A high order Chern insulator is observed from the quantized anomalous Hall effect.[2][3]
1.Nature Physics 11 (12), 1027-1031. (2015)
2.Nature, 579, 56–61. (2020)
3.Physical Review Letters, 122, 016401. (2019)
Tunable correlated states and superconductivity in graphene
Tunable Mott insulator and superconductivity in ABC-stacked trilayer graphene on hBN moiré superlattice. For the first time, we experimentally create an ABC-stacked trilayer graphene on hBN moiré superlattice, and acheive the moiré flat band. The bandwidth and correlated strength can be conviniently tuned by the vertical electric field in this system. In the strong correlated regime, we observe the Mott insulating states[4] and signatures of superconductivity[5].
4. Nature, 572, 215–219 . (2019)
5. Nature Physics, 15, 237–241. (2019)
Engineering graphene’s electronic properties by moiré superlattice
Graphene and hBN are both honeycomb lattices with tiny lattice constant mismatch. A long-periodic moiré pattern forms when graphene is put on hBN with a small twisted angle. The moiré pattern can dramatically modify the electronic properties of graphene, such as a band gap opening, secondary and tertary Dirac points from band folding, and Hofstadter butterfly physics.
6. Nano Letters, 17, 3576-3581 . (2017)
7. Nature Materials, 12, 792-797. (2013)
8. Nature Physics, 12, 1111–1115. (2016)
9. Physical Review Letters, 116 (12), 126101. (2016)
10. Nano Letters, 16 (4), 2387-2392. (2016)