Yuan Noah F Q, Isobe Hiroki, Fu Liang
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
Nat Commun. 2019 Dec 18;10(1):5769. doi: 10.1038/s41467-019-13670-9.
The van Hove singularity in density of states generally exists in periodic systems due to the presence of saddle points of energy dispersion in momentum space. We introduce a new type of van Hove singularity in two dimensions, resulting from high-order saddle points and exhibiting power-law divergent density of states. We show that high-order van Hove singularity can be generally achieved by tuning the band structure with a single parameter in moiré superlattices, such as twisted bilayer graphene by tuning twist angle or applying pressure, and trilayer graphene by applying vertical electric field. Correlation effects from high-order van Hove singularity near Fermi level are also discussed.
由于动量空间中能量色散的鞍点的存在，态密度中的范霍夫奇点通常存在于周期系统中。我们在二维中引入了一种新型的范霍夫奇点，它由高阶鞍点产生，并表现出幂律发散的态密度。我们表明，通过在莫尔超晶格中用单个参数调节能带结构，通常可以实现高阶范霍夫奇点，例如通过调节扭转角或施加压力来调节扭曲双层石墨烯，以及通过施加垂直电场来调节三层石墨烯。还讨论了费米能级附近高阶范霍夫奇点的关联效应。
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