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Valley-momentum locking in a graphene superlattice with Y-shaped Kekulé bond texture

2018; IOP Publishing; Volume: 20; Issue: 2 Linguagem: Inglês

10.1088/1367-2630/aaa7e5

1367-2630

Oleksandr Gamayun, Viacheslav Ostroukh, N. V. Gnezdilov, İnanç Adagideli, C. W. J. Beenakker,

Quantum and electron transport phenomena

Recent experiments by Guti\'errez $\textit{et al.}$ [Nature Phys. $\textbf{12}$, 950 (2016)] on a graphene-copper superlattice have revealed an unusual Kekul\'e bond texture in the honeycomb lattice --- a Y-shaped modulation of weak and strong bonds with a wave vector connecting two Dirac points. We show that this so-called "Kek-Y" texture produces two species of massless Dirac fermions, with valley isospin locked parallel or antiparallel to the direction of motion. In a magnetic field $B$ the valley degeneracy of the $B$-dependent Landau levels is removed by the valley-momentum locking --- but a $B$-independent and valley-degenerate zero-mode remains.