Recent experiments by Guti\'errez et al. [Nature Phys. 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.
@article{arxiv.1708.08348,
title = {Valley-momentum locking in a graphene superlattice with Y-shaped Kekul\'e bond texture},
author = {O. V. Gamayun and V. P. Ostroukh and N. V. Gnezdilov and İ. Adagideli and C. W. J. Beenakker},
journal= {arXiv preprint arXiv:1708.08348},
year = {2018}
}