Generation of pure bulk valley current in graphene
  The generation of valley current is a fundamental goal in graphene valleytronics but no practical ways of its realization are known yet. We propose a workable scheme for the generation of bulk valley current in a graphene mechanical resonator through adiabatic cyclic deformations of the strains and chemical potential in the suspended region. The accompanied strain gauge fields can break the spatial mirror symmetry of the problem within each of the two inequivalent valleys, leading to a fnite valley current due to quantum pumping. An all-electrical measurement configuration is designed to detect the novel state with pure bulk valley currents. 
Yongjin Jiang, Tony Low, Kai Chang, Mikhai I. Katsnelson, and   Francisco Guinea
cond-mat.mes-hall