Generation of Pure Bulk Valley Current in Graphene

Y. J. and K. C. acknowledge the support from the National Natural Science Foundation of China [under Grants No. 11004174 (Y. J.) and No. 10934007 (K. C.)]. Y. J. is also supported by the Program for Innovative Research Team in Zhejiang Normal University. K. C. is also supported by the National Basic Research Program of China (973 Program) under Grant No. 2011CB922204. T. L. also acknowledges partial support from NRIINDEX. M. I. K. acknowledges financial support from FOM, Netherlands. F. G. acknowledges financial support from Spanish MICINN (Grants No. FIS2008-00124, No. FIS2011-23713, and No. CONSOLIDER CSD2007- 00010), and ERC, Grant No. 290846.