Strongly bound excitons in gapless two-dimensional structures

Yufeng Liang,1 Ryan Soklaski,1 Shouting Huang,1 Matthew W. Graham,2 Robin Havener,3 Jiwoong Park,4,5 and Li Yang1,* 1Department of Physics, Washington University in St. Louis, St. Louis, Missouri 63130, USA 2Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA 3School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA 4Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA 5Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA (Received 13 January 2014; published 15 September 2014)