NANO LETTERS

SHAO Y, LIU ZL, CHENG C, WU X, LIU H, LIU C, WANG JO, ZHU SY, WANG YQ, SHI DX, IBRAHIM K, SUN JT, WANG YL, GAO HJ

PHYSICAL REVIEW LETTERS

REN JD, GUO HM, PAN JB, ZHANG YF, YANG YF, WU X, DU SX, OUYANG M, GAO HJ