Journal
PHYSICAL REVIEW LETTERS
Volume 110, Issue 17, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.110.176802
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Funding
- Spanish MICINN [FIS2010-21883, FIS2011-23488, CONSOLIDER CSD2007-0010]
- Generalitat Valenciana [ACCOMP/2012/127, PROMETEO/2012/011]
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We report electrical conductance measurements of Bi nanocontacts created by repeated tip-surface indentation using a scanning tunneling microscope at temperatures of 4 and 300 K. As a function of the elongation of the nanocontact, we measure robust, tens of nanometers long plateaus of conductance G(0) = 2e(2)/h at room temperature. This observation can be accounted for by the mechanical exfoliation of a Bi(111) bilayer, a predicted quantum spin Hall (QSH) insulator, in the retracing process following a tip-surface contact. The formation of the bilayer is further supported by the additional observation of conductance steps below G(0) before breakup at both temperatures. Our finding provides the first experimental evidence of the possibility of mechanical exfoliation of Bi bilayers, the existence of the QSH phase in a two-dimensional crystal, and, most importantly, the observation of the QSH phase at room temperature. DOI: 10.1103/PhysRevLett.110.176802
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