期刊
PHYSICAL REVIEW B
卷 89, 期 12, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.89.121404
关键词
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资金
- MINECO [PCT-420000-2010-008, JCYL SA226U13, FPU AP2009-2619]
- USAL-Apoyo a la Investigacion KBBB
We report on multiterminal electrical transport measurements performed on a bilayer graphene sheet enclosed by two hexagonal boron nitride flakes. We characterize the temperature dependence of electrical resistivity from 300 mK to 50 K, varying the carrier densities with a back gate. The resistivity curves clearly show a temperature-independent crossing point at density n = n(c) approximate to 2.5 x 10(11) cm(-2) for both positive and negative carriers, separating two distinct regions with dp/dT < 0 and dp/dT > 0, respectively. Our analysis rules out the possibility of a zero-T quantum phase transition, revealing instead the onset of robust ballistic transport forn > n(c), while the T dependence close to the neutrality point is the one expected from the parabolic energy-momentum relation. At low temperature (T << 10 K), the data are compatible with transport via variable range hopping mediated by localized impurity sites, with a characteristic exponent 1/3 that is renormalized to 1/2 by Coulomb interaction in the high-density regime.
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