Giesbers A J M, Zeitler U, Katsnelson M I, Ponomarenko L A, Mohiuddin T M, Maan J C
High Field Magnet Laboratory, Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
Phys Rev Lett. 2007 Nov 16;99(20):206803. doi: 10.1103/PhysRevLett.99.206803. Epub 2007 Nov 14.
We have measured the quantum-Hall activation gaps in graphene at filling factors nu=2 and nu=6 for magnetic fields up to 32 T and temperatures from 4 to 300 K. The nu=6 gap can be described by thermal excitation to broadened Landau levels with a width of 400 K. In contrast, the gap measured at nu=2 is strongly temperature and field dependent and approaches the expected value for sharp Landau levels for fields B>20 T and temperatures T>100 K. We explain this surprising behavior by a narrowing of the lowest Landau level.
我们测量了石墨烯在填充因子ν = 2和ν = 6时，磁场高达32 T且温度在4至300 K范围内的量子霍尔激活能隙。ν = 6时的能隙可以通过热激发到展宽的朗道能级来描述，展宽宽度为400 K。相比之下，在ν = 2时测量的能隙强烈依赖于温度和磁场，对于磁场B > 20 T且温度T > 100 K时，接近尖锐朗道能级的预期值。我们通过最低朗道能级的变窄来解释这种令人惊讶的行为。
