Unconventional quantum Hall effect and Berry's phase of 2π in bilayer graphene
Unconventional quantum Hall effect and Berry's phase of 2π in bilayer graphene
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DOI：
10.1038/nphys245
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发表时间：
2006-03-01
期刊：
影响因子：
19.6
通讯作者：
Geim, AK
中科院分区：
文献类型：
--
作者：
Novoselov, KS;McCann, E;Geim, AK
整数量子霍尔效应有两种已知的不同类型。一种是传统的量子霍尔效应，这是二维半导体系统的特征，另一种是在石墨烯中观察到的相对论对应物，其中电荷载流子模仿以贝里相位π为特征的狄拉克费米子，这导致霍尔平台位置发生偏移,,,,,,。在这里，我们报告了第三种整数量子霍尔效应。双层石墨烯中的电荷载流子具有抛物线能谱，但具有手性，并且显示贝瑞相 2π 影响其量子动力学。这些费米子的朗道量子化导致霍尔电导率在标准整数位置出现平台，但最后一个（零级）平台缺失。零级异常伴随着低浓度和高磁场限制下的金属导电性，与该区域中的传统绝缘行为形成鲜明对比。所揭示的手性费米子没有已知的类似物，并且为量子力学研究提供了一个有趣的案例。
There are two known distinct types of the integer quantum Hall effect. One is the conventional quantum Hall effect, characteristic of two-dimensional semiconductor systems,, and the other is its relativistic counterpart observed in graphene, where charge carriers mimic Dirac fermions characterized by Berry’s phaseπ, which results in shifted positions of the Hall plateaus,,,,,,. Here we report a third type of the integer quantum Hall effect. Charge carriers in bilayer graphene have a parabolic energy spectrum but are chiral and show Berry’s phase 2πaffecting their quantum dynamics. The Landau quantization of these fermions results in plateaus in Hall conductivity at standard integer positions, but the last (zero-level) plateau is missing. The zero-level anomaly is accompanied by metallic conductivity in the limit of low concentrations and high magnetic fields, in stark contrast to the conventional, insulating behaviour in this regime. The revealed chiral fermions have no known analogues and present an intriguing case for quantum-mechanical studies.