Composite fermions and broken symmetries in graphene

被引：94

作者：

Amet, F. ^{[1
]}

Bestwick, A. J. ^{[2
]}

Williams, J. R. ^{[2
]}

Balicas, L. ^{[3
]}

Watanabe, K. ^{[4
]}

Taniguchi, T. ^{[4
]}

Goldhaber-Gordon, D. ^{[1
,2
]}

机构：

[1] Stanford Univ, Dept Appl Phys, Stanford, CA 94305 USA

[2] Stanford Univ, Dept Phys, Stanford, CA 94305 USA

[3] Natl High Magnet Field Lab, Tallahassee, FL 32310 USA

[4] Natl Inst Mat Sci, Adv Mat Lab, Tsukuba, Ibaraki 3050044, Japan

来源：

NATURE COMMUNICATIONS | 2015年 / 6卷

基金：

美国国家科学基金会;

关键词：

DIRAC FERMIONS; BORON-NITRIDE; QUANTUM; INTEGER; PHASE; SPIN;

D O I：

10.1038/ncomms6838

中图分类号：

O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];

学科分类号：

07 ; 0710 ; 09 ;

摘要：

The electronic properties of graphene are described by a Dirac Hamiltonian with a four-fold symmetry of spin and valley. This symmetry may yield novel fractional quantum Hall (FQH) states at high magnetic field depending on the relative strength of symmetry-breaking interactions. However, observing such states in transport remains challenging in graphene, as they are easily destroyed by disorder. In this work, we observe in the first two Landau levels the two-flux composite-fermion sequences of FQH states between each integer filling factor. In particular, the odd-numerator fractions appear between filling factors 1 and 2, suggesting a broken-valley symmetry, consistent with our observation of a gap at charge neutrality and zero field. Contrary to our expectations, the evolution of gaps in a parallel magnetic field suggests that states in the first Landau level are not spin-polarized even up to very large out-of-plane fields.

引用

页数：7

共 58 条

[31] Electron-hole asymmetric integer and fractional quantum Hall effect in bilayer graphene [J].