Spin-Polarized Nematic Order, Quantum Valley Hall States, and Field-Tunable Topological Transitions in Twisted Multilayer Graphene Systems

We investigate the structure of gapless edge modes propagating at the boundary of some fractional quantum Hall states. We show how to deduce explicit trial wavefunctions from the knowledge of the effective theory governing the edge modes. In general, quantum Hall states have many edge states. Here, we discuss the case of fractions having only two such modes. The case of spin-polarized and spin-singlet states at filling fraction ν = 2/5 is considered. We give an explicit description of the decoupled charged and neutral modes. Then we discuss the situation involving negative flux acting on the composite fermions. This happens notably for the filling factor ν = 2/3 which supports two counterpropagating modes. Microscopic wavefunctions for spin-polarized and spin-singlet states at this filling factor are given. Finally, we present an analysis of the edge structure of a non-Abelian state involving also negative flux. Counterpropagating modes involve, in all cases, explicit derivative operators diminishing the angular momentum of the system.

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Some peculiarities of thermopower at the Lifshitz topological transitions due to stacking change in bilayer and multilayer graphene

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2019.0028 ◽

2019 ◽

Vol 475 (2226) ◽

pp. 20190028 ◽

Cited By ~ 1

Author(s):

V. N. Davydov

Keyword(s):

Seebeck Coefficient ◽

Electronic Properties ◽

Chemical Potential ◽

Bilayer Graphene ◽

Multilayer Graphene ◽

Gapped Graphene ◽

Topological Transitions

Singularities of thermopower (the Seebeck coefficient) are considered at the Lifshitz topological transitions (LTT) in bilayer graphene (BLG) and multilayer graphene (MLG) due to stacking change from AB to AA . The dependence of singularities on μ , γ 1 and Δ is investigated ( μ is the chemical potential, γ 1 is the interlayer hopping parameter and Δ is the gap value) for the gapped graphene, as well as for the gapless one. The present paper results indicate that effects of the thermopower singularities are appreciable and can be used to observe the LTT, and to explore the degree of stacking change from AB to AA in graphene. Therefore, the thermopower singularities at LTT due to stacking change from AB to AA can be used as a powerful tool to control electronic properties of BLG- and MLG-based structures.

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Application of Fermi hypernetted-chain theory to spin-polarized higher-order fractional quantum Hall states

Physical Review B ◽

10.1103/physrevb.95.155109 ◽

2017 ◽

Vol 95 (15) ◽

Author(s):

J. W. Kim ◽

H. Kim ◽

N. Kim

Keyword(s):

Quantum Hall ◽

Higher Order ◽

Fractional Quantum ◽

Fractional Quantum Hall ◽

Quantum Hall States ◽

Spin Polarized ◽

Hypernetted Chain ◽

Chain Theory ◽

Hall States

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Spin-polarized Scanning Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100176976 ◽

1990 ◽

Vol 48 (4) ◽

pp. 768-769

Author(s):

Kazuyuki Koike ◽

Hideo Matsuyama

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

High Speed ◽

Magnetic Thin Films ◽

Electron Spin Polarization ◽

Acquisition Time ◽

Magnetization Direction ◽

Spin Polarized ◽

Conventional Methods ◽

Scanning Electron

Spin-polarized scanning electron microscopy (spin SEM), where the secondary electron spin polarization is used as the image signal, is a novel technique for magnetic domain observation. Since its first development by Koike and Hayakawa in 1984, several laboratories have extensively studied this technique and have greatly improved its capability for data extraction and its range of applications. This paper reviews the progress over the last few years.Almost all the high expectations initially held for spin SEM have been realized. A spatial resolution of several hundreds angstroms has been attained, which is nearly one order of magnitude higher than that of conventional methods for thick samples. Quantitative analysis of magnetization direction has been performed more easily than with conventional methods. Domain observation of the surface of three-dimensional samples has been confirmed to be possible. One of the drawbacks, a long image acquisition time, has been eased by combining highspeed image-signal processing with high speed scanning, although at the cost of image quality. By using spin SEM, the magnetic structure of a 180 degrees surface Neel wall, magnetic thin films, multilayered films, magnetic discs, etc., have been investigated.

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