Halfinteger quantum hall effect singlelayer graphene. Quantum hall effects in graphene 55, 56 have been studied intensively. We also show that strained superlattices can be used to open significant energy gaps in graphenes electronic spectrum. Quantum hall effects in monolayerbilayer graphene planar. Experimental observation of the quantum hall effect and berry.
The qhe is exclusive to twodimensional 2d metals and has elucidated many important aspects of quantum physics and deepened our understanding of interacting systems. Quantum hall resistance standards from graphene grown by chemical vapour deposition on silicon carbide. Experimental observation of the quantum hall effect and berrys phase in graphene yuanbo zhang1, yanwen tan1, horst l. Graphene electromechanics in the quantum hall regime 28 dual top gated graphene transistor in the quantum hall regime 29 we will begin by providing an introduction to the thesis in chapter 1. Qhe plateaus observed at landau level spectrum with very high cyclotron energy k bilayer novoselov et al, 2005, zhang et al, 2005 manifestation of relativistic dirac electron properties 42x2 spin and valley degeneracy recently.
Nov 10, 2005 when electrons are confined in twodimensional materials, quantum mechanically enhanced transport phenomena such as the quantum hall effect can be observed. Abastacked trilayer graphene is a unique 2d electron system with mirror re. We explain why graphene and bilayer graphene can be viewed respectively as j1 and j2 chiral twodimensional electron gases c2degs, and why this. Quantum hall effect in graphene with superconducting. Mathematical, physical and engineering sciences, 2010, pp. Fractional quantum hall effect in suspended graphene probed with twoterminal measurements, philosophical transactions of the royal society a. Halfinteger quantum hall effect in graphene exceptionally high mobility graphene samples allow us to investigate transport phenomena in the magnetic quantum limit where the qhe manifests itself.
Yang, wanxiang feng,2 wangkong tse,1 jun ding,2 yugui yao,2,1, jian wang,3 and qian niu1 1department of physics, the university of texas, austin, texas 78712, usa 2beijing national laboratory for condensed matter physics and institute of physics, chinese. Pdf quantum hall effect in graphene with superconducting. Three dimensional generalization topological insulator, surface states. The qhe is a fascinating macroscopic quantum effect occurring in twodimensional conductors and relates the resistance quantum, he2, only to the fundamental constants of nature, h, the planck constant. The quantum hall effect in graphene physics drexel university.
The quantum hall qh effect in twodimensional electron and hole gas is studied in high quality graphene samples. Quantum hall effect and quantum point contact in bilayer. Quantum spin hall effect in graphene university of illinois. Unconventional quantum hall effect in graphene university of. Quantum spin hall effect spin orbit induced energy gap in graphene. Broken symmetry quantum hall states in dualgated aba trilayer graphene yongjin lee, jairo velasco, jr, david tran, fan zhang, w. Lowenergy transport measurements in quantum hall systems have been argued to be governed by emergent modular symmetries whose predictions are robust against many of the detailed microscopic dynamics. A quantum spin hall effect is seen in graphene with the spinorbit term included.
Experiment results the quantum hall effect qhe is one example of a quantum phenomenon that occurs on a truly macroscopic scale. Here, we report a class of quantum hall effect, the quantum parity hall qph effect, in which boundary. Energy gaps and a zerofield quantum hall effect in graphene. The recent quantum hall experiments in graphene have confirmed the theoretically wellunderstood picture of the quantum hall qh conductance in fermion systems with continuum dirac spectrum. A general description of graphene, its electrical and mechanical properties and various other concepts related to the experiment will be given in. Quantum hall effect in graphene with twisted bilayer. Quantum hall effect in carbon nanotubes and curved graphene strips.
Pdf quantum hall effect in carbon nanotubes and curved. Unconventional quantum hall effect and berrys phase of 2. We also show that strained superlattices can be used to open significant energy gaps. Pdf quantum hall effect and the topological number in. Graphenebased quantum hall effect metrology mrs bulletin. Roomtemperature quantum hall effect in graphene arxiv.
We ascribe this enhanced quantum hall plateau conductance to. The quantum hall effect, which is characterized by an insulating bulk and chiral edge states, has recently been generalized from transport of charges to transport of other degrees of freedom, leading to quantum spin hall and quantum valley hall effects. The first four chapters require only basic quantum mechanics. Graphene, the quantum spin hall effect and topological insulators i. The quantum hall effect qhe, one example of a quantum phenomenon that occurs on a truly macroscopic scale, has been attracting intense interest since its. Request pdf quantum hall effect in graphene the quantum hall qh effect in twodimensional electron and hole gas is studied in high. We present lowtemperature transport measurements on dualgated suspended trilayer graphene in the quantum hall qh regime. Below their upper critical field of 4 t, an integer quantum hall effect coexists with superconductivity in the leads but with a plateau conductance that is larger than in the normal state. The unique halfinteger quantum hall effect qhe in monolayer graphene serves as a. May 21, 2019 the quantum hall effect, which is characterized by an insulating bulk and chiral edge states, has recently been generalized from transport of charges to transport of other degrees of freedom, leading to quantum spin hall and quantum valley hall effects. The quantum hall effect qhe, one example of a quantum phenomenon that occurs on a truly macroscopic scale, has been attracting intense interest since its discovery in 1980 1.
Energy gaps and a zerofield quantum hall effect in graphene by. Roomtemperature quantum hall effect in graphene science. The discovery of the josephson effect and the integer quantum hall effect qhe led to the realization of reproducible and universal voltage and resistance standards directly linked to plancks constant and the electron charge. Quantum parity hall effect in bernalstacked trilayer graphene. Graphene, showing fascinating characteristics of the quantum hall effect at room temperature, extremely high carrier mobility, ambipolar field effect, and sensitive response to single molecules, has become one of the hottest research topics in recent years. Energy gaps and a zerofield quantum hall effect in. Although, the conclusive evidence for collective behaviour of electrons in graphene is lacking so far, recently scientists have observed the fractional quantum hall effect fqhe in graphene experimentally. Disappointingly, however, the qhe has been observed only at liquid. Precision comparison of the quantum hall effect in graphene. The quantum hall effect qhe, one example of a quantum phenomenon that occurs on a truly macroscopic scale, has attracted intense interest since its discovery in 1980 and has helped elucidate many important aspects of quantum physics. In the past few decades, major improvements in electrical standards have come from quantum solidstate physics. From quantum hall effect in graphene to chiral asymmetry in qed by lifang xia a dissertation presented in partial ful. Spin hall effect is the accumulation of spin on the boundaries.
Evidence for a quantum spin hall phase in graphene. Pdf roomtemperature quantum hall effect in graphene. Quantum hall effect in graphene international journal of. Hall effect and a nonzero berrys phase have been discovered in graphene. Yang, wanxiang feng,2 wangkong tse,1 jun ding,2 yugui yao,2,1, jian wang,3 and qian niu1 1department of physics, the university of texas, austin, texas 78712, usa. The integer quantum hall effect qhe was discovered by k. Pdf quantum hall effect in hydrogenated graphene richard. The spin hall effect is the accumulation of spin on boundaries the hall effect has electrons accumulated on the boundaries. Graphenes exceptionally weak spinorbit couplingstemming from carbons low massposes the primary obstacle. We propose the recentlyobserved quantum hall effect in graphene as a test of these ideas, and identify to this end a class of predictions for graphene which would follow from the same modular.
Quantum anomalous hall effect in graphene from rashba and. Observation of the fractional quantum hall effect in graphene arxiv. The discovery seven years ago of the quantum hall effect qhe in graphene sparked an immediate interest in the metrological community 1,2. Broken symmetry quantum hall states in dualgated aba. Pdf quantum hall effect and the topological number in graphene. Helical quantum hall phase in graphene on srtio3 science. Evidence for a quantum spin hall phase in graphene decorated. We numerically calculate the hall conductivity in a single landau level with disorder, and estimate the critical energies for the extended states in thermodynamic limit. Igor shovkovy, chair richard lebed kevin schmidt easson damien. However, unlike in the standard case, this latter quantity is. The quantum hall effect or integer quantum hall effect is a quantummechanical version of the hall effect, observed in twodimensional electron systems subjected to low temperatures and strong magnetic fields, in which the hall conductance.
Quantum hall effect in graphene request pdf researchgate. Fractional quantum hall effect in suspended graphene. Pdf the quantum hall effect qhe, one example of a quantum phenomenon that occurs on a truly macroscopic scale, has attracted intense interest since. Its unconventional landau level spectrum of massless dirac fermions leads to a new type of integer quantum hall effect iqhe known as halfinteger quantum. Here, we report a class of quantum hall effect, the quantum parity hall qph effect, in which boundary channels are distinguished by even or. Previous studies have demonstrated that slg shows halfinteger quantum hall effects.
Quantum hall effect in a 2deg quantum hall effect in graphene summary how to produce a 2deg qhe by solving the schrodinger equation experimental results qhe described by the dirac equation the anomalous integer qhe experimental results 2. A new 2d electronic phase gapless edge states and transport time reversal symmetry and z 2 topological stability. Readers are referred to chapter 4 for the basic concepts of quantum hall effects in semiconductors, e. Related content precision comparison of the quantum hall effect in graphene and gallium arsenide t j b m janssen, j m williams, n e. The quantum hall effect in graphene university of konstanz. Jan 14, 2008 halfinteger quantum hall effect singlelayer graphene. This is a course on the quantum hall effect, given in tifr, mumbai. Here we report a third type of the integer quantum hall effect. Quantum hall effect in graphene with superconducting electrodes. Sep 27, 2009 we suggest realistic ways of creating this quantum state and observing the pseudomagnetic quantum hall effect. In this paper we take into account the lattice and perform an exact diagonalization of the landau problem on the hexagonal lattice. Quantum anomalous hall effect in graphene from rashba and exchange effects zhenhua qiao, 1shengyuan a. We experimentally and theoretically study artificially enhanced spinorbit.
The integer quantum hall effect is studied for a noninteracting electron in a monolayer graphene. The signature of qhe is the quantization plateaus in the hall resistance rxy and vanishing magnetoresistance rxx in a magnetic field. The properties of graphene, a single atomic layer of graphite 1, have attracted great interest, especially after the experimental discovery 2,3 and made independently theoretical prediction 46 of an anomalous quantization in the quantum hall qh effect. We numerically calculate the hall conductivity in a single landau level with disorder, and. Charge carriers in bilayer graphene have a parabolic energy spectrum but are. Experimental observation of the quantum hall effect and. Geim1 t he quantum hall effect qhe, one example of a quantum phenomenon that occurs on a truly macroscopic scale, has been attracting intense interest since. Precision comparison of the quantum hall effect in. Quantum hall effect an overview sciencedirect topics. Qhe, where the hall resistance is quantized at values of rxyh. Generally speaking, the iqhe in graphene has the same underlying mechanism as that in the semiconductor 2deg. We explain why graphene and bilayer graphene can be viewed respectively as j1 and j2 chiral twodimensional electron gases c2degs, and why.
We have observed the wellkown quantum hall effect qhe in epitaxial graphene grown on silicon carbide sic by using, for the first time. It may provide a starting point for the search for other spin hall insulators in twodimensional or in layered. We experimentally and theoretically study artificially enhanced spinorbit coupling in graphene via random. Recent discoveries of the quantum anomalous hall effect, which breaks timereversal symmetry, and quantum spin halltopological insulators are also variants of the qhe in terms of topology. Landau levels, cyclotron frequency, degeneracy strength, flux quantum. Quantum hall e ect and electromechanics in graphene. It has also led to the establishment of a new metrological standard, the resistance quantum. Graphene, universality of the quantum hall effect and. When electrons are confined in twodimensional materials, quantummechanically enhanced transport phenomena such as the quantum hall effect can be observed. Realization of the quantum spin hall effect in graphene devices has remained an outstanding challenge dating back to the inception of the field of topological insulators.
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