We explain why graphene and bilayer graphene can be viewed respectively as j1 and j2 chiral twodimensional electron gases c2degs, and why. 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. This is a course on the quantum hall effect, given in tifr, mumbai. 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. Quantum hall effect in graphene request pdf researchgate. Precision comparison of the quantum hall effect in.
From quantum hall effect in graphene to chiral asymmetry in qed by lifang xia a dissertation presented in partial ful. Jan 14, 2008 halfinteger quantum hall effect singlelayer graphene. Quantum hall effect an overview sciencedirect topics. Graphenebased quantum hall effect metrology mrs bulletin. It has also led to the establishment of a new metrological standard, the resistance quantum. A quantum spin hall effect is seen in graphene with the spinorbit term included. 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.
We numerically calculate the hall conductivity in a single landau level with disorder, and. Graphenes exceptionally weak spinorbit couplingstemming from carbons low massposes the primary obstacle. The quantum hall qh effect in twodimensional electron and hole gas is studied in high quality graphene samples. Quantum spin hall effect spin orbit induced energy gap in graphene. The integer quantum hall effect is studied for a noninteracting electron in a monolayer graphene. We have realized an integer quantum hall system with superconducting contacts by connecting graphene to niobium electrodes.
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. 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. Nov 10, 2005 when electrons are confined in twodimensional materials, quantum mechanically enhanced transport phenomena such as the quantum hall effect can be observed. 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. We have observed the wellkown quantum hall effect qhe in epitaxial graphene grown on silicon carbide sic by using, for the first time. The spin hall effect is the accumulation of spin on boundaries the hall effect has electrons accumulated on the boundaries. In the past few decades, major improvements in electrical standards have come from quantum solidstate physics. 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.
Related content precision comparison of the quantum hall effect in graphene and gallium arsenide t j b m janssen, j m williams, n e. Precision comparison of the quantum hall effect in graphene. The qhe is exclusive to twodimensional 2d metals and has elucidated many important aspects of quantum physics and deepened our understanding of interacting systems. 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. Quantum hall effect in epitaxial graphene with permanent. Disappointingly, however, the qhe has been observed only at liquid. 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.
Hall effect and a nonzero berrys phase have been discovered in graphene. The unique halfinteger quantum hall effect qhe in monolayer graphene serves as a. Evidence for a quantum spin hall phase in graphene decorated. Experimental observation of the quantum hall effect and berry. Pdf quantum hall effect in twisted bilayer graphene. We find that in an experimentally accessible low temperature regime the symmetry allowed spin orbit potential converts graphene from an ideal twodimensional semimetallic state to a quantum spin hall insulator. Here we report a third type of the integer quantum hall effect. Here, we report a class of quantum hall effect, the quantum parity hall qph effect, in which boundary channels are distinguished by even or.
Graphene, the quantum spin hall effect and topological insulators i. Helical quantum hall phase in graphene on srtio3 science. Halfinteger quantum hall effect singlelayer graphene. Pdf quantum hall effect and the topological number in graphene. We suggest realistic ways of creating this quantum state and observing the pseudomagnetic quantum hall effect. 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. Generally speaking, the iqhe in graphene has the same underlying mechanism as that in the semiconductor 2deg. Quantum hall effects in graphene 55, 56 have been studied intensively. We explain why graphene and bilayer graphene can be viewed respectively as j1 and j2 chiral twodimensional electron gases c2degs, and why this. The quantum hall effect in graphene university of konstanz. Quantum anomalous hall effect in graphene from rashba and. Roomtemperature quantum hall effect in graphene arxiv.
Unconventional quantum hall effect in graphene university of. Quantum hall effect in carbon nanotubes and curved graphene strips. 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. The quantum hall effect in graphene physics drexel university. 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. 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.
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 integer quantum hall effect qhe was discovered by k. Experiment results the quantum hall effect qhe is one example of a quantum phenomenon that occurs on a truly macroscopic scale. A general description of graphene, its electrical and mechanical properties and various other concepts related to the experiment will be given in.
Quantum hall effects in monolayerbilayer graphene planar. Igor shovkovy, chair richard lebed kevin schmidt easson damien. 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. Mathematical, physical and engineering sciences, 2010, pp. 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. We study the effects of spin orbit interactions on the low energy electronic structure of a single plane of graphene. Abastacked trilayer graphene is a unique 2d electron system with mirror re. Quantum spin hall effect in graphene university of illinois. Charge carriers in bilayer graphene have a parabolic energy spectrum but are.
Quantum hall effect in graphene with superconducting. Request pdf quantum hall effect in graphene the quantum hall qh effect in twodimensional electron and hole gas is studied in high. Quantum hall effect in graphene with superconducting electrodes. Fractional quantum hall effect in suspended graphene. We experimentally and theoretically study artificially enhanced spinorbit. Graphene, universality of the quantum hall effect and. Broken symmetry quantum hall states in dualgated aba. Pdf roomtemperature quantum hall effect in graphene. 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. It may provide a starting point for the search for other spin hall insulators in twodimensional or in layered. When electrons are confined in twodimensional materials, quantummechanically enhanced transport phenomena such as the quantum hall effect can be observed. Quantum hall effect in graphene with twisted bilayer.
Experimental observation of the quantum hall effect and berrys phase in graphene yuanbo zhang1, yanwen tan1, horst l. We present lowtemperature transport measurements on dualgated suspended trilayer graphene in the quantum hall qh regime. Pdf quantum hall effect in carbon nanotubes and curved. Quantum hall resistance standards from graphene grown by chemical vapour deposition on silicon carbide. 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 exchange effects zhenhua qiao, 1shengyuan a. Quantum parity hall effect in bernalstacked trilayer graphene. Here, we report a class of quantum hall effect, the quantum parity hall qph effect, in which boundary. Quantum hall effect in graphene international journal of.
Three dimensional generalization topological insulator, surface states. Broken symmetry quantum hall states in dualgated aba trilayer graphene yongjin lee, jairo velasco, jr, david tran, fan zhang, w. Pdf quantum hall effect in hydrogenated graphene richard. Pdf quantum hall effect in graphene with superconducting. Qhe, where the hall resistance is quantized at values of rxyh. Its unconventional landau level spectrum of massless dirac fermions leads to a new type of integer quantum hall effect iqhe known as halfinteger quantum. 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. Unconventional quantum hall effect and berrys phase of 2. Pdf the quantum hall effect qhe, one example of a quantum phenomenon that occurs on a truly macroscopic scale, has attracted intense interest since. Landau levels, cyclotron frequency, degeneracy strength, flux quantum. Evidence for a quantum spin hall phase in graphene. Energy gaps and a zerofield quantum hall effect in. 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.
We also show that strained superlattices can be used to open significant energy gaps. Fractional quantum hall effect in suspended graphene probed with twoterminal measurements, philosophical transactions of the royal society a. 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. Spin hall effect is the accumulation of spin on the boundaries. Pdf quantum hall effect and the topological number in. We also show that strained superlattices can be used to open significant energy gaps in graphenes electronic spectrum.
The first four chapters require only basic quantum mechanics. Previous studies have demonstrated that slg shows halfinteger quantum hall effects. Energy gaps and a zerofield quantum hall effect in graphene by. Quantum hall effect and quantum point contact in bilayer. 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. A new 2d electronic phase gapless edge states and transport time reversal symmetry and z 2 topological stability. 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. Observation of the fractional quantum hall effect in graphene arxiv.
Readers are referred to chapter 4 for the basic concepts of quantum hall effects in semiconductors, e. 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. Quantum hall e ect and electromechanics in graphene. Roomtemperature quantum hall effect in graphene science. However, unlike in the standard case, this latter quantity is. Energy gaps and a zerofield quantum hall effect in graphene. The discovery seven years ago of the quantum hall effect qhe in graphene sparked an immediate interest in the metrological community 1,2.