The basics are described well but theres nothing about chernsimons theories or the importance of the edge modes. Katsuaki sato is professor emeritus at tokyo university of agriculture and technology tuat, japan and a program officer of the presto project nextgeneration innovative devices, japan science and technology agency. Graphene, the quantum spin hall effect and topological insulators i. In 1988, it was proposed that there was quantum hall effect without landau levels. Quantum spin hall effect edge modes at the boundary between free space and any.
For sufficiently strong magnetic fields, each landau level may have so many states that all of the free electrons in the system sit in only a few landau levels. There is also a new concept of the quantum spin hall effect which is an analogue of the quantum hall effect, where spin currents flow instead of charge currents. In the new study, researchers bring together one of physics most venerable set of equations those of james clerks. Work supported in part by us department of energy contract deac0276sf00515. Quantum spin hall effect and topological phase transition in hgtequantum wells taylor l.
The search for topological states of matter that do not require magnetic fields for their observation led to the theoretical prediction in 2006 and experimental observation in 2007 of the socalled quantum spin hall effect in hgte quantum wells, a new topological state of quantum matter. Why this paper is important importance of quantum spin hall effect. Gauge physics of spin hall effect pubmed central pmc. Straininduced quantum spin hall effect in twodimensional. Spintronics for next generation innovative devices wiley. This model is important because it provides a simple 2 band description of the quantum hall effect. Quantum hall effect 61 but this picture doesnt account for the ranges of b corresponding to the plateaux.
This is a course on the quantum hall effect, given in tifr, mumbai. Basic physics underlying the phenomenon is explained, along with diverse aspects such as the quantum hall effect as the resistance standard. However, the small band gap in materials that have been identified as qsh insulators limits. Pdf spin hall effects are a collection of relativistic spinorbit coupling phenomena in which electrical currents can. Spin polarization of the quantum spin hall edge states.
Experiments on topological insulator and quantum anomalous hall effect part i duration. It also provides a stepping stone to the 2d quantum spin hall insulator. The dimensionality of the zeeman interaction plays an important role in the qshe, and profoundly modifies. The conventional quantum hall effect is a particular example of the general relation if one views the electric field as a rate of change of the vector potential. The quantum spin hall effect is a fundamental property of. Spin hall effect she 1,2,3,4,5 refers generally to the transverse separation of the electron carriers of opposite spin, quantized along the axisz, which results in a net accumulation of spin but not charge on the left and right lateral edges of a nanoscale device. Pdf quantum renormalization of the spin hall effect t. Topologically distinct from all other known states of matter, including qh states, qsh states have been theoretically predicted and experimentally observed in mercury telluride quantum wells, 2,3 2.
In a twodimensional system the quantum spin hall effect qshe state is. Despite numerous theoretical predictions of a qshi state in a large number of thin films and 2d materials 59, its inherent characteristica quantum spin hall effect with its universal quantized conductancehas been experimentally established by a direct transport measurement only in inverted hgte quantum wells qws and brokengap inas. Evidence for a quantum spin hall phase in graphene decorated. The integer and fractional quantum hall effects were the first topological states to be discovered in the. Recently, this novel effect has been predicted and observed in hgte quantum wells. Quantum spin hall effect and their topological design of devices. The quantum spin hall state of matter is the cousin of the integer quantum hall state, and that does not require the application of a large magnetic. The quantum spin hall state is a state of matter proposed to exist in special, twodimensional, semiconductors that have a quantized spin hall conductance and a vanishing charge hall conductance. Jun 26, 2017 a quantum spin hall qsh insulator is a novel twodimensional quantum state of matter that features quantized hall conductance in the absence of a magnetic field, resulting from topologically. Spin hall effect, 2d topological insulator duration. The quantum spin hall effect is a unique phase of matter in which the bulk of the material is an insulator, but topological quantum.
Recently, a new class of topological states has emerged, called quantum spin hall qsh states or topological insulators see physics today, january 2008, page 19. Feb 14, 2020 at charge neutrality, the ensuing ground state is a quantum hall ferromagnet with two filled states of identical spin polarization and an edge dispersion that exhibits two counterpropagating, spinfiltered helical edge channels fig. It is unusual for a puretheory physics paper to make it into the journal science. Mele department of physics and astronomy, university of pennsylvania, philadelphia, pennsylvania 19104, usa received 22 june 2005. Stanford university with andrei bernevig, taylor hughes. The quantum spin hall effect qshe is observable in twodimensional metals without spin orbit coupling. The quantum spin hall effect for electrons allows for the existence of an unusual type of materialcalled a topological insulatorwhich conducts electricity on the surface but not through the.
The quantum spin hall effect is a fundamental property of light. Perspective is also given for recent advances in the quantum hall effect in oxides, narrowgap semiconductors and graphene, as well as a spinoff in physics to anomalous hall effect and spin hall effect. Theory and experiment markus konig1, hartmut buhmann1, laurens w. Quantum hall effect 55 skipping cyclotron orbits fourterminal sample configuration to measure the hall and longitudinal resistivities quantum hall effect 56 for a given plateau not a perfect conductor. The quantum spin hall qsh state is a topologically nontrivial state of quantum matter which preserves timereversal symmetry. This is the starting point for the definition of the z2 invariant 22, 23, 3740. This paper fills the missing piece giving a real world. Here, we predict existence of quantum spin hall effects and tunable spin transport in asgraphane, based on firstprinciple density functional theory and tight binding calculations. Quantum spin hall insulator state in hgte quantum wells. From the dirac equation of an electron in an anisotropic conduction band, the anisotropy of its motion dramatically affects its interaction with applied electric and magnetic fields. Beyond the potential technological applications, the intrinsic spin hall e. Quantum hall effect jung joo eun, kin min young youtube. Tunable spin transport in nanodevices is highly desirable to spintronics. Dynamical quantum hall effect in the parameter space pnas.
Quantum anomalous hallquantum spin hall effect in optical. Pdf we show that freespace light has intrinsic quantum spinhall effect qshe properties. A quantum spin hall qsh insulator is a novel twodimensional quantum state of matter that features quantized hall conductance in the absence of a. When the thickness of the quantum well is varied, the electronic state changes from a normal to an inverted type at a critical thickness d c. Quantum spin hall effect the qsh state can be thought of as b eff two copies of qh states, one for each spin component, each seeing the opposite magnetic field. Quantum spin hall state in monolayer 1twte 2 nature. Despite theoretical predictions of quantum spin hall effect qsh insulator via chemical functionalization, it is quite challenging to obtain a highquality sample, in which the toxicity is also an important factor that cannot be ignored.
This novel electronic state with timereversal invariance is gapped in the bulk and conducts charge and spin in gapless edge states. We fabricated such sample structures with low density and high mobility in which we could tune, through an external gate voltage, the carrier conduction from ntype to ptype, passing through an. Plotting the hall resistance essentially the reciprocal of the hall conductance of a lowtemperature twodimensional electron gas against the strength of the imposed magnetic field normal to the gas plane, one finds a stairlike quantized sequence of hall conductances very precisely equal to ne 2 h, where n is the integer that characterizes each. Variations of the free energy from 2000 to 5000 fs. The quantum spin hall effect goteborgs universitet. We experimentally and theoretically study artificially enhanced spin orbit coupling in graphene via. Apr 24, 2012 these results can be interpreted as a dynamical quantum hall effect in a parameter space. Request pdf quantum spin hall effect the quantum hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Andrei bernevig and shoucheng zhang department of physics, stanford university, stanford, california 94305, usa received 18 april 2005. It also provides a stepping stone to the 2d quantum spin hall.
Quantum hall effect article about quantum hall effect by. Quantum spin hall effect in iv vi topological crystalline insulators duration. Here, we report a class of quantum hall effect, the quantum parity hall qph effect, in which boundary channels are distinguished by even or. As a result, any interface between free space and a medium supporting. The quantum spin hall phase shares many similarities with the quantum hall effect. Graphenes exceptionally weak spin orbit couplingstemming from carbons low massposes the primary obstacle. Evidence for a quantum spin hall phase in graphene. The quantum spin hall effect and topological insulators xiaoliang qi is a research associate at the stanford institute for materials and energy science and shoucheng zhang is a professor of physics at stanford university in stanford, california. In order experiment was introduced a topological z 2, invariant who characterizes a state as trivial or nontrivial band insulator regardless if the state.
What the previously proposed real world examples are. We illustrate our findings by analyzing the response of interacting spin chains to a rotating magnetic field. Existence of the quantum hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. Z2 topological order and the quantum spin hall effect. Quantum spin hall effect and topological phase transition in. Concepts like the spin hall effect she69 and birefringent electron optics10 are explored with promising results. The unexpected discovery of the quantum hall effect was the result of basic research on silicon field effect transistors combined with my experience in metrology, the science of measurements.
Quantum spin hall insulator with a large bandgap, dirac. Bernevig and zhang, prl, 2006 the qsh state does not break the time reversal symmetry, and can exist without any external magnetic field. A quantum spin hall qsh insulator is a novel twodimensional quantum state of matter that features quantized hall conductance in the absence of a magnetic field, resulting from topologically. Disorder in the 2d system structural defects at heterojunction. The quantum hall effects remains one of the most important subjects to have emerged in condensed matter physics over the past 20 years. Quantum spin hall effect in twodimensional transition metal dichalcogenides xiaofeng qian,1 junwei liu,2 liang fu,2 ju li1 quantum spin hall qsh effect materials feature edge states that are topologically protected from backscattering. This quantum hall effect is referred to as the quantum anomalous hall qah effect. Effect of amidogen functionalization on quantum spin hall.
Hughes,1 shoucheng zhang1 we show that the quantum spin hall qsh effect, a state of matter with topological properties distinct from those of conventional insulators, can be realized in mercury telluridecadmium. We show that the quantum spin hall qsh effect, a state of matter with topological properties distinct from those of conventional insulators, can be realized in mercury telluridecadmium telluride semiconductor quantum wells. Knowledge about chemical functionalization is of fundamental importance to design novel twodimensional topological insulators. There have been many studies of the numerous possible mechanisms that could have given rise to she, but the gauge theory. We find that in an experimentally accessible low temperature regime the symmetry allowed spin orbit potential converts graphene from an ideal two dimensional semimetallic state to a quantum spin hall insulator. Pdf quantum spin hall effect and topological insulators for light. Surface transport and quantum hall effect in ambipolar black. Why those proposed real world examples are unrealistic importance of this paper. Two prominent ones are prange and girvin, the quantum hall e. The integer and fractional quantum hall effects were the first topological states to. Quantum hall effect an overview sciencedirect topics. Another effect, which demonstrates spin polarized charge transport, is the quantum hall effect.
Helical quantum hall phase in graphene on srtio3 science. Quantum spin hall effect and topological phase transition in hgte quantum wells b. Quantum spin hall effect spin orbit induced energy gap in graphene. The quantum spin hall effect is a unique phase of matter in which the bulk of the material is an insulator, but topological quantum states exist at the. Quantum spin hall effect and topological phase transition. Introduction to integer quantum hall effect by ganpathy murthy. After graduating from kyoto university in 1964, he was affiliated with the broadcasting science research laboratories of nhk japan broadcasting corporation until 1984.
Recent theory predicted that the quantum spin hall effect, a fundamentally new quantum state of matter that exists at zero external magnetic field, may be realized in hgtehg,cdte quantum wells. The quantum spin hall effect theory and experiment pdf. Based on this mechanism, we can explain why the gigantic spin hall effect in au with fe impurities was observed in recent experiments, while it is not visible in the anomalous. The search for topologically nontrivial states of matter has become an important goal for condensed matter physics. The fractional quantum hall effect, in particular, has opened up a new paradigm in the study of strongly correlated electrons, and it has been shown that new concepts, such as fractional statistics, anyon, chiral luttinger liquid and composite particles, are. Graphenes exceptionally weak spinorbit couplingstemming from carbons low massposes the primary obstacle.
Quantum spin hall state in monolayer 1twte 2 nature physics. Electrons and holes are trapped laterally by those potentials but are free in the other two dimensions. Quantum spin hall effect in silicene and twodimensional. We study the effects of spin orbit interactions on the low energy electronic structure of a single plane of graphene. 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 first four chapters require only basic quantum mechanics.
Another definition of a fractional topological insulator 20, 8890 is more. Monolayer asgraphane is constituted by using as adsorbing on graphane with honeycomb h vacancies. There are surprisingly few dedicated books on the quantum hall e. The quantum spin hall qsh phase is a time reversal invariant electronic state with a bulk electronic band gap that supports the transport of charge and spin in gapless edge states.
A new 2d electronic phase gapless edge states and transport time reversal symmetry and z 2 topological stability. We further connect the spin current generating spin hall effect to the inverse spin galvanic effect, which often accompanies the she, in which an electrical current induces a nonequilibrium spin. The quantum spin hall effect theory and experiment pdf download. Quantum spin hall effect in twodimensional transition.
In the seminal 2dimensional example of the quantum spin hall effect 51, it is related to the existence of spin oriented edge currents, such that each spin component has nonzero conductance. Quantum spin hall effect and topological phase transition in hgte quantum wells. Straininduced quantum spin hall effect in twodimensional methylfunctionalized silicene sich3 cengceng ren, weixiao ji, shufeng zhang, changwen zhang, ping li and peiji wang. Quantum anomalous hall quantum spin hall effect in optical superlattices ce shang,1,2,4 xianfeng chen,1,2 weidong luo,3 and fangwei ye1,2, 1the state key laboratory of advanced optical communication systems and networks, school of physics and astronomy, shanghai jiao tong university, shanghai 200240, china 2key laboratory for laser plasma, collaborative innovation center.
Quantum confinement of atoms and electrons to two dimensions 2d profoundly alters their electronic properties, giving rise to celebrated phenomena, such as the integer and fractional quantum hall qh effect, quantum spin hall effects 24, and interfacial superconductivity and magnetism, as well as technological development, such as. 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 experimentally and theoretically study artificially enhanced spinorbit coupling in graphene via random. Three dimensional generalization topological insulator, surface states. Quantum spin hall effect and tunable spin transport in as. The quantum spin hall effect and topological insulators. Jun 25, 2015 the quantum spin hall effect for electrons allows for the existence of an unusual type of materialcalled a topological insulatorwhich conducts electricity on the surface but not through the.
Quantum parity hall effect in bernalstacked trilayer. Provides new physics and new devices previously published work. The quantum hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Pdf quantum spin hall effect in electric and magnetic.