Threedimensional analogue of the dirac state in graphene has. Together with a detailed introduction by the editor, this volume serves as a stimulating and valuable reference for students and research workers in condensed matter physics and for those with a particle physics background. In the present paper we summarize the topological approach to fractional quantum hall effect fqhe via introduction of so called cyclotron braid subgroups which help us in understanding of the laughlin correlations specific for fqhe 14. Quantum spin hall effect and tunable spin transport in asgraphane l. The quantum spin hall state is a state of matter proposed to exist in special, twodimensional, semiconductors that have a quantized spinhall conductance and a vanishing chargehall conductance. Bernevig and zhang, prl, 2006 the qsh state does not break the time reversal symmetry, and can exist without any external magnetic field. Quantum spin hall effect and tunable spin transport in as. This paper fills the missing piece giving a real world. By varying the thickness of the quantum well, the band structure changes from a normal to an inverted. 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. Ppt quantum hall effects an introduction powerpoint. Quantum spin hall effect in two dimensional transition. Crp2s6 room temperature quantum anomalous hall effect in. Experimental realization of qsh figure from science 318, 766 2007.
The quantum spin hall effect and topological insulators. Enhanced spin hall effect by resonant skew scattering in orbitaldependent kondo effect. All of them have their genesis in the quantum hall e. Why this paper is important importance of quantum spin hall effect. Spin polarization of fractional quantum hall states with. Institute of fundamental and frontier sciences, university of electronic science and technology of china, chengdu 610054, china department of materials science and engineering, university. Crp2s6 room temperature quantum anomalous hall effect. Yet, there are strong anomalies seen in other properties, such as the surface acoustic wave velocity. Graphene and the quantum spin hall effect penn physics. It is unusual for a puretheory physics paper to make it into the journal science. This book is a compilation of major reprint articles on one of the most intriguing phenomena in modern physics. Physics the quantum hall effect gets more practical. The first proposal for the existence of a quantum spin hall state was developed by charles kane and gene mele who adapted an earlier model for graphene by f.
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 edges. 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 field. Spielman joint quantum institute, national institute of standards and technology and department of physics, university of maryland, gaithersburg, md 20899, usa introduction to spin hall effect w. 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 edges carrying up spins and down spins. Oct 19, 2017 the spin hall effect is a transport phenomenon consisting of the appearance of spin accumulation on the lateral surfaces of a sample carrying electric current. This causes a gap to open between energy bands, and electrons in the. To study this phenomenon, scientists apply a large magnetic field to a 2d sheet semiconductor. The quantum spin hall effect goteborgs universitet.
The main ingredient is the existence of spin orbit coupling, which can be understood as a momentumdependent magnetic field coupling to the spin of the electron. It is also called twodimensional topological insulator. 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. The spin hall effect, whereby flowing particles experience orthogonally directed, spin dependent lorentzlike forces, is observed in a quantum degenerate gas and used to produce a coldatom spin. Quantum hall effects an introduction 1 quantum hall effects an introduction m. The fractional quantum hall effect is caused by the coulomb interaction because the 2d electron system without the coulomb interaction yields no energy gap at the fractional filling factor. Room temperature quantum anomalous hall effect in singlelayer crp2s6 pei zhao, yandong ma, hao wang, baibiao huang and ying dai school of physics, state key laboratory of crystal materials, shandong university, shandanan str. Pdf quantum spin hall effect george rajna academia. The integer and fractional quantum hall effects were the first topo. Aug 19, 2015 controlling the spin of electrons within a device can produce surprising and substantial changes in its properties. Left the quantum hall effect qhe occurs in a twodimensional electron system under a large applied magnetic field. Quantum spin hall qsh effect materials feature edge states that are topologically protected from backscattering.
It is a simple consequence of the motion of charged particles in a magnetic eld. Quantum hall effect and topological insulators joint. Quantum spin hall effect has been proposed to have a separation of spin currents as an analogue of the charge currents separation in quantum hall effect, leading us to the era of topological insulators. 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. Such a spin hall insulator would be of intrinsic interest, since it would allow for spin currents to be generated without dissipation.
The discovery of quantum hall effect has motivated the use of topology instead of broken symmetry to classify the states of matter. A quantum spin hall system possesses a pair of helical edge states, in which an electric current can induce a transverse spin current or a spin accumulation near the system boundary. Quantum spin hall effect in a twoorbital model on a honeycomb lattice. Supporting information quantum spin hall effect and tunable spin transport in asgraphane l. Underlying all of these phenomena is an impressive theoretical edi. We use firstprinciples calculations to predict a class of largegap qsh. Levitov department of physics, massachusetts institute of technology, 77 massachusetts ave, cambridge, ma 029 electron edge states in graphene in the quantum hall e. What the previously proposed real world examples are. Lu,3 and feng liu 5, 1institute of fundamental and frontier sciences, university of electronic science and technology of china, chengdu 610054, china. The original, classical hall e ect was discovered in 1879 by edwin hall. References home university of waterloo university of. 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.
The essence of the quantum spin hall effect in real materials can be captured in explicit models that are particularly simple to solve. The spin hall effect has been observed in gaas 3,4. Hall effect first three figures are from wikipedia. In most cases the current carrying conductor will be a wire, upon the surface of which the spins will wind around the surface. Quantum spin hall effect and topological phase transition. Provides new physics and new devices previously published work. Spin hall effect quantum hall effect quantum spin hall effect part of members of the hall effect family. The kane and mele model is two copies of the haldane model such that the spin up electron exhibits a chiral integer quantum. View the table of contents for this issue, or go to the journal homepage for more.
The spin hall effect results in the aggration of spin the spin directions at one edge of a current carrying conducting material being opposite to the other edge. Quantum spin hall effect figure from science 301, 48 2003 the number of edge channels in the sample is directly related to the value of the quantum hall conductance figure from physics today feb 2010. The spin hall effect, whereby flowing particles experience orthogonally directed, spindependent lorentzlike forces, is observed in a quantumdegenerate gas and used to. Our work on the quantum spin hall qsh effect is motivated both by the quest. However, the small band gap in materials that have been identified as qsh insulators limits applications. Right the quantum anomalous hall effect has quantum hall features without an applied field. Electronic properties of novel topological quantum. This is the starting point for the definition of the z2 invariant 22, 23, 3740. The spin hall effect is a transport phenomenon consisting of the appearance of spin accumulation on the lateral surfaces of a sample carrying electric current. The quantum spin hall phase shares many similarities with the quantum hall effect. The qsh state can be thought of as two copies of qh states, one for each spin component, each seeing the opposite magnetic. Quantum spin hall effect is a spin version of quantum hall effect.
Drawing from many cutting edge fields, including physics, materials science, and electronics device technology, spintronics has provided the key concepts for many next generation information processing and transmitting technologies. The quantum hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Quantum spin hall effect and their topological design of devices. Why those proposed real world examples are unrealistic importance of this paper. Pdf simple notes on hall effect nishad tn academia. Theory and experiment the search for topologically nontrivial states of matter has become an important goal for condensed matter physics. Quantum spin hall effect and their topological design of. Lu, 3 and feng liu 5, 1 institute of fundamental and frontier sciences, university of electronic science and technology of china, chengdu 610054, china. Lu,3 and feng liu 5, 1institute of fundamental and frontier sciences, university of electronic science and technology of china, chengdu 610054, china 2 department of materials science and. In two dimensions the helical edge states give rise to the quantum spin hall qsh effect, in the absence of any external magnetic field.
The existence of the quantum hall effect requires breaking of the. Graphene quantum hall effect in high magnetic fields as the magnetic field grows, the ll spectrum assumed in eq. 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. Spatial separation is at the heart of both the quantum hall qh and the quantum spin hall qsh effects. Quantum anomalous hall effect and quantum spin hall effect. Spintronics for next generation innovative devices wiley. Another definition of a fractional topological insulator 20, 8890 is more analogous to the. So there is still something very strange occurring. Homotopy approach to fractional quantum hall effect. The curve of polarization versus magnetic field has wide plateaus. Controlling the spin of electrons within a device can produce surprising and substantial changes in its properties.
In the sh effect, a transverse spin current flows, say, in the x direction, in response to an applied electric field in the y direction. Pdf spin hall effects are a collection of relativistic spinorbit coupling phenomena in which electrical. Phenomenology of the quantum spin hall effect one key element that was instrumental in arriving at the theoretical prediction of the qsh state is the prediction of the intrinsic spin hall sh effect in doped semiconductors 15, 16. The quantum hall effect is an example of a phenomenon having topological features that can be observed in certain materials under harsh and stringent laboratory conditions large magnetic field, near absolute zero temperature. In order experiment was introduced a topological z 2, invariant who characterizes a state as trivial or nontrivial band insulator regardless if the state. In quantum spin liquids, this dynamical disorder is quantum mechanical in origin. This will provide a useful background for our discussion of the quantum hall e ect. 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. Hughes, chaoxing liu, xiaoliang qi, shoucheng zhang download pdf. Quantum spin liquids are currently where some of the most active theoretical and experimental work on quantum materials is going on, blundell says. Electronic properties of novel topological quantum materials. The sh effect can be thought of as the spin counterpart to the classical charge hall effect. The twodimensional topological insulator mercury telluride can be described by an effective hamiltonian that is essentially a taylor expansion in the wave vector k of the interactions between the lowest. Haldane which exhibits an integer quantum hall effect.
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