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. By analyzing fundamental spin properties of maxwell waves, we show that freespace light exhibits an intrinsic quantum spin hall effectsurface modes with strong spinmomentum locking. Measuring the inverse spin hall effect ishe using the ppmsdynacoolversalab 62518. Course on topology in condensed matter 10,804 views.
The quantum hall effect or integer quantum hall effect is a quantum mechanical version of the hall effect, observed in twodimensional electron systems subjected to low temperatures and strong magnetic fields, in which the hall conductance. Experimental signatures of the qsh effect have recently been reported in an atomically thin material, monolayer wte2. We show that spin splitting of the zeroth landau level g ives rise to counterpropagating modes with opposite spin polarization. A novel topological insulator with tunable edge states, called a quantum spin quantum anomalous hall qsqah insulator, is predicted in a heterostructure of a hydrogenated sbsb2h monolayer on. There occurs an analogous phenomenon, the quantum spin hall effect, where a spin current flows instead of a charge current. 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 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. 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. The quantum spin hall effect is a fundamental property of light. The quantum spin hall effect and topological insulators. 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. 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. These chiral spin modes le ad to a rich variety of spin current states, depending on the spin. Quantum spin hall effect spin orbit induced energy gap in graphene.
In the new study, researchers bring together one of physics most venerable set of equations those of james clerks. Pdf quantum renormalization of the spin hall effect. Concepts like the spin hall effect she69 and birefringent electron optics10 are explored with promising results. Quantum spin hall effect and topological phase transition. Graphene and the quantum spin hall effect astronomy. Petr kratochvilpublic domain in a paper that crystalizes knowledge from a. Quantum hall effects an introduction 1 quantum hall effects an introduction m. Graphene, the quantum spin hall effect and topological insulators i.
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. 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. Pdf quantum anomalous hall effect in real materials. Unconventional quantum hall effect in graphene zuanyi li department of physics, university of illinois at urbanachampaign, urbana 61801 abstract graphene is a new twodimensional material prepared successfully in experiments several years ago. Graphenes exceptionally weak spin orbit couplingstemming from carbons low massposes the primary obstacle. Quantum spin hall effect intro by charles kane youtube.
Quantum spin hall effect and topological phase transition in hgte quantum wells b. Ppt quantum hall effects an introduction powerpoint. These results can be interpreted as a dynamical quantum hall effect in a parameter space. 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.
Work supported in part by us department of energy contract deac0276sf00515. We predict that the qshe can be observed in an experimentally accessible low temperature regime in silicene with the spin orbit band gap of 1. Jan 14, 20 steven girvin quantum hall effect institute for quantum computing. Quantum spin hall effect in twodimensional transition. A twodimensional 2d topological insulator exhibits the quantum spin hall qsh effect, in which topologically protected conducting channels exist at the sample edges. A0 2 quantum design an important first step before measuring the ishe response, is to first map out the conventional fmr spectra as the ishe voltage should closely follow the fmr. Pdf quantum spin hall effect in electric and magnetic. The quantum spin hall effect and its importance youtube.
Basic physics underlying the phenomenon is explained, along with diverse aspects such as the quantum hall effect as the resistance standard. Existence of the quantum hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. Understanding has required concepts and mathematical techniques from all corners of theoretical physics, including some completely new ideas. Evidence for a quantum spin hall phase in graphene. 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.
The quantum anomalous hall qah effect68, a zero magnetic field manifestation of the integer quantum hall effect, originates from the exchange interaction between electron spin and magnetism and exhibits quantized hall resistance and zero longitudinal resistance. View the table of contents for this issue, or go to the journal homepage for more. Pdf under a strong magnetic field, the quantum hall qh effect can be observed in twodimensional electronic gas systems. The quantum hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. The existence of the quantum hall effect requires breaking of the time reversal symmetry caused by an external magnetic. 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.
We use firstprinciples calculations to predict a class of largegap qsh insulators in twodimensional transition metal dichalcogenides with 1t. In this work, we predict a quantized spin hall effect in the absence of any magnetic field, where the intrinsic spin hall conductance is quantized. This will provide a useful background for our discussion of the quantum hall e. We experimentally and theoretically study artificially enhanced spin orbit coupling in graphene via. Pdf the original motivation of great interest to topological insulators was the hope to observe the quantum spin hall effect. 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.
When electrons are confined in twodimensional materials, quantum mechanically enhanced transport phenomena such as the quantum hall effect can be observed. Right the quantum anomalous hall effect has quantum hall features without an applied 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. The quantum spin hall effect qshe is observable in twodimensional metals without spin orbit coupling. Experimental observation of the quantum hall effect and. Pdf quantum spin hall effect george rajna academia. 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. Z2 topological order and the quantum spin hall effect. It is a simple consequence of the motion of charged particles in a magnetic. 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. Although the spin hall effect was predicted over three decades ago, it received little attention until studies on the intrinsic nature of its ferromagnetic cousin, the anomalous hall effect an additional contribution to the hall resistivity in magnetic materials, led to the prediction of a similar large spin hall effect in strongly spin. Andrei bernevig and shoucheng zhang department of physics, stanford university, stanford, california 94305, usa received 18 april 2005. Introduction to the quantum hall effect and topological phases mark o. It was shown that hgtebased quantum well structures are the most suitable candidates for its experimental realization.
In two dimensions the helical edge states give rise to the quantum spin hall qsh effect, in the absence of any external magnetic field. This quantum hall effect is referred to as the quantum anomalous hall qah effect. Left the quantum hall effect qhe occurs in a twodimensional electron system under a large applied magnetic field. I think that what the authors are trying to do is emphasize the difference between the quantized spin hall effect and the quantum spin hall effect. The quantum spin hall effect and topological insulators xiaoliang qi and shoucheng zhang in topological insulators, spin orbit coupling and timereversal symmetry combine to form a novel state of matter predicted to have exotic physical properties.
Mele department of physics and astronomy, university of pennsylvania, philadelphia, pennsylvania 19104, usa received 22 june 2005. The quantum spin hall effect is a fundamental property of. Jun 26, 2015 the latter ones result in remarkable geometric and topological phenomena related to the spin1 massless nature of photons. In a twodimensional system the quantum spin hall effect qshe state is characterized by an insulating bulk and two counterpropagating. Here, we directly image the local conductivity of monolayer wte2 using microwave impedance microscopy. 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. 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. A quantum spin hall system possesses a pair of helical edge states. 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. Quantum anomalous hall effect in twodimensional magnetic.
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. In this work,we predict a quantized spin hall effect in the. Enhanced spin hall effect by resonant skew scattering in orbitaldependent kondo effect. The quantum spin hall effect goteborgs universitet. Quantum spin hall effect and topological phase transition in hgtequantum wells taylor l. Effect of amidogen functionalization on quantum spin hall. It exhibits the quantum spin hall effect, in which an electric current can induce a transverse spin current or spin accumulation near the system boundary. The qh effect without landau levels is referred to as the quantum anomalous hall effect. 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.
An atomic layer of tin in a buckled honeycomb lattice, termed stanene, is a promising largegap twodimensional topological insulator for realizing roomtemperature quantum spin hall effect and therefore has drawn tremendous interest in recent years. Knowledge about chemical functionalization is of fundamental importance to design novel twodimensional topological insulators. As i will describe shortly, quantized spin hall effect is not possible. Electron edge states in graphene in the quantum hall e. When electrons are confined in twodimensional materials, quantum mechanically enhanced transport phenomena such as the quantum hall effect.
Pdf quantum spin hall effect in 2d topological insulators. What conductance is measured for the quantum spin hall state. Theory and experiment markus konig1, hartmut buhmann1, laurens w. 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. Graphene, the quantum spin hall effect and topological insulators.
Quantum spin hall effect in a twoorbital model on a honeycomb lattice. The sh effect can be thought of as the spin counterpart to the classical charge hall effect. 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. 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 integer and fractional quantum hall effects were the first topological states to be.
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. It is unusual for a puretheory physics paper to make it into the journal science. The spin hall effect is a phenomenon in which, in the absence of a magnetic field, particles such as electrons experience a lorentzlike force with a direction depending on each particles spin. Quantum spin hall qsh effect materials feature edge states that are topologically protected from backscattering. The quantum spin hall effect is a fundamental property of light 25 june 2015 credit. The quantum spin hall effect theory and experiment pdf. Measuring the inverse spin hall effect ishe using the. We will see, below, that the quantum hall states integer or fractional are characterized by the property. In a twodimensional system the quantum spin hall effect qshe state is characterized by an insulating bulk and two counterpropagating helical edge states. For example, say you are trying to observe the spin analogue of the integer quantum hall effect. However, the small band gap in materials that have been identified as qsh insulators limits applications.
Quantum spin hall effect in iv vi topological crystalline insulators duration. In this video, laurens molenkamp outlines how his teams focus on. They are typical phenomena on the topological insulator. Stanford university with andrei bernevig, taylor hughes. Because the electronic structures of sn allotropes are sensitive to lattice strain, e. Another effect, which demonstrates spin polarized charge transport, is the quantum hall effect. In 1988, it was proposed that there was quantum hall effect without landau levels. This precise ordering of the electrons into spinseparated, perfectly conducting channels is known as the quantum spin hall effect, which is a classic example of a topological insulator a material that is an electrical insulator on the inside but that can conduct electricity on its surface. Bernevig and zhang, prl, 2006 the qsh state does not break the time reversal symmetry, and can exist without any external magnetic field. Pdf quantum spinquantum anomalous hall effect with. Pdf quantum renormalization of the spin hall effect t.
The fractional quantum hall effect fqhe is a collective behaviour in a twodimensional system of electrons. Quantum hall effect an overview sciencedirect topics. Dynamical quantum hall effect in the parameter space pnas. Quantum hall effects world scientific publishing company. Introduction to the quantum hall effect and topological phases.
In particular magnetic fields, the electron gas condenses into a remarkable liquid state, which is very delicate, requiring high quality material with a low carrier concentration, and extremely low temperatures. 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. The quantum spin hall effect theory and experiment pdf download. A new 2d electronic phase gapless edge states and transport time reversal symmetry and z 2 topological stability. This book is a compilation of major reprint articles on one of the most intriguing phenomena in modern physics. 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. 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. A relativistic version of the quantum spin hall effect was introduced in the 1990s for the numerical simulation of chiral gauge theories. The first four chapters require only basic quantum mechanics. This is a course on the quantum hall effect, given in tifr, mumbai. Quantum anomalous hallquantum spin hall effect in optical. Quantum spin hall effect and topological phase transition in.
Graphene and the quantum spin hall effect upenn physics. Quantum spin hall effect in silicene and twodimensional. 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. These edge channels are protected by time reversal symmetry and spin currents propagate without dissipation. Three dimensional generalization topological insulator, surface states. Recently, the theoretical prediction of the intrinsic spin hall e.
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