Subsequently, the qsh state was independently proposed in graphene 11 and in strained semiconductors 12. The essence of the quantum spin hall effect in real materials can be captured in explicit models that are particularly simple to solve. Thus electrons accumulate along the side ag of the metal, which will make ag negatively charged and lower its potential. Pdf simple notes on hall effect nishad tn academia. Ab initio calculation of the intrinsic spin hall effect in. Intrinsic spin hall effect in semiconductors and metals. Here, we predict and explain the large intrinsic she in. Ntype semiconductors have a large number of donors, dopant atoms that donate electrons to the conduction band. Anomalous hall effect in ferromagnetic semiconductors.
The peculiar coupling between spin and polar degrees of freedom responsible for several exceptional properties, including ferroelectric switching of rashba spin texture, suggests that the electrons spin could be. Measurements of unstrained gallium arsenide and strained indium gallium arsenide. Since the electrons have an internal degree of freedom, spin, they are characterized not only by charge density and electric current, but also by spin density and spin current. We will study the hall effect in a parallelepipedic semiconductor sample of sizes a, b, c see figure 1. Electrically induced electronspin polarization near the edges of a semiconductor channel was detected and imaged with the use of kerr rotation microscopy. Pdf observation of the spin hall effect in semiconductors. He was awarded the state prize of ussr in 1973 and the ioffe prize of the russian academy of sciences in 1993. Experimental observation of the spinhall effect in a two. Such an experiment was recently done by miah14 with gaas illuminated by circularly. Spin torque ferromagnetic resonance induced by the spin hall effect luqiao liu, takahiro moriyama, d. Strain dependence of spin hall effect in ntype wurtzite semiconductors v. The spin hall effect she is the conversion of charge current to spin current, and nonmagnetic metals with large shes are extremely sought after for spintronic applications, but their rarity has stifled widespread use.
Pdf spin hall effects are a collection of relativistic spinorbit coupling phenomena in which. We describe an intrinsic spinhall effect she in ntype bulk zincblende semiconductors with a topological origin. This intrinsic effect is due to the berry phase in momentum space, representing topological structure of the bloch. Experimental observation of the spinhall effect in a twodimensional spinorbit coupled semiconductor system j. We also discuss a criterion for nonzero spin hall effect. Observation of the spin hall effect in semiconductors. Threedimensional 3d topological insulators are known for their strong spinorbit coupling soc and the existence of spintextured surface states that might be potentially exploited for topological spintronics. Spin hall effect in ptype semiconductors realizing. Two groups observe the spin hall effect in semiconductors.
Spin hall effect in prototype rashba ferroelectrics gete. The flow of electrons is in the opposite direction to the conventional current. Buhrman cornell university, ithaca, new york, 14853 received 12 october 2010. In addition to the spin hall effect, magnets may exhibit a magnetic spin hall effect mshe, as was recently discovered m. Experimental discovery of the spinhall effect in rashba. Pdf generating spin currents in semiconductors with the. Awschalom electrically induced electron spin polarization near the edges of a semiconductor channel was detected and imaged with the use of kerr rotation microscopy.
Observation of the spin hall effect in semiconductors y. Hall coe cient is a parameter that measures the magnitude of the hall e ect in the sample. 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. Spin and orbitalangularmomentum hall effects in ptype zincblende semiconductors iv. In the following, we interpret g helical to occur in the topological side surfaces of the bts platelets as a consequence of a spincurrent caused by the bulk spinhall effect 3032 33 34. Furthermore, it is found that the spin hall effect can be strongly manipulated by strains, and that the ac spin hall conductivity is large in pure as well as doped semiconductors. Here, the authors experimentally disentangle the spinhall effect and inverse spingalvanic. The berry curvature of this gauge field and the corresponding. 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.
The quantum spin hall effect and topological insulators. At the edges of a sample, the spin current results in accumulation of spins, similar to charge accumulation in the conventional hall effect. F so j f so j s more spin up electrons are deflected to the right than to the left and viceversa for spin down for a given deflection, spin up and spin down electrons make a side. Inverse spin hall effect from pulsed spin current in.
This is then followed by a discussion on the topological insulators. A pure spin current is a flow of spin angular momentum without any charge current, which can be realized, for example, by spinup and spindown electrons moving in opposite directions. Hall effect in doped semiconductors and metals in the light of recent experiments on. In the simplest version of a spin hall effect, an electrical current passes through a sample with spinorbit interaction, and induces a spin polarization near the. It is most easily detected when the magnetic material is an insulator which eliminates. Spin hall magnetoresistance smr is a transport phenomenon that is found in some electrical conductors that have at least one surface in direct contact with another magnetic material due to changes in the spin current that are present in metals and semiconductors with a large spin hall angle.
Observation of the spin hall effect in semiconductors et. To explain the hall effect, consider a slab of metal carrying a current. The origin of the spinhall effect in metals is still under debate 5355. In a similar setup but using the inverse spinhall effect alone 50, the spin polarization was converted to an electrical signal and at least an order of magnitude weaker electrical signal was detected in metals, such as al 51, 52. In particular, the spin hall effect could allow spintronic devices to be manufac tured with the same techniques that are currently used to make semiconductor. These kinds of sensors with typical dimensions of the sensitive element of 0. Ferroelectric rashba semiconductors fersc have recently emerged as a promising class of spintronics materials. Spins of opposite sign accumulate on opposite sides of a semiconductor in response to an external electric field.
Two groups observe the spin hall effect in semiconductors in 1971, mikhail dyakonov and vladimir perel of the ioffe institute in leningrad proposed a new transport phenomenon. Hall effect sensors are based on a thin film of semiconducting material typically indium arsenide in which a voltage perpendicular to an applied current and an applied magnetic field appears fig. A weak dependence on crystal orientation for the strained samples suggests that the mechanism is the extrinsic spin hall effect. Schematic illustration of the spin hall effect of light. Spin hall effect in semiconductors pritzker school of. Contrast this with resistivity, which has units of m. Giant intrinsic spin hall effect in w3ta and other a15. This effect consists in the appearance of an electric field called hall field eh r, due to the deviation of the charge carrier trajectories by an external magnetic field.
This book describes beautiful optical and transport phenomena related to the electron and nuclear spins in semiconductors with emphasis on a clear presentation of the physics involved. Quantum spin hall effect in inverted type ii semiconductors. Awschalom electrically induced electronspin polarization near the edges of a semiconductor channel was detected and imaged with the use of kerr rotation microscopy. In the framework of the dimmock model of the energy spectrum in ivvi narrowgap semiconductors like pbte, snte, and their alloys, we calculate the intrinsic contribution to spin hall conductivity. Significance of the hall effect on semiconductors gulpmatrix. 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. The spin hall effect is a phenomenon of inducing spin current by an external electric field. It introduces a basic framework and discusses the mechanism of the she in semiconductors and in metals. We show that the experimental result is quantitatively consistent with the. Theory of spin hall effects in semiconductors wiley online library. The inverse spin hall effect ishe 1, that is when a spin current induces a transverse charge current, is mathematically equivalent to the she due to onsager symmetry relations. When a collimated flux of electrons is injected into a zincblende semiconductor with dresselhaus spinorbit interaction, a nontrivial gauge structure appears in the momentum k space of the electrons. This voltage is a direct measure of the magnetic field as long as the current is constant.
We show that the bulk dresselhauss k3 spin orbit coupling term leads to an intrinsic spin hall effect in ndoped bulk gaas, but without the appearance of uniform magnetization. When a linearly polarized beam propagating in the xz plane is incident at an optical interface at a nonnormal incident angle its circular. The quantum spin hall qsh state is a topologically nontrivial state of quantum matter which preserves timereversal symmetry. Coherent spin precession in a rashba effective magnetic field in the channel of a spin field effect transistor and the spin hall effect are the two most compelling topics in this area. Giant spin pumping and inverse spin hall effect in the. This paper is the first to demonstrate the inverse spin hall effect in a range of organic semiconductors with unprecedented sensitivity, although a 20 study by other researchers demonstrated. If the metal is placed in a magnetic field b at right angles to the face agdc of the slab and directed from cd to ag. In the original proposal 2, 3 an impurity mechanism was suggested, where spin. Andrei bernevig and shoucheng zhang department of physics, stanford university, stanford, california 94305, usa received 18 april 2005. Exciton hall effect semiconductor semiconductors spin spin hall effect basics dynamics electronics. Experimental discovery of the spinhall effect in rashba spinorbit coupled semiconductor systems j. We recently proposed that this effect can occur in ptype semiconductors without relying upon any disorder scattering s. Spinorbit torques could enable a new generation of lowpower electrically controlled memory devices. A hall of spinthe experimental observation of the spin hall effect.
Perel he has predicted new spinrelated transport phenomena, one of which, now called the spin hall effect, has become a subject of extensive experimental and theoretical studies. Motivations in this work, we study intrinsic spin hall effect in semiconductors and metals by. Basic elements of spintronics spin electronics spin currents. Ultrafast optical imaging of the spin hall effect of light. The sh effect can be thought of as the spin counterpart to the classical charge hall effect. Spintorque ferromagnetic resonance induced by the spin. Spin current, spin accumulation and spin hall effect saburo takahashi and sadamichi maekawacreation and control of spin current in solids koki takanashielectricallygenerated pure spin current in graphene masashi shiraishithis content was downloaded from ip address 40. The spin hall effect in strained and unstrained bulk gaas has been recently observed experimentally by kato et. With this criterion, we predict that some band insulators have nonzero spin hall effect.
537 257 1157 894 167 1143 861 547 51 1329 605 896 500 1233 544 566 27 772 1094 1503 1286 704 785 976 1246 873 614 866 1097 557 975 218 537 730 609 601 1050 841 1359 1400 1399 899 331 331 1383 67 421 760 1122 1359