Experimental observation of the spinhall effect in a twodimensional spinorbit coupled semiconductor system j. We theoretically propose that the spin hall effect occurs in ptype semiconductors even without an aid of impurity scattering. 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. The sh effect can be thought of as the spin counterpart to the classical charge hall effect. 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. Here, the authors experimentally disentangle the spinhall effect and inverse spingalvanic. Andrei bernevig and shoucheng zhang department of physics, stanford university, stanford, california 94305, usa received 18 april 2005.
We show that the experimental result is quantitatively consistent with the. Basic elements of spintronics spin electronics spin currents. Ferroelectric rashba semiconductors fersc have recently emerged as a promising class of spintronics materials. Ultrafast optical imaging of the spin hall effect of light. Contrast this with resistivity, which has units of m. 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. 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. Intrinsic spin hall effect in semiconductors and metals. Pdf generating spin currents in semiconductors with the. Spin torque ferromagnetic resonance induced by the spin hall effect luqiao liu, takahiro moriyama, d. 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. At the edges of a sample, the spin current results in accumulation of spins, similar to charge accumulation in the conventional hall effect. The flow of electrons is in the opposite direction to the conventional current.
We will study the hall effect in a parallelepipedic semiconductor sample of sizes a, b, c see figure 1. Complementary spinhall and inverse spingalvanic effect. Giant intrinsic spin hall effect in w3ta and other a15. Giant spin pumping and inverse spin hall effect in the.
Experimental discovery of the spinhall effect in rashba. Motivations in this work, we study intrinsic spin hall effect in semiconductors and metals by. W3ta, ta3sb, and cr3ir having spin hall conductivities. With this criterion, we predict that some band insulators have nonzero spin hall effect. Observation of the spin hall effect in semiconductors. Thus electrons accumulate along the side ag of the metal, which will make ag negatively charged and lower its potential. The polarization is outofplane and has opposite sign for the two. 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. Pdf observation of the spin hall effect in semiconductors. Theory of spin hall effects in semiconductors wiley online library.
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. The quantum spin hall qsh state is a topologically nontrivial state of quantum matter which preserves timereversal symmetry. The spin hall effect is a phenomenon of inducing spin current by an external electric field. 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. 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. To explain the hall effect, consider a slab of metal carrying a current. Schematic illustration of the spin hall effect of light. The quantum spin hall effect and topological insulators. 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. Exciton hall effect semiconductor semiconductors spin spin hall effect basics dynamics electronics. Ntype semiconductors have a large number of donors, dopant atoms that donate electrons to the conduction band. Awschalom electrically induced electron spin polarization near the edges of a semiconductor channel was detected and imaged with the use of kerr rotation microscopy.
Pdf simple notes on hall effect nishad tn academia. The spin hall effect is a relativistic spinorbit coupling phenomenon, which can be used to electrically generate or detect spin currents in nonmagnetic systems. 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. 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. This intrinsic effect is due to the berry phase in momentum space, representing topological structure of the bloch. 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.
We also discuss a criterion for nonzero spin hall effect. When a linearly polarized beam propagating in the xz plane is incident at an optical interface at a nonnormal incident angle its circular. We recently proposed that this effect can occur in ptype semiconductors without relying upon any disorder scattering s. Strain dependence of spin hall effect in ntype wurtzite semiconductors v. 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.
It is most easily detected when the magnetic material is an insulator which eliminates. 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. This voltage is a direct measure of the magnetic field as long as the current is constant. Experimental discovery of the spinhall effect in rashba spinorbit coupled semiconductor systems j. Pdf spin hall effects are a collection of relativistic spinorbit coupling phenomena in which. Here, we predict and explain the large intrinsic she in. Here, we use spin pumping and the inverse spin hall effect to demonstrate successful spin injection at room temperature from a metallic ferromagnet.
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 origin of the spinhall effect in metals is still under debate 5355. The polarization is outofplane and has opposite sign for the two edges, consistent with the predictions of the spin hall effect. 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. Experimental observation of the spinhall effect in a two. The essence of the quantum spin hall effect in real materials can be captured in explicit models that are particularly simple to solve. 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.
Electrically induced electronspin polarization near the edges of a semiconductor channel was detected and imaged with the use of kerr rotation microscopy. 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. A hall of spinthe experimental observation of the spin hall effect. 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. Spin hall effect in prototype rashba ferroelectrics gete. We describe an intrinsic spinhall effect she in ntype bulk zincblende semiconductors with a topological origin. Inverse spin hall effect from pulsed spin current in. The berry curvature of this gauge field and the corresponding. Observation of the spin hall effect in semiconductors y. The spin current is described by a tensor q ij, where the first index indicates the direction of flow, while the second one says which component of the spin is flowing. Observation of the spin hall effect in semiconductors et.
Two groups observe the spin hall effect in semiconductors. Hall effect in doped semiconductors and metals in the light of recent experiments on. Spinorbit torques could enable a new generation of lowpower electrically controlled memory devices. Awschalom electrically induced electronspin polarization near the edges of a semiconductor channel was detected and imaged with the use of kerr rotation microscopy. 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. Spin hall effect in semiconductors pritzker school of. This is then followed by a discussion on the topological insulators. Spin hall effect in ptype semiconductors realizing. The spin hall effect in strained and unstrained bulk gaas has been recently observed experimentally by kato et. Spins of opposite sign accumulate on opposite sides of a semiconductor in response to an external electric field. Hall coe cient is a parameter that measures the magnitude of the hall e ect in the sample. He was awarded the state prize of ussr in 1973 and the ioffe prize of the russian academy of sciences in 1993.
Ab initio calculation of the intrinsic spin hall effect in. A weak dependence on crystal orientation for the strained samples suggests that the mechanism is the extrinsic spin hall effect. Spintorque ferromagnetic resonance induced by the spin. Spin and orbitalangularmomentum hall effects in ptype zincblende semiconductors iv. Subsequently, the qsh state was independently proposed in graphene 11 and in strained semiconductors 12. 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.
Such an experiment was recently done by miah14 with gaas illuminated by circularly. 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. These kinds of sensors with typical dimensions of the sensitive element of 0. 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. 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. 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. Quantum spin hall effect in inverted type ii semiconductors. It introduces a basic framework and discusses the mechanism of the she in semiconductors and in metals. 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. Spinhall effect of collimated electrons in zincblende.
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