Quantum Interference Control of Ballistic Pure Spin Currents in Semiconductors

Stevens, Martin J.; Smirl, Arthur L.; Bhat, Ravi; Najmaie, Ali; Sipe, J. E.; Driel, Henry van

doi:10.1103/physrevlett.90.136603

Cited by 284 publications

(213 citation statements)

References 11 publications

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“…Since realization of the total pure spin currents has been detected experimentally in optical pump-probe experiments, 57 and several theoretical schemes are proposed to detect them indirectly via various electrical measurements, 7,30,58 we focus in this sec- tion on the properties of total spin Hall current I s trans (m y ) on different transverse cross sections of four-terminal devices, which is obtained from Eq. (49) by summing the bond spin currents.…”

Section: Total Spin Hall Current Vs Local Spin Hall Current: Lanmentioning

confidence: 99%

Imaging mesoscopic spin Hall flow: Spatial distribution of local spin currents and spin densities in and out of multiterminal spin-orbit coupled semiconductor nanostructures

2006

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We introduce the concept of bond spin current, which describes the spin transport between two sites of the lattice model of a multiterminal spin-orbit (SO) coupled semiconductor nanostructure, and express it in terms of the spin-dependent nonequilibrium (Landauer-Keldysh) Green functions of the device. This formalism is applied to obtain the spatial distribution of microscopic spin currents in clean phase-coherent two-dimensional electron gas with the Rashba-type of SO coupling attached to four external leads. Together with the corresponding profiles of the stationary spin density, such visualization of the phase-coherent spin flow allow us to resolve several key issues for the understanding of mechanisms which generate pure spin Hall currents in the transverse leads of ballistic devices due to the flow of unpolarized charge current through their longitudinal leads: (i) while bond spin currents are non-zero locally within the SO coupled region even in equilibrium (when all leads are at the same potential), the total spin current obtained by summing the bond spin currents over an arbitrary cross section is zero so that no spin can actually be transported by such equilibrium currents; (ii) when device is brought into nonequilibrium steady current state by external voltage difference applied between the longitudinal leads, only the wave functions (or Green functions) around the Fermi energy contribute to the total spin current through a given transverse cross section; (iii) the total spin Hall current is not conserved within the SO coupled region; however, it becomes conserved and physically well-defined quantity in the ideal leads where it is, furthermore, equal to the spin current obtained within the multiprobe Landauer-Büttiker scattering formalism. The local spin current profiles crucially depend on whether the sample is smaller or greater than the spin precession length, thereby demonstrating its essential role as the characteristic mesoscale for the spin Hall effect in ballistic multiterminal semiconductor nanostructures. Although static spin-independent disorder reduces the magnitude of the total spin current in the leads, the bond spin currents continue to flow through the whole diffusive 2DEG sample, without being localized as edge spin currents around any of its boundaries. Recent experimental observation of the spin Hall effect 1,2 opens new avenues for the understanding of fundamental role which spin-orbit (SO) couplings 3,4 can play in transport and equilibrium properties of semiconductor structures. While SO coupling effects are tiny relativistic corrections for particles moving through electric fields in vacuum, they can be enhanced in solids by several orders of magnitude due to the interplay of crystal symmetry and strong crystalline potential. 3,4 Furthermore, harnessing of spin currents induced by the spin Hall effect offers new possibilities for the envisioned all-electrical manipulation of spin for semiconductor spintronics applications 5 where electrical fields can access individual spins on s...

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Section: Total Spin Hall Current Vs Local Spin Hall Current: Lanmentioning

confidence: 99%

Imaging mesoscopic spin Hall flow: Spatial distribution of local spin currents and spin densities in and out of multiterminal spin-orbit coupled semiconductor nanostructures

2006

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“…(There are also novel ways to generate pure spin currents, without accompanying charge currents. [6][7][8][9][10] ) The concept of electrical spin injection was first proposed by Aronov,11 and experimentally confirmed by Johnson and Silsbee,12 who also formulated the problem from a nonequilibrium thermodynamics and drift-diffusion view. 13,14 An equivalent description in terms of quasichemical potentials, convenient to treat discrete (junction) systems, was formulated systematically by Rashba.…”

Section: Introductionmentioning

confidence: 99%

Theory of thermal spin-charge coupling in electronic systems

et al. 2012

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The interplay between spin transport and thermoelectricity offers several novel ways of generating, manipulating, and detecting nonequilibrium spin in a wide range of materials. Here, we formulate a phenomenological model in the spirit of the standard model of electrical spin injection to describe the electronic mechanism coupling charge, spin, and heat transport and employ the model to analyze several different geometries containing ferromagnetic (F) and nonmagnetic (N) regions: F, F/N, and F/N/F junctions, which are subject to thermal gradients. We present analytical formulas for the spin-accumulation and spin-current profiles in those junctions that are valid for both tunnel and transparent (as well as intermediate) contacts. For F/N junctions, we calculate the thermal spin-injection efficiency and the spin-accumulation-induced nonequilibrium thermopower. We find conditions for countering thermal spin effects in the N region with electrical spin injection. This compensating effect should be particularly useful for distinguishing electronic from other mechanisms of spin injection by thermal gradients. For F/N/F junctions, we analyze the differences in the nonequilibrium thermopower (and chemical potentials) for parallel and antiparallel orientations of the F magnetizations, as evidence and a quantitative measure of the spin accumulation in N. Furthermore, we study the Peltier and spin Peltier effects in F/N and F/N/F junctions and present analytical formulas for the heat evolution at the interfaces of isothermal junctions.

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“…spin accumulation) in nonmagnetic SC is a central issue of SC-based spintronics 1,[3][4][5] . Significant progress has been made on the spin accumulation in various SC systems by means of circularly polarized light 4,6 , spin-polarized tunneling [7][8][9][10][11][12][13] , hotelectron spin filtering 14,15 , spin-orbit interaction 16,17 , or magnetization dynamics 18,19 .…”

mentioning

confidence: 99%

Thermal Spin Injection and Accumulation in CoFe/MgO/n-type Ge Contacts

Jeon¹,

Min²,

Park³

et al. 2013

Extended Abstracts of the 2013 International Conference on Solid State Devices and Materials

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Understanding the interplay between spin and heat is a fundamental and intriguing subject. Here we report thermal spin injection and accumulation in CoFe/MgO/n-type Ge contacts with an asymmetry of tunnel spin polarization. Using local heating of electrodes by laser beam or electrical current, the thermally-induced spin accumulation is observed for both polarities of the temperature gradient across the tunnel contact. We observe that the magnitude of thermally injected spin signal scales linearly with the power of local heating of electrodes, and its sign is reversed as we invert the temperature gradient. A large Hanle magnetothermopower (HMTP) of about 7.0% and the Seebeck spin tunneling coefficient of larger than 0.74 meV K 21 are obtained at room temperature.T he tremendous power consumption and accompanying heat generation in current electronic devices requires alternative technologies to provide a solution for the energy issues and to realize the energy efficient electronics. Spintronics is a viable route for it, using the spin degree of freedom in addition to the conventional charge transport 1 . Recently another important ingredient, namely heat, appears on the stage. It has been reported that the temperature gradient and heat flow in ferromagnetic structures gives rise to a variety of spin related phenomena 2 . Understanding the interplay between heat and spin transport is a fundamental and intriguing subject but also offers unique possibilities for emerging electronics based on the combination of thermoelectrics and spintronics.Especially in SC-based spintronics, the functional use of heat provides a new route to inject and control of spin in semiconductors (SCs) 3 . The generation of non-equilibrium spin populations (i.e. spin accumulation) in nonmagnetic SC is a central issue of SC-based spintronics 1,3-5 . Significant progress has been made on the spin accumulation in various SC systems by means of circularly polarized light 4,6 , spin-polarized tunneling 7-13 , hotelectron spin filtering 14,15 , spin-orbit interaction 16,17 , or magnetization dynamics 18,19 .Intriguingly, Le Breton et al. 20 have reported a rather different mechanism for the spin accumulation, in which temperature difference across a ferromagnet (FM)/oxide/SC tunnel contact can induce the spin accumulation (Dm) in SC via Seebeck spin tunneling (SST). It was found that the SST effect, involving thermal transfer of spin angular momentum from FM to SC without a tunneling charge current, is a purely interface-related phenomenon of the tunnel contact and governed by the energy dependence of its tunnel spin polarization (TSP) 20 . This provides a conceptually new mechanism for the generation of Dm in SC as well as for the functional use of heat in spintronic devices 20 . The SST and thermal spin accumulation (Dm th ) in p-type SC (e.g., p-type Si) have been intensely studied, using a Ni 80 Fe 20 /Al 2 O 3 /SiO 2 /p-SC contact with the asymmetry in TSP of tunneling holes 20 . However, the counterpart of n-type SC still needs to be explored...

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Quantum Interference Control of Ballistic Pure Spin Currents in Semiconductors

Cited by 284 publications

References 11 publications

Imaging mesoscopic spin Hall flow: Spatial distribution of local spin currents and spin densities in and out of multiterminal spin-orbit coupled semiconductor nanostructures

Imaging mesoscopic spin Hall flow: Spatial distribution of local spin currents and spin densities in and out of multiterminal spin-orbit coupled semiconductor nanostructures

Theory of thermal spin-charge coupling in electronic systems

Thermal Spin Injection and Accumulation in CoFe/MgO/n-type Ge Contacts

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