Temperature independence of the spin-injection efficiency of a MgO-based tunnel spin injector

Salis, G.; Wang, R.; Jiang, Xin; Shelby, R. M.; Parkin, S. S. P.; Bank, Seth R.; Harris, James S.

doi:10.1063/1.2149369

Cited by 96 publications

(64 citation statements)

References 14 publications

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“…The peak polarization P 0 is attributed to the spin polarization of the photocarriers and the anisotropic magnetization resistance of the FM electrodes superimposed by the efficiency of the spininjection junction. If we assume that the detected polarization is a simple product of the spin polarization of electrons at Fermi level of cobalt electrodes at 0.4, the (up-bound) efficiency of the spin injection η at 0.7 (35), and the photocurrent spin polarization, the spin polarization of the photocurrent is estimated to be 54% (low-bound), surpassing all demonstrated in conventional semiconductors.…”

Section: Resultsmentioning

confidence: 99%

Manipulating spin-polarized photocurrents in 2D transition metal dichalcogenides

Xie

Cui

2016

Proc. Natl. Acad. Sci. U.S.A.

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Manipulating spin polarization of electrons in nonmagnetic semiconductors by means of electric fields or optical fields is an essential theme of the conceptual nonmagnetic semiconductor-based spintronics. Here we experimentally demonstrate an electric method of detecting spin polarization in monolayer transition metal dichalcogenides (TMDs) generated by circularly polarized optical pumping. The spin-polarized photocurrent is achieved through the valleydependent optical selection rules and the spin-valley locking in monolayer WS 2 , and electrically detected by a lateral spin-valve structure with ferromagnetic contacts. The demonstrated long spinvalley lifetime, the unique valley-contrasted physics, and the spinvalley locking make monolayer WS 2 an unprecedented candidate for semiconductor-based spintronics.monolayer transition metal dichalcogenides | spin-valley coupling | spintronics | spin lifetime | valley lifetime A longtime focus in nonmagnetic semiconductor spintronics research is to explore methods to generate and manipulate spin of electrons by means of electric fields or optical fields instead of magnetic fields, enabling scalable and integrated devices (1). The present efforts follow two distinct paths. One uses spin Hall effect or optical pumping in III-V semiconductors which feature a significant spin-orbit coupling in a form of Dresselhaus and/or Rashba terms (2-4); the other focuses on spin transport [usually generated by spin injection from ferromagnetic (FM) electrodes] in semiconductor structures made of silicon (5), carbon nanotube (6), graphene (7), etc. which have long spin-coherence length due to weak spin-orbit coupling. The emergence of atomic two-dimensional group VI transition metal dichalcogenides (TMDs) MX 2 (M = Mo, W; X = S, Se), featuring nonzero but contrasting Berry curvatures at inequivalent K and K′ (equivalent to −K) valleys and unique spin-valley locking, provides an alternative pathway toward spintronics (8).Valleys refer to the energy extremes around the high symmetry points of the Brillouin zone, either a "valley" in the conduction band or a "hill" in the valence band. Owing to their hexagonal lattices, the family of TMDs has degenerate but inequivalent K(K′) valleys well separated in the first Brillouin zone. This gives electrons an extra valley degree of freedom, in addition to charge and spin. In monolayer TMDs the inversion symmetry breaking of crystal structures gives rise to nonzero but contrasting Berry curvatures at K and K′ valley which are a characteristic of the Bloch bands and could be recognized as a form of orbital magnetic moment of Bloch electrons (9-11). These contrasting Berry curvatures of electrons (holes) at K(K′) valleys lead to contrasting response to certain stimulus (9-19). One example is the valley Hall effect: An electric field would drive the electrons at different valleys (K and K′) toward opposite transverse directions, in a similar way as in spin Hall effect (10,20). A more pronounced manifestation is valley-dependent circular optical selectio...

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Section: Resultsmentioning

confidence: 99%

Manipulating spin-polarized photocurrents in 2D transition metal dichalcogenides

Xie

Cui

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…) and I(σ − ) the intensity of right-and left-handed EL component, respectively, was P CP ∼ 0.3 ∼ 0.35 at RT in the external magnetic flux of B = 0.8 T, which was achieved in the context of studying the spinfiltering effect of the MgO TB (18,19). Most of the past works regarding spin-LED were carried out under the vertical arrangement with low J ranging from 0.1 to 1 A/cm 2 and forcing spins aligned vertically by applying out-of-plane external magnetic fields (20).…”

mentioning

confidence: 99%

Pure circular polarization electroluminescence at room temperature with spin-polarized light-emitting diodes

Nishizawa

Nishibayashi

Munekata

2017

Proc. Natl. Acad. Sci. U.S.A.

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We report the room-temperature electroluminescence (EL) with nearly pure circular polarization (CP) from GaAs-based spinpolarized light-emitting diodes (spin-LEDs). External magnetic fields are not used during device operation. There are two small schemes in the tested spin-LEDs: first, the stripe-laser-like structure that helps intensify the EL light at the cleaved side walls below the spin injector Fe slab, and second, the crystalline AlO x spin-tunnel barrier that ensures electrically stable device operation. The purity of CP is depressively low in the low current density (J) region, whereas it increases steeply and reaches close to the pure CP when J > 100 A/cm 2 . There, either right-or left-handed CP component is significantly suppressed depending on the direction of magnetization of the spin injector. Spin-dependent reabsorption, spin-induced birefringence, and optical spin-axis conversion are suggested to account for the observed experimental results.A s well represented by the giant magnetoresistance, tunneling magnetoresistance, and spin-transfer-torque magnetic random access memory, spintronics research based on spin transport in magnetic metals has been contributing significantly in the progress of electronics through the advancement in recording bit density and low-power memory retention (1, 2). Proposal of the spin-current modulation with an electric field (3) and invention of diluted magnetic III-V semiconductors (4) have opened the opportunity of introducing spin degree of freedom in semiconductor technology (5). After those works, light-induced magnetism (6), electric-field-controlled magnetism (7), spin qubits in semiconductors (8, 9), spin-polarized light-emitting diodes (spinLEDs) (10, 11), and spin-metal-oxide-semiconductor field-effect transistor (12) were either demonstrated or proposed, which have caused an impact on the metal-based spintronics and applied physics that is not small. However, works that assure the roomtemperature (RT) operation of those semiconductor-based devices have not been accomplished to date.Concerning spin-LEDs, studies on a spin injector consisting of a ferromagnetic metal (FmM) and a tunnel barrier (TB) (13-15) succeeded those using semiconductor-based spin injectors (10, 11). The idea of the FmM-TB injector is to take advantage of spin-polarized carriers at RT with FmM and to simultaneously suppress with the TB the backward flow of unpolarized carriers that is unavoidable in the diffusive transport (16, 17). Many works have been carried out with the FmM-TB injector since then. Among those, the highest circular polarization (CP) value,) and I(σ − ) the intensity of right-and left-handed EL component, respectively, was P CP ∼ 0.3 ∼ 0.35 at RT in the external magnetic flux of B = 0.8 T, which was achieved in the context of studying the spinfiltering effect of the MgO TB (18,19). Most of the past works regarding spin-LED were carried out under the vertical arrangement with low J ranging from 0.1 to 1 A/cm 2 and forcing spins aligned vertically by applying out-of-pla...

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“…In zincblende semiconductors a number of such materials are already available [41,[80][81][82][83]. In addition to demonstrating that Fe 3 O 4 nanomagnets are suitable for wurtzite spin lasers [29], many other opportunities could be explored.…”

Section: Discussionmentioning

confidence: 99%

Wurtzite spin lasers

Faria

Chen

et al. 2017

Phys. Rev. B

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Semiconductor lasers are strongly altered by adding spin-polarized carriers. Such spin lasers could overcome many limitations of their conventional (spin-unpolarized) counterparts. While the vast majority of experiments in spin lasers employed zinc-blende semiconductors, the room temperature electrical manipulation was first emonstrated in wurtzite GaN-based lasers. However, the underlying theoretical description of wurtzite spin lasers is still missing. To address this situation, focusing on (In,Ga)N-based wurtzite quantum wells, we develop a theoretical framework in which the calculated microscopic spin-dependent gain is combined with a simple rate equation model. A small spin-orbit coupling in these wurtzites supports simultaneous spin polarizations of electrons and holes, providing unexplored opportunities to control spin lasers. For example, the gain asymmetry, as one of the key figures of merit related to spin amplification, can change the sign by simply increasing the carrier density. The lasing threshold reduction has a nonmonotonic depenedence on electron spin polarization, even for a nonvanishing hole spin polarization.

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Temperature independence of the spin-injection efficiency of a MgO-based tunnel spin injector

Cited by 96 publications

References 14 publications

Manipulating spin-polarized photocurrents in 2D transition metal dichalcogenides

Manipulating spin-polarized photocurrents in 2D transition metal dichalcogenides

Pure circular polarization electroluminescence at room temperature with spin-polarized light-emitting diodes

Wurtzite spin lasers

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