Quantum-Well-Induced Giant Spin-Orbit Splitting

Mathias, Stefan; Ruffing, Andreas; Deicke, F.; Wiesenmayer, M.; Sakar, I.; Bihlmayer, Gustav; Chulkov, Eugene V.; Koroteev, Yu. M.; Echenique, Pedro M.; Bauer, Michael; Aeschlimann, Martin

doi:10.1103/physrevlett.104.066802

Cited by 95 publications

(72 citation statements)

References 33 publications

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“…The essential requisite for the Rashba effect is that the spin degeneracy is lifted by the inversion symmetry-breaking (ISB) field in the presence of the spin-orbit coupling (SOC). To date, major concerns have focused on enlarging Rashba strength characterized by the Rashba coefficient α R (3,5,6). The controllability in the direction of the ISB field, on the other hand, has not been seriously considered.…”

mentioning

confidence: 99%

“…electronic structure | density functional theory | effective Hamiltonian T he Rashba effect has been widely investigated in 2D surfaces, interfaces, quantum wells, and 3D bulk systems (1)(2)(3)(4)(5)(6). The essential requisite for the Rashba effect is that the spin degeneracy is lifted by the inversion symmetry-breaking (ISB) field in the presence of the spin-orbit coupling (SOC).…”

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confidence: 99%

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Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

Kim

Im²,

Freeman

et al. 2014

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

276

306

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The Rashba effect is spin degeneracy lift originated from spinorbit coupling under inversion symmetry breaking and has been intensively studied for spintronics applications. However, easily implementable methods and corresponding materials for directional controls of Rashba splitting are still lacking. Here, we propose organic-inorganic hybrid metal halide perovskites as 3D Rashba systems driven by bulk ferroelectricity. In these materials, it is shown that the helical direction of the angular momentum texture in the Rashba band can be controlled by external electric fields via ferroelectric switching. Our tight-binding analysis and first-principles calculations indicate that S = 1=2 and J = 1=2 Rashba bands directly coupled to ferroelectric polarization emerge at the valence and conduction band edges, respectively. The coexistence of two contrasting Rashba bands having different compositions of the spin and orbital angular momentum is a distinctive feature of these materials. With recent experimental evidence for the ferroelectric response, the halide perovskites will be, to our knowledge, the first practical realization of the ferroelectric-coupled Rashba effect, suggesting novel applications to spintronic devices.electronic structure | density functional theory | effective Hamiltonian T he Rashba effect has been widely investigated in 2D surfaces, interfaces, quantum wells, and 3D bulk systems (1-6). The essential requisite for the Rashba effect is that the spin degeneracy is lifted by the inversion symmetry-breaking (ISB) field in the presence of the spin-orbit coupling (SOC). To date, major concerns have focused on enlarging Rashba strength characterized by the Rashba coefficient α R (3, 5, 6). The controllability in the direction of the ISB field, on the other hand, has not been seriously considered. In a surface or an interface, the potential gradient generated by the structural inversion asymmetry results in the loss of controllability; the field direction is mainly fixed according to the preformed surface or interface configuration. The situation is similar in recently discovered 3D Rashba material BiTeI (6), because this material has the compositional ISB field between Te and I layers.Controlling the ISB field and ultimately Rashba-type band splitting can be achieved by using a novel ferroelectric Rashba material (7,8). In a ferroelectric system, the bulk polarization controlled by external electric fields generates the ISB field. Therefore, the ferroelectric polarization directly couples to the spin splitting and the helical spin texture in the ferroelectric Rashba material, enabling the helicity reversal via the ferroelectric switching. Recent theoretical study suggested GeTe as a possible candidate for this mechanism, but the direct measurement of the ferroelectric polarization and switching is still missing due to the sizable conductivity of bulk GeTe (7,8).We consider organic-inorganic hybrid metal halide perovskites as promising ferroelectric Rashba materials. The general formula for this materia...

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mentioning

confidence: 99%

mentioning

confidence: 99%

Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

Kim

Im²,

Freeman

et al. 2014

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

276

306

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“…Thus, Rashba or spin-band splittings created in QWSs over nonmetallic substrates [17][18][19][20][21][22] are of great industrial potential. However, it is a great challenge to create a remarkable Rashba splitting in NM QWSs because of the strong screening effect in the metallic film.…”

Section: Introductionmentioning

confidence: 99%

Newtype large Rashba splitting in quantum well states induced by spin chirality in metal/topological insulator heterostructures

Chang

Jeng

2016

NPG Asia Mater

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In a two-dimensional system without inversion symmetry, such as a surface or interface, the potential-asymmetry-induced electric field can create the Rashba effect, which is spin-band splitting caused by spin-orbit coupling (SOC). On the basis of Rashba splitting, several promising spintronic devices, such as the Datta-Das spin transistor, have been designed for manipulating spin precession in the absence of a magnetic field. Rashba splitting can be created in several metal quantum well states (QWSs), such as in Pb/Si; however, the effect is usually moderate because the itinerant carriers within the metal film strongly screen out the electric field. A large Rashba splitting can be found in the unoccupied QWSs of the Bi monolayer on Cu (111); however, the metallic substrate limits the diversity of its applications. To achieve strong Rashba splitting in metal thin film based on an insulating substrate, which is most desirable, we propose the normal metal (NM)/topological insulator (TI) heterostructure for manufacturing Rashba-type splitting in NM QWSs. In such a hybrid system, the TI spin-momentum-locking Dirac surface state associated with SOC strongly modifies the penetration depth of the NM QWS into the TI substrate according to the spin orientation, leading to strong Rashba-type splittings in the NM QWS. Combining ab initio calculations and analytical modeling, the momentum separation of the Rashba splitting in the NM QWS can be as large as 0.18 Å − 1 , which is the largest ever found in metal-film/non-metallic substrate systems. Furthermore, the induced spin polarization in the Rashba band is nearly 100%, much higher than the typical value of 40-50% in the TI surface state itself. This remarkably large Rashba splitting and the high spin polarization in the NM QWS evoked by the spin chirality of the TI surface state confer great potential for the development of spintronic devices. INTRODUCTIONOne of the major tasks in the development of semiconductor spintronics is finding a material with remarkable Rashba-type splitting to control the spin current. For example, the Datta-Das spin transistor, 1 proposed for more than 20 years, switches the spin current by controlling the magnitude of Rashba splitting of a two-dimensional electron gas in a semiconductor heterostructure. [2][3][4][5][6] After decades of trials, the Datta-Das spin transistor has finally been experimentally realized recently. 7 However, the mild splitting of the two-dimensional electron gas bands is inapplicable for spin transistors working at room temperature or designed in the nanoscale. 7-9 A much more feasible approach is thus highly desirable.Alternatively, giant Rashba splittings can be found in the surface state (SS) of noble-metal-based surface alloys with strong spin-orbit couplings (SOCs) in heavy atoms. 10,11 The interatomic electric field at the surface-alloy plane is the key to the giant splitting. 12 Regarding the influence of the metal host, the SS would be hidden in the spintronics functions; therefore, efforts have been made on s...

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“…3 At metal surfaces, the electrons can be excited into the intrinsic surface states, 4,5 image potential states (IPSs), [6][7][8][9][10][11][12][13][14] quantum well states, [15][16][17][18][19] as well as in adsorbate-induced states. [20][21][22][23][24][25][26] Surface states originate from the crystal symmetry breaking near the surface and are localized in a few outermost atomic layers.…”

Section: Introductionmentioning

confidence: 99%

Green's function approach to the lifetimes of image potential resonances at metal surfaces

2013

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We present a theoretical study of the image potential resonances (IPRs) at metal surfaces. We develop the Green's functions approach allowing us to calculate binding energies E n and lifetimes τ n of IPRs with high quantum numbers n (up to 10 in this work). A systematic study is performed at the point for the close-packed metal surfaces: Cu(111), Ag(111), Au(111), Al(001), Al(111), Be(0001), Mg(0001), Na(110), Li (110), and also at the Y point on Cu(110). The calculated lifetimes of IPRs on close-packed surfaces demonstrate the scaling law τ n ∝ n 3 . Our results are in agreement with available experimental data. We show that at the Y point on Cu(110) each quantum number n corresponds to a pair of IPRs n + and n − , where the energy difference E n+ − E n− is proportional to n −3 . The lifetimes τ n+ and τ n− differ significantly, however, they both obey the scaling law τ n± ∝ n 3 . Since the electrons trapped in the long-lived IPRs are strongly localized on the vacuum side, we argue that the inelastic electron-electron and electron-phonon scattering have a small contribution to the decay rate of these IPRs. The latter is dominated by the resonant electron transfer into the bulk.

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Quantum-Well-Induced Giant Spin-Orbit Splitting

Cited by 95 publications

References 33 publications

Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

Newtype large Rashba splitting in quantum well states induced by spin chirality in metal/topological insulator heterostructures

Green's function approach to the lifetimes of image potential resonances at metal surfaces

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