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Hu, Chang‐Ming; Nitta, Junsaku; Akazaki, Tatsushi; Takayanagi, Hideaki; Ōsaka, Jiro; Pfeffer, P.; Zawadzki, W.

doi:10.1103/physrevb.60.7736

Cited by 196 publications

(110 citation statements)

References 19 publications

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“…It is instructive to consider the influence of possible nonparabolicity in the band structure described by a contribution to the Hamiltonian of higher order in the momentum. For instance, as it was argued theoretically [22] and confirmed experimentally [19], particularly large values of α are typically accompanied by a sizeable quartic nonparabolicity of the form ( p 2 ) 2 . This is due to the similar dependence of both terms on the band gap.…”

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confidence: 71%

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Nonballistic Spin-Field-Effect Transistor

2003

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We propose a spin field-effect transistor based on spin-orbit (s-o) coupling of both the Rashba and the Dresselhaus types. Differently from earlier proposals, spin transport through our device is tolerant against spin-independent scattering processes. Hence the requirement of strictly ballistic transport can be relaxed. This follows from a unique interplay between the Dresselhaus and the (gate-controlled) Rashba interactions; these can be tuned to have equal strengths thus yielding kindependent eigenspinors even in two dimensions. We discuss implementations with two-dimensional devices and quantum wires. In the latter, our setup presents strictly parabolic dispersions which avoids complications arising from anticrossings of different bands.In the recent years research in semiconductor physics has been focused on the emerging field of spintronics. This key word refers to the variety of efforts to use the electron spin rather than, or in combination with, its charge for information processing; or, even more ambitiously, quantum information processing [2]. Among the most prominent device proposals is the spin field-effect transistor (FET) due to Datta and Das [3]. This proposal uses the Rashba spin-orbit coupling to perform controlled rotations of spins of electrons passing through an FETtyped device. This particular spin-orbit interaction is due to the inversion-asymmetry of the confining potential and is of the form [4]where p is the momentum of the electron confined in a two-dimensional geometry, and σ the vector of Pauli matrices. The coefficient α is tunable in strength by the external gate of the FET. Due to the dependence on the momentum, the Rashba spin-orbit coupling can be viewed as a wave vector-dependent Zeeman field which can change drastically if the electron is scattered into a different momentum state. Therefore, such scattering events readily randomize the electron spin thus limiting the range of operation of the Datta-Das spin-FET to the regime of ballistic transport where such processes do not occur.In the present work we propose a modified version of the spin-FET in which the electrons are not only subject to spin-orbit interaction of the Rashba but also of the Dresselhaus type [5]. The latter is present in semiconductors lacking bulk inversion symmetry. When restricted to a two-dimensional semiconductor nanostruture with appropriate growth geometry this coupling is of the form [6,7] where the coefficient β is determined by the semiconductor material and the geometry of the sample. Below we show that our proposed device is robust against spin-independent scattering and hence can also operate in a non-ballistic (or diffusive) regime. This unique feature follows from the possibility of tuning the Rashba (via proper gating) and the Dresselhaus terms so that they have equal strengths α = β. In this case, we show quite generally below that the electron spinor is k-independent in two dimensions -even in the presence of (spin-independent) scatterers. Tuned Rashba and Dresselhaus terms. Consider the Ham...

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confidence: 71%

“…The largest values for α observed in III-V semiconductors are of the order of a few 0.1eVÅ [16][17][18][19][20][21]. An estimate for the Dresselhaus coefficient in a confined geometry is obtained from β = γ k 2 z , where k 2 z is the expectation value of the square wave vector component in the growth direction.…”

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confidence: 99%

Nonballistic Spin-Field-Effect Transistor

2003

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“…In addition, the M-shape of the VSBs, which is imposed by the VB dispersion, is expected to further decrease the Rashba splitting. Nonparabolicity effects have been found to reduce considerably the Rashba splitting especially for semiconductors with small bandgap, as it is the case for Bi 2 Se 3 [45][46][47].…”

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confidence: 99%

Origin of Rashba splitting in the quantized subbands at the Bi2Se3surface

et al. 2013

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We study the band structure of the Bi2Se3 topological insulator (111) surface using angle-resolved photoemission spectroscopy. We examine the situation where two sets of quantized subbands exhibiting different Rashba spin-splitting are created via bending of the conduction (CB) and the valence (VB) bands at the surface. While the CB subbands are strongly Rashba spin-split, the VB subbands do not exhibit clear spin-splitting. We find that CB and VB experience similar band bending magnitudes, which means, a spin-splitting discrepancy due to different surface potential gradients can be excluded. On the other hand, by comparing the experimental band structure to first principles LMTO band structure calculations, we find that the strongly spin-orbit coupled Bi 6p orbitals dominate the orbital character of CB, whereas their admixture to VB is rather small. The spinsplitting discrepancy is, therefore, traced back to the difference in spin-orbit coupling between CB and VB in the respective subbands' regions. 73, The narrow bandgap semiconductor Bi 2 Se 3 has been known for decades for its good thermoelectric properties [1,2]. The recent observation of a topologically protected surface state (TSS) in Bi 2 Se 3 [3, 4] marked the discovery of a model system for 3D topological insulators (TIs) and has lead to a surge of renewed interest in the properties of this material. The Bi 2 Se 3 (111) surface hosts within a gap of bulk bands projected onto the surface Brillouin zone (BZ) a single TSS with Dirac cone dispersion [3][4][5]. Similar TSS dispersion has been found in other Bi-based systems, such as, Bi 2 Te 3 and PbBi 2 Te 4 [4, 6]. The TSS is robust against scattering from non-magnetic perturbations. Moreover, it possesses a helical character, which infers a defined spin polarization for a particular momentum value. These characteristics might lend themselves to a variety of new applications, especially, in spintronics, where transport and manipulation of spin currents at high temperatures and with diminutive scattering interactions are sought out [7][8][9][10].It has already been shown that the modification of the Bi 2 Se 3 surface with non-magnetic adsorbates [4,[11][12][13][14], as well as heating up to 400 K [15] does not alter TSS protection. However, it dopes the TSS and can even change surface electronic properties. Surface n-doping creates two sets of new states at the surface, which appear simultaneously in the immediate vicinity of the TSS within the projected bulk conduction band (CB) and valence band (VB) regions. While parabolic bands with a large Rashba splitting are observed above the Dirac point (E D ), the bands below are M-shaped, can overlap with the TSS, and do not show a clear spin splitting. These two band sets have been mainly interpreted as quantized subbands resulting from the confinement of a pair of two-dimensional electron gases (2DEGs) at the surface created via CB and VB bending [13,14,[16][17][18]. Practically, the largely spin-split bands add a new feature to Bi 2 Se 3 surface for spintron...

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“…If the electron concentration is increased above a certain value, the second subband of the quantum well can be occupied, in addition. It was shown by Hu et al [20,21] that the Rashba coupling constant of the second subband differs from the coupling constant of the first subband. This might result in a weakening of the output signal of the spin transistor.…”

Section: Two-dimensional Structuresmentioning

confidence: 98%

Rashba effect in strained InGaAs/InP quantum wire structures

Schäpers

Knobbe

Hart

et al. 2003

Science and Technology of Advanced Materials

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We investigated the effect of the Rashba spin -orbit coupling in two-dimensional electron gases and quasi one-dimensional wire structures based on a strained InGaAs/InP heterostructure. For the two-dimensional electron gas structure it is demonstrated that the Rashba effect can be controlled by using a gate electrode. By a detailed discussion it is shown that our heterostructure can be employed for a spin transistor based on the Rashba effect [Appl. Phys. Lett. 56 (1990) 665]. The Rashba effect in quantum wire structures is studied by means of magnetotransport measurements. As for the two-dimensional case characteristic beating patterns were found for wire structures having a width down to 600 nm. Our results clearly show that Rashba spin-orbit coupling can directly be observed in quasi one-dimensional structures. q

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Zero-field spin splitting in an invertedIn0.53Ga0.47As

Cited by 196 publications

References 19 publications

Nonballistic Spin-Field-Effect Transistor

Nonballistic Spin-Field-Effect Transistor

Origin of Rashba splitting in the quantized subbands at the Bi2Se3surface

Rashba effect in strained InGaAs/InP quantum wire structures

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