Persistent sourcing of coherent spins for multifunctional semiconductor spintronics

Malajovich, I.; Berry, Joseph J.; Samarth, N.; Awschalom, D. D.

doi:10.1038/35081014

Cited by 216 publications

(110 citation statements)

References 12 publications

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“…We find that their effective g factor is highly anisotropic, giving a large Zeeman splitting of the acceptor states in a perpendicular field, whereas we cannot resolve any Zeeman splitting in in-plane fields up to 18 T. This giant anisotropy, which is much larger than in other systems [13][14][15][16], provides the possibility to tune the coupling of the holes to an external magnetic field by a gatecontrolled shift of the hole wave function [17] in spintronic devices.…”

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confidence: 64%

Giant Anisotropy of Zeeman Splitting of Quantum Confined Acceptors inSi/Ge

et al. 2006

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Shallow acceptor levels in Si=Ge=Si quantum well heterostructures are characterized by resonanttunneling spectroscopy in the presence of high magnetic fields. In a perpendicular magnetic field we observe a linear Zeeman splitting of the acceptor levels. In an in-plane field, on the other hand, the Zeeman splitting is strongly suppressed. This anisotropic Zeeman splitting is shown to be a consequence of the huge light-hole -heavy-hole splitting caused by a large biaxial strain and a strong quantum confinement in the Ge quantum well. DOI: 10.1103/PhysRevLett.96.086403 PACS numbers: 71.70.Fk, 71.18.+y, 73.21.Fg Spintronic and quantum computing [1,2] are novel device concepts relying on quantum mechanical coherence. Si=Ge-based systems are promising candidates offering long spin coherence times [3,4], fast operations, and a well-established record of scalable integration. These important properties are also crucial requirements [2,5,6] for implementing multiqubit operations in a future quantum computer. One concept that may form the technological basis of a quantum computer is the spin-resonance transistor (SRT) [7]. Vrijen et al. [8] proposed a SRT where the electron spin manipulation is realized using the change in g factor between Si-rich and Ge-rich environments of a Si=Ge heterostructure. However, engineering the g factor [9,10] in such systems is complicated by the fact that the electron states in Si are in the X valleys whereas in Ge the electrons are located in the L valleys [11]. This problem does not arise for the valence band states, as both Si and Ge have their valence band maximum at the ÿ point. Thus, valence band states in Si=Ge are a promising choice [12] for g-factor engineering in the search for spin manipulation.In this Letter we have analyzed the g factor of shallow acceptor levels in a Si=Ge heterostructure by resonanttunneling spectroscopy. We find that their effective g factor is highly anisotropic, giving a large Zeeman splitting of the acceptor states in a perpendicular field, whereas we cannot resolve any Zeeman splitting in in-plane fields up to 18 T. This giant anisotropy, which is much larger than in other systems [13][14][15][16], provides the possibility to tune the coupling of the holes to an external magnetic field by a gatecontrolled shift of the hole wave function [17] in spintronic devices.For a proper understanding of acceptor levels it is essential to take into account the fourfold degeneracy of the valence band at the ÿ point (Fig. 1) which reflects the fact that the bulk valence band edge in these materials is characterized by an effective angular momentum J 3=2 [18,19]. As the symmetry of the crystal is reduced due to biaxial strain and a confinement potential, the degenerate states split into heavy-hole (HH) subbands with J z 3=2 and light-hole (LH) subbands with J z 1=2. Here, the quantization axis for the angular momentum is the z axis perpendicular to the epitaxial layer. So both parameters, the confinement potential, and the built-in strain substantially influence th...

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confidence: 64%

Giant Anisotropy of Zeeman Splitting of Quantum Confined Acceptors inSi/Ge

et al. 2006

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“…In fact, nearly ballistic motion is observed for the injected electrons close to the contact. This distinguishes the Schottky structure from another promising design to achieve efficient spin-polarized injection, the magneticsemiconductor/nonmagnetic-semiconductor p-n junction [59,60]. In the latter case, driftdiffusion (i.e.…”

Section: Discussionmentioning

confidence: 99%

Monte Carlo modeling of spin injection through a Schottky barrier and spin transport in a semiconductor quantum well

Shen

Saikin

Cheng

2004

Journal of Applied Physics

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We develop a Monte Carlo model to study injection of spin-polarized electrons through a Schottky barrier from a ferromagnetic metal contact into a non-magnetic low-dimensional semiconductor structure. Both mechanisms of thermionic emission and tunneling injection are included in the model. Due to the barrier shape, the injected electrons are non-thermalized. Spin dynamics in the semiconductor heterostructure is controlled by the Rashba and Dresselhaus spinorbit interactions and described by a single electron spin density matrix formalism. In addition to the linear term, the third order term in momentum for the Dresselhaus interaction is included.Effect of the Schottky potential on the spin dynamics in a 2 dimensional semiconductor device channel is studied. It is found that the injected current can maintain substantial spin polarization to a length scale in the order of 1 micrometer at room temperature without external magnetic fields. 72.25Dc, 72.25.Hg, 72.25Rb, 2 PACS:

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“…Particularly relevant is the question of whether spin phase is conserved during spin injection. Malajovich et al (2001) showed, by studying spin evolution in transport through a n-GaAs/n-ZnSe heterostructure, that the phase can indeed be preserved.…”

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confidence: 99%

Spintronics: Fundamentals and applications

2004

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Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics. CONTENTS

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Persistent sourcing of coherent spins for multifunctional semiconductor spintronics

Cited by 216 publications

References 12 publications

Giant Anisotropy of Zeeman Splitting of Quantum Confined Acceptors inSi/Ge

Giant Anisotropy of Zeeman Splitting of Quantum Confined Acceptors inSi/Ge

Monte Carlo modeling of spin injection through a Schottky barrier and spin transport in a semiconductor quantum well

Spintronics: Fundamentals and applications

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