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Lo, Ikai; Tsai, Jenn-Kai; Yao, Weizhen; Ho, P. C.; Tu, Li‐Wei; Chang, Tzu-Feng; Elhamri, S.; Mitchel, W. C.; Hsieh, Kuang-Yeu; Huang, J.; Huang, Hsuan‐Jung; Tsai, Wen–Chung

doi:10.1103/physrevb.65.161306

Cited by 93 publications

(34 citation statements)

References 14 publications

(3 reference statements)

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“…6,8 Currently, active experimental work on SO properties of microstructures including the wurtzite modifications of InAs, 44 InN, 45 GaN, [46][47][48] etc., is under way, and large SO splittings up to 9 meV have been reported. 47 Following the initial calculations of the band structure of wurtzite-type compounds, 49 more general models have been developed recently, 50,51 and it looks like the band folding in the hexagonal direction ͑resulting from the different size of the elementary cells in the zinc blende and wurtzite lattices͒ plays a role in developing large spin splittings. 52 Therefore, the Hamiltonian Ĥ R will be applied for arbitrary n , n 0.…”

Section: Dmentioning

confidence: 99%

Theory of electric dipole spin resonance in a parabolic quantum well

Éfros

Rashba

2006

Phys. Rev. B

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A theory of electric dipole spin resonance ͑EDSR͒, that is caused by various mechanisms of spin-orbit coupling, is developed as applied to free electrons in a parabolic quantum well. Choosing a parabolic shape of the well has allowed us to find explicit expressions for the EDSR intensity and its dependence on the magnetic field direction in terms of the basic parameters of the Hamiltonian. By using these expressions, we have investigated and compared the effect of specific mechanisms of spin orbit ͑SO͒ coupling and different polarizations of ac electric field on the intensity of EDSR. It is our basic assumption that the SO coupling energy is small compared with all different competing energies ͑the confinement energy, and the cyclotron and Zeeman energies͒ that allowed us to describe all SO coupling mechanisms in the framework of the same general approach. For this purpose, we have developed an operator formalism for calculating matrix elements of the transitions between different quantum levels. To make these calculations efficient enough and to derive explicit and concise expressions for the EDSR intensity, we have established a set of remarkable identities relating the eigenfrequencies and the angles defining the spatial orientation of the quantizing magnetic field B͑ , ͒. Applicability of these identities is not restricted by EDSR and we expect them to be useful for the general theory of parabolic quantum wells. The angular dependences of the EDSR intensity, found for various SO coupling mechanisms, show a fine structure consisting of alternating up and down cusps originating from repopulating different quantum levels and their spin sublevels. Angular dependences of the EDSR intensity are indicative of the relative contributions of the competing mechanisms of SO coupling. Our results show that electrical manipulating electron spins in quantum wells is generally highly efficient, especially by an in-plane ac electric field.

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Section: Dmentioning

confidence: 99%

Theory of electric dipole spin resonance in a parabolic quantum well

Éfros

Rashba

2006

Phys. Rev. B

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“…A few preliminary experiments have considered spin-orbit coupling for the twodimensional electron gas (2DEG) [9,10,11,12] in a narrow parameter space of high density and low mobility. The influence of spin-orbit coupling in the limit of low 2DEG density and high mobility has not been addressed.…”

mentioning

confidence: 99%

Large Bychkov-Rashba spin-orbit coupling in high-mobilityGaN∕AlxGa1−xN
Schmult¹,
Manfra²,
Punnoose³
et al. 2006
Phys. Rev. B
81
4
55
1
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We present low temperature magnetoconductivity measurements of a density-tunable and high mobility two-dimensional electron gas confined in the wide bandgap GaN/AlGaN system. We observed pronounced anti-localization minima in the low-field conductivity, indicating the presence of strong spin-orbit coupling. Density dependent measurements of magnetoconductivity indicate that the coupling is mainly due to the Bychkov-Rashba mechanism. In addition, we have derived a closed-form expression for the magnetoconductivity, allowing us to extract reliable transport parameters for our devices. The Rashba spin-orbit coupling constant is αso ∼ 6× 10 −13 eVm, while the conduction band spin-orbit splitting energy amounts to ∆so ∼ 0.3meV at ne=1×10 16 m −2 .GaN has emerged as a leading material for a variety of new device applications, ranging from solid-state, ultra-violet optical sources to high power electronics [1]. While the performance of many devices fabricated from GaN has been stunning, several fundamental physical processes remain to be understood. A prime example is spin-orbit coupling in GaN and its heterostructures. The burgeoning field of spintronics has invigorated the study of spin-orbit coupling in semiconducting materials [2,3]. To date, much experimental effort has been devoted to narrow bandgap material systems (InAs, InGaAs, GaAs, etc) as spin-orbit coupling is expected to be strong in these systems. Conversely, far less experimental effort has been directed toward wide bandgap systems like GaN in which spin-orbit effects are predicted to be suppressed by the large fundamental bandgap, E g , and reduced spinorbit splitting, ∆ 0 , of the valence band at zone center. Indeed, in the k·p formalism [4], the bare Rashba spinorbit coupling constant for electrons, α 0 , scales as: α 0 ∼ ∆ 0 /E 2 g . As the value of ∆ 0 for GaAs exceeds that of GaN by a factor of 30, it is reasonable to suspect that spin splitting of the conduction band in GaN-based heterostructures would be insignificant compared to GaAs and other narrow gap heterostructures.Spin-orbit coupling for conduction band electrons in bulk GaN was considered by Krishnamurthy [5] who calculated that the spin relaxation times in bulk GaN should exceed the spin relaxation time in GaAs by three orders of magnitude, thus making GaN an excellent candidate for transport of spin polarized currents over macroscopic distances. However, in Ref.[5] GaN was assumed to have the zinc-blende lattice structure. GaN is typically grown in the more stable wurtzite phase. It is known that the symmetry of the underlying crystal has a profound impact on spin-orbit induced splittings in the conduction band [6,7]. While the work of Ref.[5] is suggestive, very few experimental results for bulk wurtzite GaN have been reported [8] and the impact of spin-orbit coupling on transport in wurtzite GaN/AlGaN heterostructures remains an open question. A few preliminary experiments have considered spin-orbit coupling for the twodimensional electron gas (2DEG) [9,10,11,12] in a narrow paramet...

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“…7,8 For some AlGaN / GaN heterostructures a characteristic beating pattern was observed in the magnetoresistance, which was interpreted as the presence of the Rashba effect. [9][10][11][12] In addition to the Rashba effect, the lack of inversion symmetry in zincblende-type or wurtzite-type semiconductors can also alter the spin orientation during the electron propagation ͑Dresselhaus term͒. 13 The question to which extent spin-orbit coupling affects the electron transport in an AlGaN / GaN 2DEG is still not solved completely.…”

mentioning

confidence: 99%

Weak antilocalization in a polarization-doped AlxGa1−xN∕GaN heterostructure with single subband occupation

Thillosen

Schäpers

Kaluza

et al. 2006

Applied Physics Letters

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Spin-orbit scattering in a polarization-doped Al 0.30 Ga 0.70 N / GaN two-dimensional electron gas with one occupied subband is studied at low temperatures. At low magnetic fields weak antilocalization is observed, which proves that spin-orbit scattering occurs in the two-dimensional electron gas. From measurements at various temperatures the elastic scattering time tr , the dephasing time , and the spin-orbit scattering time so are extracted. Measurements in tilted magnetic fields were performed, in order to separate spin and orbital effects. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2162871͔ GaN-based layer systems are very interesting candidates regarding the realization of future spin-based electronics ͑spintronics͒. The interest in this material for spintronics was ignited by the theoretical prediction that diluted magnetic semiconductor based on GaN should show Curie temperatures above room temperature. 1 GaN-based diluted magnetic semiconductors are promising materials for spin injection because of their expected good matching to AlGaN / GaN heterostructures. However, for a successful realization of spintronic devices an essential prerequisite is that the spin orientation can be controlled externally. A prominent example is the spin transistor proposed by Datta and Das. 2 Here, the spin orientation in a two-dimensional electron gas ͑2DEG͒ is controlled by a gate electrode via the Rashba spin-orbit coupling originating from a macroscopic electric field in an asymmetric quantum well. 3 For semiconductor quantum wells with a large band gap channel layer, i.e., GaN, it is not obvious that the Rashba effect is suffciently strong, because the Rashba coupling parameter ␣ decreases with increasing band gap. However, recently it was shown theoretically that owing to the polarization field at the AlGaN / GaN heterointerface and owing to the large carrier concentration a relatively large Rashba spinsplitting energy can be expected. 4 Experimentally information on the Rashba effect can be obtained from the characteristic beating pattern in the Shubnikov-de Haas oscillations 5,6 or by analyzing weak antilocalization. 7,8 For some AlGaN / GaN heterostructures a characteristic beating pattern was observed in the magnetoresistance, which was interpreted as the presence of the Rashba effect. [9][10][11][12] In addition to the Rashba effect, the lack of inversion symmetry in zincblende-type or wurtzite-type semiconductors can also alter the spin orientation during the electron propagation ͑Dresselhaus term͒. 13 The question to which extent spin-orbit coupling affects the electron transport in an AlGaN / GaN 2DEG is still not solved completely. One reason is, that the observation of beating effects in the Shubnikov-de Haas oscillations is not an unambiguous signature for the presence of spin-orbit coupling. 11,14 In contrast, we focused on analyzing weak antilocalization at very low magnetic fields in a polarizationdoped AlGaN / GaN heterostructure which is a unambiguous indication of spin-orbit effects. Randomi...

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Spin splitting in modulation-dopedAlxGa1−xN/
Ikai Lo
¹
,
Jenn-Kai Tsai
²
,
Weizhen Yao
³

et al.

Cited by 93 publications

References 14 publications

Theory of electric dipole spin resonance in a parabolic quantum well

Theory of electric dipole spin resonance in a parabolic quantum well

Large Bychkov-Rashba spin-orbit coupling in high-mobilityGaN∕AlxGa1−xN
Schmult¹,
Manfra²,
Punnoose³
et al. 2006
Phys. Rev. B
81
4
55
1
View full text Add to dashboard Cite

Weak antilocalization in a polarization-doped AlxGa1−xN∕GaN heterostructure with single subband occupation

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Spin splitting in modulation-dopedAlxGa1−xN/Ikai Lo1, Jenn-Kai Tsai2, Weizhen Yao3 et al.

Cited by 93 publications

References 14 publications

Theory of electric dipole spin resonance in a parabolic quantum well

Theory of electric dipole spin resonance in a parabolic quantum well

Large Bychkov-Rashba spin-orbit coupling in high-mobilityGaN∕AlxGa1−xNSchmult1, Manfra2, Punnoose3 et al. 2006Phys. Rev. B814551View full textAdd to dashboardCite

Weak antilocalization in a polarization-doped AlxGa1−xN∕GaN heterostructure with single subband occupation

Contact Info

Product

Resources

About

Spin splitting in modulation-dopedAlxGa1−xN/
Ikai Lo
¹
,
Jenn-Kai Tsai
²
,
Weizhen Yao
³

et al.

Large Bychkov-Rashba spin-orbit coupling in high-mobilityGaN∕AlxGa1−xN
Schmult¹,
Manfra²,
Punnoose³
et al. 2006
Phys. Rev. B
81
4
55
1
View full text Add to dashboard Cite