Spin relaxation in lateral quantum dots: Effects of spin-orbit interaction

Florescu, Marian; Hawrylak, Paweł

doi:10.1103/physrevb.73.045304

Cited by 61 publications

(53 citation statements)

References 52 publications

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“…In particular, Hanson et al found T 1 for the singlet-triplet transition in a two-electron GaAs dot to be 2.6 ms at B=0.02 T. We shall call this T ST . Extensive theoretical work has been done for T ST in GaAs 4,13,14,15,16 and our methods are similar to those found in these references.…”

Section: Introductionmentioning

confidence: 78%

Singlet-triplet relaxation in two-electron silicon quantum dots

2008

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We investigate the singlet-triplet relaxation process of a two electron silicon quantum dot. In the absence of a perpendicular magnetic field, we find that spin-orbit coupling is not the main source of singlet-triplet relaxation. Relaxation in this regime occurs mainly via virtual states and is due to nuclear hyperfine coupling. In the presence of an external magnetic field perpendicular to the plane of the dot, the spin-orbit coupling is important and virtual states are not required. We find that there can be strong anisotropy for different field directions: parallel magnetic field can increase substantially the relaxation time due to Zeeman splitting, but when the magnetic field is applied perpendicular to the plane, the enhancement of the spin-orbit effect shortens the relaxation time. We find the relaxation to be orders of magnitude longer than for GaAs quantum dots, due to weaker hyperfine and spin-orbit effects.

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Section: Introductionmentioning

confidence: 78%

Singlet-triplet relaxation in two-electron silicon quantum dots

2008

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“…In contrast to single-electron spin states in a quantum dot, the lowest two-electron spin states, singlet and triplet, are coupled directly by the spin-orbit interaction ͓ex-cept for T 0 and S, which are not coupled to lowest order in the spin-orbit interaction, due to spin selection rules ͑Dickmann and Hawrylak, 2003;Florescu and Hawrylak, 2006;Sasaki et al, 2006;Climente et al, 2007;Golovach et al, 2007͔͒. This is not so surprising since the singlet and triplet states themselves involve different orbitals.…”

Section: Spin-orbit Interaction In Quantum Dotsmentioning

confidence: 99%

Spins in few-electron quantum dots

et al. 2007

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The canonical example of a quantum-mechanical two-level system is spin. The simplest picture of spin is a magnetic moment pointing up or down. The full quantum properties of spin become apparent in phenomena such as superpositions of spin states, entanglement among spins, and quantum measurements. Many of these phenomena have been observed in experiments performed on ensembles of particles with spin. Only in recent years have systems been realized in which individual electrons can be trapped and their quantum properties can be studied, thus avoiding unnecessary ensemble averaging. This review describes experiments performed with quantum dots, which are nanometer-scale boxes defined in a semiconductor host material. Quantum dots can hold a precise but tunable number of electron spins starting with 0, 1, 2, etc. Electrical contacts can be made for charge transport measurements and electrostatic gates can be used for controlling the dot potential. This system provides virtually full control over individual electrons. This new, enabling technology is stimulating research on individual spins. This review describes the physics of spins in quantum dots containing one or two electrons, from an experimentalist's viewpoint. Various methods for extracting spin properties from experiment are presented, restricted exclusively to electrical measurements. Furthermore, experimental techniques are discussed that allow for ͑1͒ the rotation of an electron spin into a superposition of up and down, ͑2͒ the measurement of the quantum state of an individual spin, and ͑3͒ the control of the interaction between two neighboring spins by the Heisenberg exchange interaction. Finally, the physics of the relevant relaxation and dephasing mechanisms is reviewed and experimental results are compared with theories for spin-orbit and hyperfine interactions. All these subjects are directly relevant for the fields of quantum information processing and spintronics with single spins ͑i.e., single spintronics͒.

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“…[4][5][6] On the other hand, at higher fields ͑Teslas͒ the relaxation is due to phonon-induced spin-flip transitions. [7][8][9][10][11][12][13][14][15][16][17][18][19] These are allowed due to the presence of spin-orbit coupling. Variants of the phonon-induced spin relaxation has been proposed, such as ripple coupling, 20,21 important in very small quantum dots ͑10 nm͒, or fluctuations in spin-orbit parameters, important when underlying heterostructure inhomogeneities 22 are present.…”

Section: Introductionmentioning

confidence: 99%

Orbital and spin relaxation in single and coupled quantum dots

Stano

Fabian

2006

Phys. Rev. B

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Phonon-induced orbital and spin relaxation rates of single electron states in lateral single and double quantum dots are obtained numerically for realistic materials parameters. The rates are calculated as a function of magnetic field and interdot coupling, at various field and quantum dot orientations. It is found that orbital relaxation is due to deformation potential phonons at low magnetic fields, while piezoelectric phonons dominate the relaxation at high fields. Spin relaxation, which is dominated by piezoelectric phonons, in single quantum dots is highly anisotropic due to the interplay of the Bychkov-Rashba and Dresselhaus spin-orbit couplings. Orbital relaxation in double dots varies strongly with the interdot coupling due to the cyclotron effects on the tunneling energy. Spin relaxation in double dots has an additional anisotropy due to anisotropic spin hot spots which otherwise cause giant enhancement of the rate at useful magnetic fields and interdot couplings. Conditions for the absence of the spin hot spots in in-plane magnetic fields ͑easy passages͒ and perpendicular magnetic fields ͑weak passages͒ are formulated analytically for different growth directions of the underlying heterostructure. It is shown that easy passages disappear ͑spin hot spots reappear͒ if the double dot system loses symmetry by an xy-like perturbation.

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Spin relaxation in lateral quantum dots: Effects of spin-orbit interaction

Cited by 61 publications

References 52 publications

Singlet-triplet relaxation in two-electron silicon quantum dots

Singlet-triplet relaxation in two-electron silicon quantum dots

Spins in few-electron quantum dots

Orbital and spin relaxation in single and coupled quantum dots

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