Spin currents in superconductors

Hirsch, J. E.

doi:10.1103/physrevb.71.184521

Cited by 34 publications

(49 citation statements)

References 45 publications

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“…This novel phenomenon offers the exciting possibility of pure electric driven spintronics in semiconductors, which can be more readily integrated with current industry. Recently, the observations of the spin Hall effect have been reported [8,9,10] in GaAs based devices, which has generated an intensive research [11,12,13,14,15,16]. However, up to now, most of the experimental measurements were concentrated on GaAs system.…”

mentioning

confidence: 99%

Erratum: Current and Strain-Induced Spin Polarization inInGaN/GaNSuperlattices [Phys. Rev. Lett.98, 136403 (2007)]

Chang¹,

Chen²,

Chen³

et al. 2007

Phys. Rev. Lett.

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The lateral current-induced spin polarization in InGaN/GaN superlattices (SLs) without an applied magnetic field is reported. The fact that the sign of the nonequilibrium spin changes as the current reverses and is opposite for the two edges provides a clear signature for the spin Hall effect. In addition, it is discovered that the spin Hall effect can be strongly manipulated by the internal strains. A theoretical work has also been developed to understand the observed strain induced spin polarization. Our result paves an alternative way for the generation of spin polarized current.PACS numbers: 72.25.Dc, 78.20.Hp, 78.55.Cr It has been proposed theoretically that a transverse spin current, the so called spin Hall current, can be generated in strongly spin-orbit coupling systems by external electric field [1,2,3,4,5,6,7]. This novel phenomenon offers the exciting possibility of pure electric driven spintronics in semiconductors, which can be more readily integrated with current industry. Recently, the observations of the spin Hall effect have been reported [8,9,10] in GaAs based devices, which has generated an intensive research [11,12,13,14,15,16]. However, up to now, most of the experimental measurements were concentrated on GaAs system. More clear evidences to confirm the spin Hall effect in other semiconductors are still needed [17]. Nitride semiconductors probably represent the most studied material system in semiconductor community for the last decade. InGaN/GaN superlattices have become particularly attractive because of their wide applications in light-emitting diodes (LEDs) [18] and high efficiency laser diodes (LDs) [19]. In this letter, we provide the first experimental observation of currentinduced spin polarization in InGaN/GaN superlattices. In addition, we discover that the spin Hall effect can be strongly manipulated by the internal strains. In order to have a fundamental understanding of the strain-induced spin Hall effect, a theoretical investigation has also been performed. Because strains are commonly present in semiconductor multilayers and superlattices due to lattice mismatch, our result therefore provides a convenient way to control the magnitude of the spin Hall effect, which should be very useful for the future applications. Furthermore, this strain dependence enables to resolve the intensive debate about whether the intrinsic spin Hall effect remains valid beyond the ballistic transport regime.The n-type InGaN/GaN superlattices were grown by a horizontal flow metalorganic chemical vapor deposition on (0001) sapphire substrate. All structures consist of 30 nm buffer layer, followed by a 2 µm epitaxial GaN layer and then 50 periods of InGaN/GaN superlattices. Superlattices are composed of periods of alternating 30Å GaN barriers and 50Å In x Ga 1−x N wells with x ∼ 0.15. The superlattices was doped with Si, and the electron concentration is 2x10 12 cm −2 according to the Hall measurement. For the cross sectional photoluminescence (PL) measurement, the sample was excited by a He-Cd lase...

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mentioning

confidence: 99%

Erratum: Current and Strain-Induced Spin Polarization inInGaN/GaNSuperlattices [Phys. Rev. Lett.98, 136403 (2007)]

Chang¹,

Chen²,

Chen³

et al. 2007

Phys. Rev. Lett.

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“…This is consistent with absence of a charge current but it allows for the existence of a spin current, where electrons of opposite spin orbit in opposite directions. This is what happens in the superconducting state according to the theory of hole superconductivity [30,44,46]. Thus, within this theory there is no puzzle associated with inward radial motion of electrons in the rotating superconductor.…”

Section: E Radial Motion and Existence Of Spin Currentmentioning

confidence: 69%

“…This was the expectation of Becker et al [9], they stated: "Wir beschränken unsere Betrachtungen von vornherein auf die Rotationsbewegung der Elektronen, vernachlässigen also die dureh die Zentrifugalkraft bedingte negative Aufladung der Kugeloberflache", meaning "We restrict our considerations from the beginning to the rotational motion of the electrons, neglecting the negative charging of the surface caused by the centrifugal force". In references [28] and [29] it was also concluded that negative charges would move out because of an incorrect analysis of the radial forces involved [30], and the authors presumably did That physical intuition is in fact flawed for the case of a perfect conductor. A perfect conductor starting from rest would indeed develop a magnetic field as the electrons near the surface lag behind the motion of the ions, and the Lorentz force due to this magnetic field would pull the electrons slightly inward.…”

Section: The Radial Electric Fieldmentioning

confidence: 99%

The London moment: what a rotating superconductor reveals about superconductivity

Hirsch¹

2013

Phys. Scr.

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The London moment is the magnetic moment acquired by a rotating superconductor. We propose that the London moment reveals the following fundamental properties of the superconducting state: (i) superconductors (unlike normal metals) know the sign of the charge carriers, (ii) the superconducting charge carriers are f ree electrons, (iii) electrons are expelled from the interior to the surface in the transition to the superconducting state, (iv), superfluid electrons occupy orbits of radius 2λL (λL =London penetration depth), and (v) a spin current exists in the ground state of superconductors. These properties are consistent with the Meissner effect, however the Meissner effect does not directly reveal the sign of the charge carriers nor the fact that the carrier's mass is the free electron mass nor the fact that a spin current exists in superconductors. Note also that within the BCS theory of superconductivity none of the key properties of superconductors listed above are predicted. Instead, these properties are predicted by the theory of hole superconductivity.PACS numbers:

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“…The investigation of these effect is particularly interesting. The breaking of particle-hole symmetry, even at half filling, is a generic property of real materials and creates effects on the paramagnetic phase [15], besides the frustration of the antiferromagnetic phase [16]. The effect of nonrandom NNN hopping becomes evident already in the noninteracting system through an asymmetric density of states (DOS), as already derived for an arbitrary hopping on the Bethe lattice [17].…”

Section: Introductionmentioning

confidence: 73%

Anderson localization on Falicov-Kimball model with next-nearest-neighbor hopping and long-range correlated disorder

et al. 2008

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The phase diagram of correlated, disordered electron systems is calculated within dynamical mean-field theory for the Anderson-Falicov-Kimball model with nearest-neighbors and next-nearestneighbors hopping. The half-filled band is analyzed in terms of the chemical potential of the system using the geometric and arithmetic averages. We also introduce the on-site energies exhibiting a long-range correlated disorder, which generates a system with similar characteristics as the one created by a random independent variable distribution. A decrease in the correlated disorder reduces the extended phase.

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Spin currents in superconductors

Cited by 34 publications

References 45 publications

Erratum: Current and Strain-Induced Spin Polarization inInGaN/GaNSuperlattices [Phys. Rev. Lett.98, 136403 (2007)]

Erratum: Current and Strain-Induced Spin Polarization inInGaN/GaNSuperlattices [Phys. Rev. Lett.98, 136403 (2007)]

The London moment: what a rotating superconductor reveals about superconductivity

Anderson localization on Falicov-Kimball model with next-nearest-neighbor hopping and long-range correlated disorder

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