Oscillatory changes in the tunneling magnetoresistance effect in semiconductor quantum-dot spin valves

Hamaya, Kohei; Kitabatake, Makoto; Shibata, Kenji; Jung, Minkyung; Kawamura, Minoru; Ishida, Shintaro; Taniyama, Tomoyasu; Hirakawa, Kazuomi; Arakawa, Yasuhiko; Machida, Tomoki

doi:10.1103/physrevb.77.081302

Cited by 61 publications

(66 citation statements)

References 32 publications

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“…aluminum) nanoparticles [41], single molecules [51], granular structures [163], self-assembled dots in ferromagnetic semiconductors [46], carbon nanotubes [52,53,54,55,56,57,58,59,60,61,62], and magnetic tunnel junctions [49]. Quite recently, semiconductor quantum dots based on two-dimensional electron gas were successfully attached to ferromagnetic leads [42,43,44,45].…”

Section: Spin Polarized Transport Through Single-level Quantum Dots Cmentioning

confidence: 99%

“…To observe the discrete electronic states in transport characteristics one should either diminish size of the metallic nanoparticles [41], or use semiconducting quantum dots based on two-dimensional electron gas [42,43,44,45]. An alternative strategy is to use ferromagnetic semiconducting materials instead of metallic ones as the electrodes [46].…”

Section: Introductionmentioning

confidence: 99%

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Spin effects in single-electron tunnelling

Barnaś¹,

Weymann²

2008

J. Phys.: Condens. Matter

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Abstract. An important consequence of the discovery of giant magnetoresistance in metallic magnetic multilayers is a broad interest in spin dependent effects in electronic transport through magnetic nanostructures. An example of such systems are tunnel junctions -single-barrier planar junctions or more complex ones. In this review we present and discuss recent theoretical results on electron and spin transport through ferromagnetic mesoscopic junctions including two or more barriers. Such systems are also called ferromagnetic single-electron transistors. We start from the situation when the central part of a device has the form of a magnetic (or nonmagnetic) metallic nanoparticle. Transport characteristics reveal then single-electron charging effects, including the Coulomb staircase, Coulomb blockade, and Coulomb oscillations. Single-electron ferromagnetic transistors based on semiconductor quantum dots and large molecules (especially carbon nanotubes) are also considered. The main emphasis is placed on the spin effects due to spin-dependent tunnelling through the barriers, which gives rise to spin accumulation and tunnel magnetoresistance. Spin effects also occur in the current-voltage characteristics, (differential) conductance, shot noise, and others. Transport characteristics in the two limiting situations of weak and strong coupling are of particular interest. In the former case we distinguish between the sequential tunnelling and cotunnelling regimes. In the strong coupling regime we concentrate on the Kondo phenomenon, which in the case of transport through quantum dots or molecules leads to an enhanced conductance and to a pronounced zero-bias Kondo peak in the differential conductance.

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Section: Spin Polarized Transport Through Single-level Quantum Dots Cmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spin effects in single-electron tunnelling

Barnaś¹,

Weymann²

2008

J. Phys.: Condens. Matter

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“…Furthermore, such systems are also being considered for applications in future spintronic devices as well as for quantum computing [21]. However, most of existing theoretical considerations of spin-dependent transport in quantum dots involved only single and double dot systems [3,4,5,6,7,8,9,10,11,12,13,14,15,16], while experiments were carried out mainly for single dot structures [22,23,24,25,26,27,28,29,30,31]. In particular, it has been shown [7] that the TMR in quantum dots weakly coupled to ferromagnetic leads is generally smaller than the value given by the Julliere model [1], TMR Jull = 2p 2 /(1 − p 2 ), where p is the spin polarization of the leads, which is characteristic of tunneling through a single tunnel junction.…”

Section: Introductionmentioning

confidence: 99%

The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads

Weymann

2009

J. Phys.: Condens. Matter

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Abstract. We analyze numerically the spin-dependent transport through coherent chains of three coupled quantum dots weakly connected to external magnetic leads. In particular, using the diagrammatic technique on the Keldysh contour, we calculate the conductance, shot noise and tunnel magnetoresistance (TMR) in the sequential and cotunneling regimes. We show that transport characteristics greatly depend on the strength of the interdot Coulomb correlations, which determines the spacial distribution of electron wave function in the chain. When the correlations are relatively strong, depending on the transport regime, we find both negative TMR as well as TMR enhanced above the Julliere value, accompanied with negative differential conductance (NDC) and super-Poissonian shot noise. This nontrivial behavior of tunnel magnetoresistance is associated with selection rules that govern tunneling processes and various high-spin states of the chain that are relevant for transport. For weak interdot correlations, on the other hand, the TMR is always positive and not larger than the Julliere TMR, although super-Poissonian shot noise and NDC can still be observed.

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“…(63). Thus, as in the case of the magnetization dynamics, the time scale of the coherent current pulse is much shorter than for the incoherent dynamics.…”

Section: Current Dynamicsmentioning

confidence: 91%

Theory of box-model hyperfine couplings and transport signatures of long-range nuclear-spin coherence in a quantum-dot spin valve

Chesi

Coish

2015

Phys. Rev. B

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We have theoretically analyzed coherent nuclear-spin dynamics induced by electron transport through a quantum-dot spin valve. The hyperfine interaction between electron and nuclear spins in a quantum dot allows for the transfer of angular momentum from spin-polarized electrons injected from ferromagnetic or half-metal leads to the nuclear spin system under a finite voltage bias. Accounting for a local nuclear-spin dephasing process prevents the system from becoming stuck in collective dark states, allowing a large nuclear polarization to be built up in the long-time limit. After reaching a steady state, reversing the voltage bias induces a transient current response as the nuclear polarization is reversed. Long-range nuclear-spin coherence leads to a strong enhancement of spinflip transition rates (by an amount proportional to the number of nuclear spins) and is revealed by an intense current burst, analogous to superradiant light emission. The crossover to a regime with incoherent spin flips occurs on a relatively long time scale, on the order of the single-nuclearspin dephasing time, which can be much longer than the time scale for the superradiant current burst. This conclusion is confirmed through a general master equation. For the two limiting regimes (coherent/incoherent spin flips) the general master equation recovers our simpler treatment based on rate equations, but is also applicable at intermediate dephasing. Throughout this work we assume uniform hyperfine couplings, which yield the strongest coherent enhancement. We propose realistic strategies, based on isotopic modulation and wavefunction engineering in core-shell nanowires, to realize this analytically solvable "box-model" of hyperfine couplings.

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Oscillatory changes in the tunneling magnetoresistance effect in semiconductor quantum-dot spin valves

Cited by 61 publications

References 32 publications

Spin effects in single-electron tunnelling

Spin effects in single-electron tunnelling

The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads

Theory of box-model hyperfine couplings and transport signatures of long-range nuclear-spin coherence in a quantum-dot spin valve

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