Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads

Hamaya, Kohei; Masubuchi, Satoru; Kawamura, Minoru; Machida, Tomoki; Jung, Minkyung; Shibata, Kenji; Hirakawa, Kazuhiko; Taniyama, Tomoyasu; Ishida, Shintaro; Arakawa, Yasuhiko

doi:10.1063/1.2435957

Cited by 87 publications

(103 citation statements)

References 26 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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“…11͒ geometries composed of an insulator layer sandwiched by two ferromagnetic metallic leads, except for the quantum dot replacing the insulator layer. This system ͑dot coupled to FM leads͒ was recently experimentally realized in the context of semiconductor quantum dots 12,13 and molecules. [14][15][16] A wealth of spin-dependent effects has been observed in this system due to the interplay of quantum confinement, Coulomb correlations, Pauli principle, and leadpolarization alignments.…”

Section: Introductionmentioning

confidence: 99%

Spin-polarized current and shot noise in the presence of spin flip in a quantum dot via nonequilibrium Green’s functions

2008

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Using non-equilibrium Green functions we calculate the spin-polarized current and shot noise in a ferromagnet-quantum-dot-ferromagnet (FM-QD-FM) system. Both parallel (P) and antiparallel (AP) magnetic configurations are considered. Coulomb interaction and coherent spin-flip (similar to a transverse magnetic field) are taken into account within the dot. We find that the interplay between Coulomb interaction and spin accumulation in the dot can result in a bias-dependent current polarization ℘. In particular, ℘ can be suppressed in the P alignment and enhanced in the AP case depending on the bias voltage. The coherent spin-flip can also result in a switch of the current polarization from the emitter to the collector lead. Interestingly, for a particular set of parameters it is possible to have a polarized current in the collector and an unpolarized current in the emitter lead. We also found a suppression of the Fano factor to values well below 0.5.

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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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Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads

Cited by 87 publications

References 26 publications

Spin effects in single-electron tunnelling

Spin effects in single-electron tunnelling

Spin-polarized current and shot noise in the presence of spin flip in a quantum dot via nonequilibrium Green’s functions

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

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