Interference effects in resonant magnetotransport

Mozyrsky, Dmitry; Fedichkin, Leonid; Gurvitz, S. A.; Berman, G. P.

doi:10.1103/physrevb.66.161313

Cited by 69 publications

(93 citation statements)

References 26 publications

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“…This includes normal or ferromagnetic metallic islands coupled to ferromagnetic leads [4,5] as well as spin-dependent transport from ferromagnets through QDs [6,7,8]. Precession of a single magnetic atom spin in an external magnetic field has been detected, but only in the power spectrum of the tunneling current [9,10].…”

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confidence: 99%

Interaction-Driven Spin Precession in Quantum-Dot Spin Valves

2003

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We analyze spin-dependent transport through spin valves composed of an interacting quantum dot coupled to two ferromagnetic leads. The spin on the quantum dot and the linear conductance as a function of the relative angle θ of the leads' magnetization directions is derived to lowest order in the dot-lead coupling strength. Due to the applied bias voltage spin accumulates on the quantum dot, which for finite charging energy experiences a torque, resulting in spin precession. The latter leads to a non-trivial, interaction-dependent, θ-dependence of the conductance. In particular, we find that the spin-valve effect is reduced for all θ = π. Introduction. -The field of spin-or magnetoelectronics has attracted much interest, for both its beautiful fundamental physics and its potential applications. One famous spin-dependent transport phenomenon is the tunnel magnetoresistance (TMR) in a spin-valve geometry, in which two ferromagnetic metals are separated by an insulating layer serving as a tunnel barrier [1]. The transmission through the barrier decreases as the relative angle θ between the magnetizations of two ferromagnets is increased from 0 to π. Within a single-particle picture the θ-dependent part of the transmission can be shown [2,3] to be proportional to cos θ.

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confidence: 99%

Interaction-Driven Spin Precession in Quantum-Dot Spin Valves

2003

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“…Here n stands for the electron number tunneled through the junctions. Recently, this approach was elegantly applied to quantum transport problems involving such as quantum interference phenomena 29,30 and the quantum shuttle mechanism. 31,32 However, as it starts with the many-particle Schrödinger equation of the entire system, this approach is by far restricted to zero temperature, and also the large bias voltage regime, due to the approximation involved there.…”

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Calculation of the current noise spectrum in mesoscopic transport: A quantum master equation approach

Luo

Yan

2007

Phys. Rev. B

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Based on our recent work on quantum transport ͓X. Q. Li et al., Phys. Rev. B 71, 205304 ͑2005͔͒, we show how an efficient calculation can be performed for the current noise spectrum. Compared to the classical rate equation or the quantum trajectory method, the proposed approach is capable of tackling both the many-body Coulomb interaction and quantum coherence on an equal footing. The practical applications are illustrated by transport through quantum dots. We find that this alternative approach is in a certain sense simpler and more straightforward than the well-known Landauer-Büttiker scattering matrix theory.

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“…where σ jj ′ = n σ n jj ′ , and the shot-noise power spectrum, S(ω), is given by the McDonald formula [12],…”

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Single qubit measurements with an asymmetric single-electron transistor

Gurvitz

Berman

2005

Phys. Rev. B

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We investigate qubit measurements using a single electron transistor (SET). Applying the Schrödinger equation to the entire system we find that an asymmetric SET is considerably more efficient than a symmetric SET. Yet, its efficiency does not reach that of an ideal detector even in the large asymmetry limit. We also compare the SET detector with a point-contact detector. This comparison allows us to illuminate the relation between information gain in the measurement process and the decoherence generated by these measurement devices. : 73.50.-h, 73.23.-b, 03.65.Yz. PACSAn obvious candidate for read-out of the two-state system (qubit) is the single electron transistor (SET) [1,2]. In many respects it is better than the point-contact (PC) detector [1], which has already been used for quantum measurements [3]. It has been shown, however, that the symmetric SET has a rather low sensitivity in its normal working regime [4,5]. Therefore it becomes very important to investigate how to improve the effectiveness of the SET by a proper selection of its parameters.In this Letter we examine qubit measurements using the SET by applying the Schrödinger equation to the entire system of the qubit and detector. In this case, we can unambiguously determine the backaction of the charge fluctuations in the SET on the qubit and the sensitivity of the measurement as a function of the detector parameters. We find that by varying the tunneling barriers of the SET, one can force the latter to operate in a regime where the "active measurement" time is very short. Then the SET behaves as a linear quantum detector even if it is strongly coupled to the measured system. We also demonstrate that in this regime the effectiveness of the SET considerably increases, although it does not reach the ultimate value corresponding to an ideal detector. By varying the set-up parameters of the SET one can investigate decoherence generated by this detector in the operation mode in which the signal decreases to zero. This illuminates the relationship between decoherence and distinguishability in different types of measurements.Consider an electrostatic qubit, represented by an electron in a coupled dot. The qubit is placed in close proximity to the SET, Fig. 1. The latter is shown as a potential well, coupled to two reservoirs at different chemical potentials, µ L,R . We assume that the bias voltage V = µ L − µ R is smaller than the energy spacing of the single particle states of the well. This condition is usually realized in semiconductor quantum dots [6]. Then transport takes place through an individual single particle level, E 0 , in contrast to a metallic SET, in which many conducting levels contribute to transport [7]. One finds that if the electron occupies the upper dot (Figs. 1a,1b) the current flows through the level E 0 of the SET. However, if the electron occupies the lower dot (Figs. 1c,1d), the SET is blocked due to the electronelectron repulsion U . Here we assume that U is large enough so that, where Γ L,R are the partial widths of the leve...

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Interference effects in resonant magnetotransport

Cited by 69 publications

References 26 publications

Interaction-Driven Spin Precession in Quantum-Dot Spin Valves

Interaction-Driven Spin Precession in Quantum-Dot Spin Valves

Calculation of the current noise spectrum in mesoscopic transport: A quantum master equation approach

Single qubit measurements with an asymmetric single-electron transistor

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