Current and power spectrum in a magnetic tunnel device with an atomic-size spacer

Bułka, Bogdan R.

doi:10.1103/physrevb.62.1186

Cited by 125 publications

(142 citation statements)

References 27 publications

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“…It turns out that measurement of the shot noise provides additional information on quantum and Coulomb correlations, which is not accessible in the measurements of average current. [1][2][3][4][5][6][7][8][9][10][11][12][13] The noise measurements are especially important for the physics of mesoscopic structures, where the current fluctuations are expected to be strongly enhanced. 1 The shot noise in mesoscopic conductors was studied theoretically more than two decades ago in the pioneer works of Lesovik 2 and Büttiker et al 3,4 Various aspects of the shot noise and its manifestation in transport characteristics of normal-metallic, semiconducting, and superconducting structures have been reviewed by Blanter and Büttiker.…”

Section: Introductionmentioning

confidence: 99%

Shot noise in magnetic double-barrier tunnel junctions

Szczepański¹,

Dugaev²,

Barnaś³

et al. 2013

Phys. Rev. B

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We calculate shot noise and the corresponding Fano factors in magnetic double-barrier tunnel junctions. Two situations are analyzed: (i) the central metallic layer is nonmagnetic while the external ones are ferromagnetic, and (ii) all of the metallic layers are ferromagnetic. In the latter case, the number of various magnetic configurations of the junctions is larger, which improves the functionality of such devices. The corresponding shot noise and Fano factor are shown to depend on the magnetic configuration of the junctions. The effect of spin relaxation in the central layer is also taken into account. The theoretical results are compared with experimental data on the shot noise in Fe/MgO/Fe/MgO/Fe structures.

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Section: Introductionmentioning

confidence: 99%

Shot noise in magnetic double-barrier tunnel junctions

Szczepański¹,

Dugaev²,

Barnaś³

et al. 2013

Phys. Rev. B

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“…However, several theoretical works on various systems have showed that Coulomb interactions might also lead to a super-Poisson shot noise with a Fano factor F > 1. Examples of such systems are quantum dots that are coupled to ferromagnetic leads [7][8][9][10] , multi-levels quantum dots 11,12 , multidots structures [13][14][15][16][17][18] , and also three terminal quantum dots [19][20][21] . There are also experimental works [22][23][24][25][26] in which a super-Poisson noise was measured in quantum dots, rather than the sub-Poisson noise, which is expected from the single level model of the quantum dots.…”

Section: Introductionmentioning

confidence: 99%

Enhanced shot noise in asymmetric interacting two-level systems

Carmi

Oreg

2012

Phys. Rev. B

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We study a model of two interacting levels that are attached to two electronic leads, where one of the levels is attached very weakly to the leads. We use rate equations to calculate the average current and the noise of electrons transmitted through the two levels. We show that the shot noise is enhanced because of the interactions and that the Fano factor depends on the properties of the couplings between the levels and the leads. We study both sequential tunneling and cotunneling processes and show that there is a range of parameters in which the cotunneling processes affect the noise significantly, even though most of the current is carried by sequential tunneling processes.

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“…[17], and they were found to be negative. The noise of a twoterminal quantum dot with ferromagnetic contacts was studied in the sequential tunneling limit [18,19], and, interestingly, a super-Poissonian Fano factor was found.In this Letter, we consider an interacting threeterminal quantum dot with ferromagnetic leads. The dot is operated as a beam splitter: one contact acts as source and the other two as drains.…”

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confidence: 99%

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confidence: 99%

Positive Cross Correlations in a Three-Terminal Quantum Dot with Ferromagnetic Contacts

2004

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We study current fluctuations in an interacting three-terminal quantum dot with ferromagnetic leads. For appropriately polarized contacts, the transport through the dot is governed by a novel dynamical spin blockade, i.e., a spin-dependent bunching of tunneling events not present in the paramagnetic case. This leads for instance to positive zero-frequency cross-correlations of the currents in the output leads even in the absence of spin accumulation on the dot. We include the influence of spin-flip scattering and identify favorable conditions for the experimental observation of this effect with respect to polarization of the contacts and tunneling rates.PACS numbers: 72.70.+m,72.25.Rb Quantum fluctuations of current in mesoscopic devices have attracted considerable attention in the last years (for reviews, see Refs. [1,2]). It has been shown that the statistics of non-interacting fermions leads to a suppression of noise below the classical Poisson value [3,4,5] and to negative cross-correlations in multi-terminal structures [6]. This was recently confirmed experimentally in a Hanbury Brown-Twiss setup [7]. The question of the sign of cross-correlations has triggered a lot of activity [8], and different mechanisms to obtain positive crosscorrelations in electronic systems have been proposed. Employing a superconductor as a source, positive crosscorrelations have been predicted for several setups [9]. This is because a superconducting source injects highly correlated electron pairs. Screening currents due to longrange Coulomb interactions lead to positive correlations in the finite-frequency voltage noise measured at two capacitors coupled to a coherent conductor [8,10]. Lastly, positive cross-correlations can occur due to the correlated injection of electrons by a voltage probe [12], or due to correlated excitations in a Luttinger liquid [13].Below we will be interested in noise correlations in a quantum dot. This problem was addressed theoretically in the sequential-tunneling limit [14] and in the cotunneling regime [15]. Noise measurements [16] were in agreement with the Coulomb-blockade picture [14]. Crosscorrelations between particle currents in a paramagnetic multi-terminal quantum dot were studied in Ref. [17], and they were found to be negative. The noise of a twoterminal quantum dot with ferromagnetic contacts was studied in the sequential tunneling limit [18,19], and, interestingly, a super-Poissonian Fano factor was found.In this Letter, we consider an interacting threeterminal quantum dot with ferromagnetic leads. The dot is operated as a beam splitter: one contact acts as source and the other two as drains. Our main finding is that sufficiently polarized contacts can lead to a dynamical spin blockade on the dot, i.e., a spin-dependent bunching of tunneling events not present in the paramagnetic case. A striking consequence of this spin blockade is the FIG. 1: Current-voltage characteristic of a quantum dot connected to three ferromagnetic leads i ∈ {1, 2, 3}, with respective polarizations Pi, throu...

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Current and power spectrum in a magnetic tunnel device with an atomic-size spacer

Cited by 125 publications

References 27 publications

Shot noise in magnetic double-barrier tunnel junctions

Shot noise in magnetic double-barrier tunnel junctions

Enhanced shot noise in asymmetric interacting two-level systems

Positive Cross Correlations in a Three-Terminal Quantum Dot with Ferromagnetic Contacts

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