Spin Switching via Quantum Dot Spin Valves

Gergs, Niklas M.; Bender, Scott; Duine, RA Rembert; Schuricht, Dirk

doi:10.1103/physrevlett.120.017701

Cited by 21 publications

(11 citation statements)

References 40 publications

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“…To calculate the charge and heat currents flowing through the system we use the Real Time Diagrammatic (RTD) theory, [50][51][52][53][54][55][56] in which generalized Master equations are set up by expanding the Liouville-von Neumann equation in H T . The stationary state reduced density operator of the QD, ρ D , is obtained by integrating out the reservoirs and solving the resulting Master equations while imposing probability normalization:…”

Section: Transport Theorymentioning

confidence: 99%

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Optimal power and efficiency of single quantum dot heat engines: Theory and experiment

et al. 2019

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Quantum dots (QDs) can serve as near perfect energy filters and are therefore of significant interest for the study of thermoelectric energy conversion close to thermodynamic efficiency limits. Indeed, recent experiments in [Nat. Nano. 13, 920 (2018)] realized a QD heat engine with performance near these limits and in excellent agreement with theoretical predictions. However, these experiments also highlighted a need for more theory to help guide and understand the practical optimization of QD heat engines, in particular regarding the role of tunnel couplings on the performance at maximum power and efficiency for QDs that couple seemingly weakly to electronic reservoirs. Furthermore, these experiments also highlighted the critical role of the external load when optimizing the performance of a QD heat engine in practice. To provide further insight into the operation of these engines we use the Anderson impurity model together with a Master equation approach to perform power and efficiency calculations up to co-tunneling order. This is combined with additional thermoelectric experiments on a QD embedded in a nanowire where the power is measured using two methods. We use the measurements to present an experimental procedure for efficiently finding the external load RP which should be connected to the engine to optimize power output. Our theoretical estimates of RP show a good agreement with the experimental results, and we show that second order tunneling processes and non-linear effects have little impact close to maximum power, allowing us to derive a simple analytic expression for RP . In contrast, we find that the electron contribution to the thermoelectric efficiency is significantly reduced by second order tunneling processes, even for rather weak tunnel couplings.I.

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Section: Transport Theorymentioning

confidence: 99%

“…Explicit expressions for setting up the kernels W r to order Γ and Γ 2 are given in the supplemental material of Ref. 56. The currents flowing through the system can be calculated once ρ D is obtained.…”

Section: Transport Theorymentioning

confidence: 99%

Optimal power and efficiency of single quantum dot heat engines: Theory and experiment

et al. 2019

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“…The latter originate from the coherent superposition of the degenerate states which arise in this coherent-sequential-tunneling (CST) regime and are modulated by the external parameters like the bias and gate voltage. For a spinful level coupled to noncollinearly polarized ferromagnetic leads (a QD spin valve), interference between the degenerate spin states induces spin accumulation, precession, and relaxation, with a resulting nonequilibrium spin polarization of the dot [2][3][4][5][6][7][8][9] and spin torque on the leads [10].…”

Section: Introductionmentioning

confidence: 99%

Pseudospin resonances reveal synthetic spin-orbit interaction

Rohrmeier

Donarini

2021

Phys. Rev. B

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We investigate a spinful double quantum dot coupled to leads in a pseudospin valve configuration. The interplay of interaction and interference produces, in the stability diagram, a rich variety of current resonances modulated by the system parameters. In the presence of ferromagnetic leads and pseudospin anisotropy, those resonances split, turn into dips, and acquire a Fano shape, thus revealing a synthetic spin-orbit interaction induced on the double quantum dot. A set of rate equations derived for a minimal model captures those features. The model accurately matches the numerical results obtained for the full system in the framework of a generalized master equation and calculated within the next to leading order approximation.

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“…By spin-dependent charge fluctuations, the orbital level of the dot becomes spin-split and consequently mainly the electrons with favorable spin orientation are transferred through the system. Moreover, it turns out that the exchange field results in high spin polarization of the local density of states, which is responsible for controllable spin rectification of the current [18] From a theoretical point of view, the transport properties of quantum dot spin valves, consisting of single dots coupled to ferromagnetic leads, have already been a subject of extensive studies, both in the weak [3,4,8,[22][23][24] and in the strong coupling regime [15,[19][20][21]25]. Moreover, more complex structures involving double quantum dots with ferromagnetic leads have also been explored [26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Large voltage-tunable spin valve based on a double quantum dot

Tulewicz,

Wrzesniewski,

Csonka

et al. 2021

Preprint

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We study the spin-dependent transport properties of a spin valve based on a double quantum dot. Each quantum dot is assumed to be strongly coupled to its own ferromagnetic lead, while the coupling between the dots is relatively weak. The current flowing through the system is determined within the perturbation theory in the hopping between the dots, whereas the spectrum of a quantum dot-ferromagnetic lead subsystem is determined by means of the numerical renormalization group method. The spin-dependent charge fluctuations between ferromagnets and quantum dots generate an effective exchange field, which splits the double dot levels. Such field can be controlled, separately for each quantum dot, by the gate voltages or by changing the magnetic configuration of external leads. We demonstrate that the considered double quantum dot spin valve setup exhibits enhanced magnetoresistive properties, including both normal and inverse tunnel magnetoresistance. We also show that this system allows for the generation of highly spin-polarized currents, which can be controlled by purely electrical means. The considered double quantum dot with ferromagnetic contacts can thus serve as an efficient voltage-tunable spin valve characterized by high output parameters.

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Spin Switching via Quantum Dot Spin Valves

Cited by 21 publications

References 40 publications

Optimal power and efficiency of single quantum dot heat engines: Theory and experiment

Optimal power and efficiency of single quantum dot heat engines: Theory and experiment

Pseudospin resonances reveal synthetic spin-orbit interaction

Large voltage-tunable spin valve based on a double quantum dot

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