Spin Blockades in Linear and Nonlinear Transport through Quantum Dots

Weinmann, Dietmar; Häusler, Wolfgang; Krämer, B.

doi:10.1103/physrevlett.74.984

Cited by 252 publications

(223 citation statements)

References 18 publications

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“…28,29 That the spin has not changed by more than ±1/2 is consistent with the absense of spin blockade. 27 Note that instead of the usual enhancement of the Kondo peak upon approaching the charge degeneracy point a slight depression is observed near V g = 2.0 V in Fig. 2 In the leftmost diamond, yet another electron has been removed, and the molecule has acquired one more spin, (S 3 ).…”

Section: From the Clear Observation Of A Zeeman Effect [See Figs 2(dmentioning

confidence: 99%

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Manipulation of organic polyradicals in a single-molecule transistor

et al. 2012

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Inspired by cotunneling spectroscopy of spin-states in a single OPE5-based molecule, we investigate the prospects for electric control of magnetism in purely organic molecules contacted in a three-terminal geometry. Using the gate electrode, the molecule is reversibly switched between three different redox states, with magnetic spectra revealing both ferromagnetic and antiferromagnetic exchange couplings on the molecule. These observations are shown to be captured by an effective low-energy Heisenberg model, which we substantiate microscopically by a simple valence bond description of the molecule. These preliminary findings suggest an interesting route towards functionalized all-organic molecular magnetism.

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Section: From the Clear Observation Of A Zeeman Effect [See Figs 2(dmentioning

confidence: 99%

“…Since changing V g across a charge degeneracy point adds one electron at the time and we observe no spin blockade, 27 the most general effective three-spin model is the one sketched in Fig. 1(b), described by the Hamiltonian…”

Section: From the Clear Observation Of A Zeeman Effect [See Figs 2(dmentioning

confidence: 99%

Manipulation of organic polyradicals in a single-molecule transistor

et al. 2012

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“…The importance of finite range interactions has been found already in zero dimensional systems, quantum dots, where 'crystallisation' of the charge density distribution can occur leading to qualitative changes in the low energy excitation spectra [13][14][15] as compared to what is expected for a contact interaction 16 .…”

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confidence: 99%

Non-linear current through a barrier in 1D wires with finite-range interactions

Steiner

Häusler

1997

Solid State Communications

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The transport properties of a tunnel barrier in a one-dimensional wire are investigated at finite voltages and temperatures. We generalize the Luttinger model to account for finite ranges of the interaction. This leads to deviations from the power law behaviour first derived by Kane and Fisher 1 . At high energies the influence of the interaction disappears and the Coulomb blockade is suppressed. The crossover in the voltage or in the temperature dependence can provide a direct measure for the range of the interaction.Keywords : electron-electron interactions, electronic transport, tunnelling.Since the discovery of the vanishing transmittivity of a tunnel barrier in a one-dimensional (1D) wire due to the repulsive electron-electron interaction 1 new interest has emerged in the transport properties of 1D electron systems 2-10 . Indeed, the influence of the electron correlations shows up strikingly in non-linear current voltage relations which are investigated experimentally in narrow, semiconducting wires 11 . Local interactions, v(x−x ′ ) = v 0 δ(x−x ′ ) are described within the Luttinger model for which the power-law 1-5has been predicted for the current-voltage relation through a tunnel barrier with tunnel resistance R T , at zero temperature T = 0 . A similar behaviour has been found for the linear conductance ∼ T 2/g−2 as a function of temperature 1,2,5 . The exponent depends on

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“…This analogy manifests itself in an isospin blockade of transport through the double dot system [5,6,7]. Furthermore, the localization provides an effective two-level system which may be useful as a field-tunable charge qubit.…”

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confidence: 99%

“…In special cases a transition is forbidden since it violates conservation laws. A well-known example is the spin-blockade that occurs if the spins of the two states differ by more than ∆S = ± 1 2 [5]. For general cases the effect of the structure of the wavefunctions enters the transition rates through the spectral weights [9] that determine the probability for an electron entering a N -electron state of the DQD to cause a transition to a N + 1-electron state of the DQD.…”

mentioning

confidence: 99%

Isospin blockade in transport through vertical double quantum dots

Wünsch¹,

Jacob²,

Pfannkuche³

2005

Physica E: Low-dimensional Systems and Nanostructures

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We study the spectrum and the transport properties of two identical, vertically coupled quantum dots in a perpendicular magnetic field. We find correlation-induced energy crossings in a magnetic field sweep between states differing only in the vertical degree of freedom. Considering the influence of a slight asymmetry between the dots caused by the applied source-drain voltage in vertical transport experiments these crossings convert to anticrossings accompanied by the build-up of charge polarization which is tunable by the perpendicular magnetic field. The polarization strongly affects the vertical transport through the double quantum dot and is manifest in an isospin blockade and the appearance of negative differential conductances in the magnetic field range where the charge localization occurs. Double quantum dots have recently attracted much interest as possible implementations of qubits and as model systems to study the few-particle physics of molecular binding [1,2,3]. In vertically coupled double quantum dots (DQD) the molecular binding for a single electron is determined by the vertical degree of freedom, while the lateral degree of freedom reflects the physics of the single dots or quasiatoms building up the molecule. In this paper we describe level crossings between few-particle states differing only in parity along the vertical direction. These crossings are based on Coulomb correlations between the electrons and may lead to strong charge polarization, which is tunable by an external perpendicular magnetic field [4]. Thus, these crossings mark changes of the molecular binding which originate from many-body effects.1 Corresponding author. E-mail: bwunsch@physnet.unihamburg.deBesides its importance for quantum dot physics, the effect illuminates the analogy between real spin and isospin, the latter of which describes the vertical degree of freedom [1]. This analogy manifests itself in an isospin blockade of transport through the double dot system [5,6,7]. Furthermore, the localization provides an effective two-level system which may be useful as a field-tunable charge qubit.We model the DQD in vertical direction by two parallel layers separated by a distance d. In lateral direction the electrons are confined by a rotationallysymmetric parabolic potential of strength ω0. Therefore, the vertical degree of freedom is reduced to an additional spin-like degree of freedom, the isospin [1]. In analogy to the real spin one can define a spin algebra for the isospin, where the z-component Iz specifies the vertical degree of freedom. An electron with Iz = +1/2 (Iz = −1/2) is situated in the upper (lower) dot. We

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Spin Blockades in Linear and Nonlinear Transport through Quantum Dots

Cited by 252 publications

References 18 publications

Manipulation of organic polyradicals in a single-molecule transistor

Manipulation of organic polyradicals in a single-molecule transistor

Non-linear current through a barrier in 1D wires with finite-range interactions

Isospin blockade in transport through vertical double quantum dots

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