arXiv subjects

Janine Splettstoesser

Publications and source records attributed to Janine Splettstoesser.

At least 91 records · Page 5Linked to original sources

arXiv2012

Interaction-induced charge and spin pumping through a quantum dot at finite bias

We investigate charge and spin transport through an adiabatically driven, strongly interacting quantum dot weakly coupled to two metallic contacts with finite bias voltage. Within a kinetic equation approach, we identify coefficients of response to the time-dependent external driving and relate these to the concepts of charge and spin emissivities previously discussed within the time-dependent scattering matrix approach. Expressed in terms of auxiliary vector fields, the response coefficients allow for a straightforward analysis of recently predicted interaction-induced pumping under periodic modulation of the gate and bias voltage [Phys. Rev. Lett. 104, 226803 (2010)]. We perform a detailed study of this effect and the related adiabatic Coulomb blockade spectroscopy, and, in particular, extend it to spin pumping. Analytic formulas for the pumped charge and spin in the regimes of small and large driving amplitude are provided for arbitrary bias. In the absence of a magnetic field, we obtain a striking, simple relation between the pumped charge at zero bias and at bias equal to the Coulomb charging energy. At finite magnetic field, there is a possibility to have interaction-induced pure spin pumping at this finite bias value, and generally, additional features appear in the pumped charge. For large-amplitude adiabatic driving, the magnitude of both the pumped charge and spin at the various resonances saturate at values which are independent of the specific shape of the pumping cycle. Each of these values provide an independent, quantitative measurement of the junction asymmetry.

cond-mat.mes-hall↗

arXiv2012

Josephson current through interacting double quantum dots with spin-orbit coupling

We study the effect of Rashba spin-orbit interaction on the Josephson current through a double quantum dot in presence of Coulomb repulsion. In particular, we describe the characteristic effects on the magnetic-field induced singlet-triplet transition in the molecular regime. Exploring the whole parameter space, we analyze the effects of the device asymmetry, the orientation of the applied magnetic field with respect to the spin-orbit interaction, and finite temperatures. We find that at finite temperatures the orthogonal component of the spin-orbit interaction exhibits a similar effect as the Coulomb interaction inducing the occurrence of a π-phase at particle-hole symmetry. This provides a new route to the experimental observability of the π-phase in multi-level quantum dots.

cond-mat.mes-hall↗

arXiv2012

Tunneling-induced renormalization in interacting quantum dots

We analyze tunneling-induced quantum fluctuations in a single-level quantum dot with arbitrarily strong onsite Coulomb interaction, generating cotunneling processes and renormalizing system parameters. For a perturbative analysis of these quantum fluctuations, we remove off-shell parts of the Hamiltonian via a canonical transformation. We find that the tunnel couplings for the transitions connecting empty and single occupation and connecting single and double occupation of the dot renormalize with the same magnitude but with opposite signs. This has an important impact on the shape of the renormalization extracted for example from the conductance. Finally, we verify the compatibility of our results with a systematic second-order perturbation expansion of the linear conductance performed within a diagrammatic real-time approach.

cond-mat.mes-hall↗

arXiv2012

Nonlinear adiabatic response of interacting quantum dots

We develop a generic method in Liouville space to describe the dissipative dynamics of coherent interacting quantum dots with adiabatic time dependence beyond linear response. We show how the adiabatic response can be related to effective quantities known from real-time renormalization group methods for stationary quantities. We propose the study of a generalized $RC$-time as a characteristic time scale. We apply the method to the interacting resonant level model and calculate the nonlinear adiabatic charge response to time-dependent gate voltages, tunneling barriers and Coulomb interaction. The generalized $RC$-time is found to acquire a unique form in all cases, in contrast to the capacitance and the charge relaxation resistance. We discuss the observability of the effects in molecular systems and cold atom setups.

cond-mat.mes-hall↗

arXiv2012

Time scales in the dynamics of an interacting quantum dot

We analyze the dynamics of a single-level quantum dot with Coulomb interaction, weakly tunnel coupled to an electronic reservoir, after it has been brought out of equilibrium, e.g. by a step-pulse potential. We investigate the exponential decay towards the equilibrium state, which is governed by three time scales. In addition to the charge and spin relaxation time there is a third time scale which is independent of the level position and the Coulomb interaction. This time scale emerges in the time evolution of physical quantities sensitive to two-particle processes.

cond-mat.mes-hall↗

arXiv2011

Readout of carbon nanotube vibrations based on spin-phonon coupling

We propose a scheme for spin-based detection of the bending motion in suspended carbon-nanotubes, using the curvature-induced spin-orbit interaction. We show that the resulting effective spin-phonon coupling can be used to down-convert the high-frequency vibration-modulated spin-orbit field to spin-flip processes at a much lower frequency. This vibration-induced spin-resonance can be controlled with an axial magnetic field. We propose a Pauli spin blockade readout scheme and predict that the leakage current shows pronounced peaks as a function of the external magnetic field. Whereas the resonant peaks allow for frequency readout, the slightly off-resonant current is sensitive to the vibration amplitude.

cond-mat.mes-hall↗

arXiv2011

Adiabatic pumping in a double-dot Cooper-pair beam splitter

We study adiabatic pumping through a double quantum dot coupled to normal and superconducting leads. For this purpose a perturbation expansion in the tunnel coupling between the dots and the normal leads is performed and processes underlying the pumping current are discussed. Features of crossed Andreev reflection are investigated in the average pumped charge and related to local Andreev reflection in a single quantum dot. In order to distinguish Cooper pair splitting from quasi-particle pumping, we compare the properties of Cooper pair pumping with single-electron pumping in a system with only normal leads. The dependence on the average dot level and the coupling asymmetry turn out to be the main distinguishing features. This is contrasted with the linear conductance for which it is more difficult to distinguish single-particle from Cooper pair transport.

cond-mat.mes-hall↗

arXiv2011

Single-particle interference versus two-particle collisions

We consider a mesoscopic circuit in the quantum Hall effect regime comprising two synchronized single-particle sources emitting particles into a Mach-Zehnder interferometer. While particles from one source can possibly interfere at the interferometer output, particles from the second source are injected directly into one of the interferometer's arms and are used to create tunable and coherent suppression of interference. If particles from the two different sources collide at the interferometer output the magnetic-flux dependence of the charge transferred to one of the output contacts is suppressed. In contrast the interference pattern in the current at a fixed time is preserved and the impact of the second source manifests itself in a time-dependent phase-shift.

cond-mat.mes-hall↗

arXiv2011

Coherence of Single Electron Sources from Mach-Zehnder Interferometry

A new type of electron sources has emerged which permits to inject particles in a controllable manner, one at a time, into an electronic circuit. Such single electron sources make it possible to fully exploit the particles' quantum nature. We determine the single-particle coherence length from the decay of the Aharonov-Bohm oscillations as a function of the imbalance of a Mach-Zehnder interferometer connected to a single electron source. The single-particle coherence length is of particular importance as it is an intrinsic property of the source in contrast to the dephasing length.

cond-mat.mes-hall↗

arXiv2010

Charge and spin pumping through a double quantum dot

We calculate adiabatic charge and spin pumping through a serial double quantum dot with strong Coulomb interaction, coupled to normal metal or ferromagnetic contacts. We use a real-time diagrammatic approach in the regime of weak coupling to the reservoirs. In the case of weak interdot tunnel coupling we investigate the influence of tunnel-induced renormalization effects due to charge fluctuations on the pumped charge and spin. We show that tunneling through thermally excited states can play an important role in the strong interdot coupling regime. In particular, for ferromagnetic contacts, both effects enable the generation of pure spin currents. Furthermore they can lead to an inverted spin-valve effect or even to the inversion of the transport direction going along with a diverging tunneling magneto-resistance.

cond-mat.mes-hall↗

arXiv2010

Charge and spin dynamics in interacting quantum dots

The transient response of a quantum dot with strong Coulomb interaction to a fast change in the gate potential, as well as the stationary ac-response to a slow harmonic variation of the gate potential are computed by means of a real-time diagrammatic expansion in the tunnel-coupling strength. We find that after a fast switching, the relaxation of charge and spin are governed by a single time constant each, which differ from each other due to Coulomb repulsion. We compare the response to a step potential with the $RC$ time extracted from the ac response.

cond-mat.mes-hall↗

arXiv2010

Interaction-induced adiabatic non-linear transport

We calculate the time-dependent non-linear transport current through an interacting quantum dot in the single-electron tunneling regime (SET). We show that an additional dc current is generated by the electron-electron interaction by adiabatic out-of-phase modulation of the gate and bias voltage. This current can arise only when two SET resonance conditions are simultaneously satisfied. We propose an adiabatic transport spectroscopy where lock-in measurement of a "time-averaged stability diagram" probes interactions, tunnel asymmetries and changes in the ground state spin-degeneracy.

cond-mat.mes-hall↗

arXiv2009

Two-particle non-local Aharonov-Bohm effect from two single-particle emitters

We propose a mesoscopic circuit in the quantum Hall effect regime comprising two uncorrelated single-particle sources and two distant Mach-Zehnder interferometers with magnetic fluxes, which allows in a controllable way to produce orbitally entangled electrons. Two-particle correlations appear as a consequence of erasing of which path information due to collisions taking place at distant interferometers and in general at different times. The two-particle correlations manifest themselves as an Aharonov-Bohm effect in noise while the current is insensitive to magnetic fluxes. In an appropriate time-interval the concurrence reaches a maximum and a Bell inequality is violated.

cond-mat.mes-hall↗

arXiv2009

Electron counting with a two-particle emitter

We consider two driven cavities (capacitors) connected in series via an edge state. The cavities are driven such that they emit an electron and a hole in each cycle. Depending on the phase lag the second cavity can effectively absorb the carriers emitted by the first cavity and nullify the total current or the set-up can be made to work as a two-particle emitter. We examine the precision with which the current can be nullified and with which the second cavity effectively counts the particles emitted by the first one. To achieve single-particle detection we examine pulsed cavities.

cond-mat.mes-hall↗

arXiv2009

Adiabatic charge and spin pumping through quantum dots with ferromagnetic leads

We study adiabatic pumping of electrons through quantum dots attached to ferromagnetic leads. Hereby we make use of a real-time diagrammatic technique in the adiabatic limit that takes into account strong Coulomb interaction in the dot. We analyze the degree of spin polarization of electrons pumped from a ferromagnet through the dot to a nonmagnetic lead (N-dot-F) as well as the dependence of the pumped charge on the relative leads' magnetization orientations for a spin-valve (F-dot-F) structure. For the former case, we find that, depending on the relative coupling strength to the leads, spin and charge can, on average, be pumped in opposite directions. For the latter case, we find an angular dependence of the pumped charge, that becomes more and more anharmonic for large spin polarization in the leads.

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arXiv2007

Pumping through a quantum dot in the proximity of a superconductor

We study adiabatic pumping through a quantum dot tunnel-coupled to one normal and one superconducting lead. We generalize a formula which relates the pumped charge through a quantum dot with Coulomb interaction to the instantaneous local Green's function of the dot, to systems containing a superconducting lead. First, we apply this formula to the case of a non-interacting, single-level quantum dot in different temperature regimes and for different parameter choices, and we compare the results with the case of a system comprising only normal leads. Then we study the infinite-U Anderson model with a superconducting lead at zero temperature, and we discuss the effect of the proximity of the superconductor on the pumped charge.

cond-mat.mes-hall↗

arXiv2006

Adiabatic pumping through a quantum dot with coulomb interactions: A perturbation expansion in the tunnel coupling

We present a diagrammatic real-time approach to adiabatic pumping of electrons through interacting quantum dots. Performing a systematic perturbation expansion in the tunnel-coupling strength, we compute the charge pumped through a single-level quantum dot per pumping cycle. The combination of Coulomb interaction and quantum fluctuations, accounted for in contributions of higher order in the tunnel coupling, modifies the pumping characteristics via an interaction-dependent renormalization of the quantum-dot level. The latter is even responsible for the {\em dominant} contribution to the pumped charge when pumping via time-dependent tunnel-coupling strengths.

cond-mat.mes-hall↗

arXiv2005

Adiabatic pumping through interacting quantum dots

We present a general formalism to study adiabatic pumping through interacting quantum dots. We derive a formula that relates the pumped charge to the local, instantaneous Green function of the dot. This formula is then applied to the infinite-U Anderson model both for weak and strong tunnel-coupling strengths.

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