Measurement of the transmission phase through a quantum dot (QD) embedded in an arm of a two-terminal Aharonov-Bohm (AB) interferometer is inhibited by phase symmetry, i.e. the property that the linear response conductance of a two-terminal device is an even function of magnetic field. It is demonstrated that in a setup consisting of an interferometer with a QD in each of its arms, with one of the QDs capacitively coupled to a nearby quantum point contact (QPC), phase symmetry is broken when a finite voltage bias is applied to the QPC. The transmission phase via the uncoupled QD can then be deduced from the amplitude of the odd component of the AB oscillations.
This paper has been retracted. The authors have discovered a possible problem in applications of the dephasing terminal approach to shot noise calculations in interference situations: Eq. (7) correctly re-introduces the anticorrelations between the currents in the two arms, but due to its semiclassical nature probably fails to describe the consequential diminishing of exchange effects at the second beamsplitter.
We theoretically investigate the thermoelectric properties of heat engines based on Mach-Zehnder interferometers. The energy dependence of the transmission amplitudes in such setups arises from a difference in the interferometer arm lengths. Any thermoelectric response is thus of purely quantum mechanical origin. In addition to an experimentally established three-terminal setup, we also consider a two-terminal geometry as well as a four-terminal setup consisting of two interferometers. We find that Mach-Zehnder interferometers can be used as powerful and efficient heat engines which perform we…
Unlike the two-terminal device, in which the time-reversal invariant spin-orbit interaction alone cannot polarize the spins, such a polarization can be generated when electrons from one source reservoir flow into two (or more) separate drain reservoirs. We present analytical solutions for two examples. First, we demonstrate that the electrons transmitted through a "diamond" interferometer into two drains can be simultaneously fully spin-polarized along different tunable directions, even when the two arms of the interferometer are not identical. Second, we show that a single helical molecule at…
We study quantum Hall interferometers in which the interference loop encircles a quantum anti-dot. We base our study on thermodynamic considerations, which we believe reflect the essential aspects of interference transport phenomena. We find that similar to the more conventional Fabry-Perot quantum Hall interferometers, in which the interference loop forms a quantum dot, the anti-dot interferometer is affected by the electro-static Coulomb interaction between the edge modes defining the loop. We show that in the Aharonov-Bohm regime, in which effects of fractional statistics should be visible,…
Phase sensitivity and thermal dephasing in coherent electron transport in quasi one-dimensional (1D) waveguide rings of an asymmetric four-terminal geometry are studied by magnetotransport measurements. We demonstrate the electrostatic control of the phase in Aharonov-Bohm (AB) resistance oscillations and investigate the impact of the measurement circuitry on decoherence. Phase rigidity is broken due to the ring geometry: Orthogonal waveguide cross-junctions and 1D leads minimize reflections and resonances between leads allowing for a continuous electron transmission phase shift. The measureme…
Quantum coherent properties of electrons can be studied in Aharonov-Bohm (AB) interferometers. We investigate both experimentally and theoretically the transmission phase evolution in a four-terminal quasi-one-dimensional AlGaAs/GaAs-based waveguide AB ring. As main control parameter besides the magnetic field, we tune the Fermi wave number along the pathways using a top-gate. Our experimental results and theoretical calculations demonstrate the strong influence of the measurement configuration upon the AB-resistance-oscillation phase in a four-terminal device. While the non-local setup displa…
We use the Aharonov-Bohm effect in a four-terminal ring based on a Ga[Al]As heterostructure for the measurement of the relative transmission phase. In each of the two interfering paths we induce a quantum dot. The number of electrons in the two dots can be controlled independently. The transmission phase is measured as electrons are added to or taken away from the individual quantum dots.
Within the scheme of quantum rate equations, we investigate the spin-resolved transport through a double quantum dot system with four ferromagnetic terminals. It is found that the injection efficiency of spin-polarized electrons can be significantly improved compared with single dot case. When the magnetization in one of four ferromagnetic terminals is antiparallel with the other three, the polarization rate of the current through one dot can be greatly enhanced, accompanied by the drastic decrease of the current polarization rate through the other one. The mechanism is the exchange interactio…
Electronic transport through a triple-quantum-dot ring with three terminals is theoretically studied. By introducing local Rashba spin-orbit interaction on an individual quantum dot, we find that the spin bias in one terminal drives apparent charge currents in the other terminals, accompanied by the similar amplitude and opposite directions of them. Meanwhile, it shows that the characteristics of the spin currents induced by the spin bias are notable. When a magnetic flux is applied through this ring, we see its nontrivial role in the manipulation of the charge and spin currents. With the obta…
In quantum dot circuits, screening electron clouds in strongly-coupled leads will hybridize with the states of the artificial atom. Using a three-terminal geometry, we directly probe the atomic structure of a quantum dot with Kondo coupling. Our measurements reveal that this hybrid system behaves as a non-linear entity with orbital degeneracy. Geometric distortion reduces the symmetry, lowers the energy, and lifts the degeneracy--the Jahn-Teller effect.
Three terminal tunnelling experiments on quantum dots in the Coulomb blockade regime allow a quantitative determination of the coupling strength of individual quantum states to the leads. Exploiting this insight we have observed independent fluctuations of the coupling strengths as a function of electron number and magnetic field due to changes in the shape of the wave function in the dot. Such a detailed understanding and control of the dot-lead coupling can be extended to more complex systems such as coupled dots, and is essential for building functional quantum electronic systems.
A detailed description of the tunneling processes within Aharonov-Bohm (AB) rings containing two-dimensional quantum dots is presented. We show that the electronic propagation through the interferometer is controlled by the spectral properties of the embedded dots and by their coupling with the ring. The transmittance of the interferometer is computed by the Landauer-Büttiker formula. Numerical results are presented for an AB interferometer containing two coupled dots. The charging diagrams for a double-dot interferometer and the Aharonov Bohm oscillations are obtained, in agreement with the r…
We consider two modifications of a recently proposed three-terminal quantum dot heat engine. First, we investigate the necessity of the thermalization assumption, namely that electrons are always thermalized by inelastic processes when traveling across the cavity where the heat is supplied. Second, we analyze various arrangements of tunneling-coupled quantum dots in order to implement a transmission function that is superior to the Lorentzian transmission function of a single quantum dot. We show that the maximum power of the heat engine can be improved by about a factor of two, even for a sma…
We theoretically study electron interference in a ballistic electronic interferometer capacitively coupled to a quantum dot. The visibility of the interference is reduced when the dot has degenerate ground states with different excess charges. The degree of the reduction depends on system parameters such as the strength of the capacitive coupling, and the dependence is analyzed in the regime where the dwell time of electrons in the dot is much longer than the electron flight time through the interferometry region coupled to the dot. The result is consistent with recent experimental data.
We investigate an electronic Mach-Zehnder interferometer with high visibility in the quantum Hall regime. The superposition of the electrostatic potentials from a quantum point contact (QPC) and the residual disorder potential from doping impurities frequently results in the formation of inadvertent quantum dots (QD) in one arm of the interferometer. This gives rise to resonances in the QPC transmission characteristics. While crossing the QD resonance in energy, the interferometer gains a phase shift of $π$ in the interference pattern.
We study an interacting single-level quantum dot weakly coupled to three electrodes. When two electrodes are biased by voltages with opposite polarities, while keeping the third lead (the stem) grounded, the current through the stem is a measure of electron-hole asymmetry of the dot. In this setup we calculate the stem current for both metallic and ferromagnetic (collinearly polarized) leads and discuss how the three-terminal device gives additional information compared to the usual two-terminal setup. We calculate both the sequential and cotunneling contribution for the currents. For the latt…
We consider the time-dependent electron transport through a quantum dot connected to multiple leads in the presence of the additional over-dot (bridge) tunnelling channels by using the evolution operator technique. Each terminal and quantum dot are disturbed by an external oscillating field resulting in a time-dependence of the corresponding energy levels. The final analytical expressions for the currents flowing in the system are given assuming the wide-band limit approximation. We investigate also the transient-current characteristics in the case of the rectangular-pulse modulations imposed …
Coherence in electronic interferometers is typically believed to be restored fully in the limit of small voltages, frequencies and temperatures. However, it is crucial to check this essentially perturbative argument by nonperturbative methods. Here, we use the numerical renormalization group to study ac transport and decoherence in an experimentally realizable model interferometer, a parallel double quantum dot coupled to a phonon mode. The model allows to clearly distinguish renormalization effects from decoherence. We discuss finite frequency transport and confirm the restoration of coherenc…
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 wit…
We study the influence of spin polarization on the degree of coherence of electron transport through interacting quantum dots. To this end, we identify transport regimes in which the degree of coherence can be related to the visibility of the Aharonov-Bohm oscillations in the current through a quantum-dot Aharonov-Bohm interferometer with one normal and one ferromagnetic lead. For these regimes, we calculate the visibility and, thus, the degree of coherence, as a function of the degree of spin polarization of the ferromagnetic lead.
We study electron transport through a closed Aharonov-Bohm interferometer containing two single-level quantum dots. The quantum-dot levels are coupled to each other indirectly via the leads. We find that this coupling yields signatures of an effective flux-dependent level attraction in the linear conductance. Furthermore, we predict a suppression of transport when both levels are close to the Fermi level of the leads. The width of this anomaly is also flux dependent. We identify different regimes in which constructive interference of transmission through identical dots yields a signal that is …
We report measurements of multi-path transport through a triple quantum dot (TQD) in the few-electron regime using a GaAs three-terminal device with a separate lead attached to each dot. When two paths reside inside the transport window and are simultaneously spin-blockaded, the leak currents through both paths are significantly enhanced. We suggest that the transport processes in the two paths cooperate to lift the spin blockade. Fine structures in transport spectra indicate that different kinds of cooperative mechanisms are involved, depending on the details of the three-electron spin states…
We study the quantum interference (QI) effects in three-terminal Andreev interferometers based on polyaromatic hydrocarbons (PAH's) under non-equilibrium conditions. The Andreev interferometer consists of a PAH coupled to two superconducting and one normal conducting terminals. We calculate the current measured in the normal lead as well as the current between the superconducting terminals under non-equilibrium conditions. We show that both the QI arising in the PAH cores and the bias voltage applied to a normal contact have a fundamental effect on the charge distribution associated with the A…
The influence of the inhomogeneous distribution of the magnetic flux on quantum transport through coupled double quantum dots embedded in an Aharonov-Bohm interferometer are investigated. We show that the effective tunnelling coupling between two dots can be tuned by the magnetic flux imbalance threading two AB subrings. Thus the conductance and the local densities of states become periodic functions of the magnetic flux imbalance. Therefore, transport signals can be manipulated by adjusting the magnetic flux imbalance. Thus accurate control of the distribution of the magnetic flux is necessar…
We study electronic transport through an Aharonov-Bohm interferometer with single-level quantum dots embedded in the two arms. The full counting statistics in the shot-noise regime is calculated to first order in the tunnel-coupling strength. The interplay of interference and charging energy in the dots leads to a dynamical channel blockade that is tunable by the magnetic flux penetrating the Aharonov-Bohm ring. We find super-Poissonian behavior with diverging second and higher cumulants when the Aharonov-Bohm flux approaches an integer multiple of the flux quantum.
Mesoscopic solid state Aharonov-Bohm interferometers have been used to measure the "intrinsic" phase, $α_{QD}$, of the resonant quantum transmission amplitude through a quantum dot (QD). For a two-terminal "closed" interferometer, which conserves the electron current, Onsager's relations require that the measured phase shift $β$ only "jumps" between 0 and $π$. Additional terminals open the interferometer but then $β$ depends on the details of the opening. Using a theoretical model, we present quantitative criteria (which can be tested experimentally) for $β$ to be equal to the desired $α_{QD}$…
Electron transport through two parallel quantum dots is a kind of solid-state realization of double-path interference. We demonstrate that the inter-dot Coulomb correlation and quantum coherence would result in strong current fluctuations with a divergent Fano factor at zero frequency. We also provide physical interpretation for this surprising result, which displays its generic feature and allows us to recover this phenomenon in more complicated systems.
We present a statistical readout method for quantum interferences based on time series analysis of consecutive single electron transfers through a double quantum dot Aharonov-Bohm interferometer. Waiting time distributions qualitatively indicate the presence of interferences and provide information on orbital-detuning and coherent interdot-electron transfer. Interdot transfer induced oscillations are Aharonov-Bohm phase sensitive, while those due to level detuning are phase-independent. The signature of the quantum interference in the waiting time distribution is more apparent for weakly coupl…
Dephasing in a ballistic four-terminal Aharonov-Bohm geometry due to charge and voltage fluctuations is investigated. Treating two terminals as voltage probes, we find a strong dependence of the dephasing rate on the probe configuration in agreement with a recent experiment by Kobayashi et al. (J. Phys. Soc. Jpn. 71, 2094 (2002)). Voltage fluctuations in the measurement circuit are shown to be the source of the configuration dependence.
We investigate resonant tunneling through molecular states of coupled double quantum dots embedded in an Aharonov-Bohm (AB) interferometer. The conductance through the system consists of two resonances associated with the bonding and the antibonding quantum states. We predict that the two resonances are composed of a Breit-Wigner resonance and a Fano resonance, those widths and Fano factor depending on the AB phase very sensitively. Further, we point out that the bonding properties, such as the covalent and the ionic bonding, can be identified by the AB oscillations.
We investigate transport in a three-terminal graphene quantum dot. All nine elements of the conductance matrix have been independently measured. In the Coulomb blockade regime accurate measurements of individual conductance resonances reveal slightly different resonance energies depending on which pair of leads is used for probing. Rapid changes in the tunneling coupling between the leads and the dot due to localized states in the constrictions has been excluded by tuning the difference in resonance energies using in-plane gates which couple preferentially to individual constrictions. The inte…
We study the spin-dependent transport of spin-1/2 electrons through an interferometer made of two elongated quantum dots or quantum nanowires, which are subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. Similar to the diamond interferometer proposed in our previous papers [Phys. Rev. B {\bf 84}, 035323 (2011); Phys. Rev. B {\bf 87}, 205438 (2013)], we show that the double-dot interferometer can serve as a perfect spin filter due to a spin interference effect. By appropriately tuning the external electric and magnetic fields which determine the Aharonov…
We theoretically investigate electron transport through an Aharonov-Bohm interferometer containing laterally coupled double quantum dots. We introduce the indirect coupling parameter $α$, which characterizes the strength of the coupling via the reservoirs between two quantum dots. $|α|=1$ indicates the strongest coupling, where only a single mode contributes to the transport in the system. Two conduction modes exist in a system where $|α|\neq 1$. The interference effects such as the Fano resonance and the Aharonov-Bohm oscillation are suppressed as the absolute value of the parameter $α$ decre…
The effect of electron-phonon coupling on transport through a pair of strongly correlated quantum dots embedded in the Aharonov-Bohm ring is considered in the mean field slave boson Kotliar-Ruckenstein approach. It is shown that coupling with phonons opens transport gap in the region of double occupancy. Low-bias conductance and thermopower provide information on electron-phonon coupling strength.
We study the effect of Coulomb interaction on the full counting statistics of an Aharonov-Bohm (AB) interferometer with a single-level quantum dot in one arm in the regime of weak dot-lead and lead-lead tunnel couplings. In the absence of Coulomb interaction, the interference processes are of nonresonant nature with an even AB flux dependence and obey bidirectional Poissonian statistics. For large charging energy, the statistic of these processes changes. In addition, processes of resonant nature with an odd flux dependence appear. In the limit of strongly asymmetric tunnel couplings from the …
Finite bias spectroscopy measurements of a three-terminal graphene quantum dot are presented. Numerous lines of enhanced differential conductance are observed outside the Coulomb diamonds. In the single-level transport regime such lines are often associated with transport through excited states. Here the system is in the multi-level transport regime. We argue that the lines are most likely a result of strong coupling to only a few of the excited states available in the bias window. We also discuss the option that fluctuations of the density of states in the leads are fully or partly responsibl…
We investigate the Josephson effect in one triple-terminal junction with embedded parallel-coupled double quantum dots. It is found that the inter-superconductor supercurrent has opportunities to oscillate in $4π$ period, with the adjustment of the phase differences among the superconductors. What is notable is that such a result is robust and independent of fermion parities, intradot Coulomb strength, and the dot-superconductor coupling manner. By introducing the concept of spinful many-particle Majorana modes, we present the analytical definition of the Majorana operator via superposing elec…
We study electron transport through a triple quantum dot in ring configuration at finite bias. In particular, we analyze the influence of a gate voltage that detunes one of the dots, such that one branch of the interferometer becomes off-resonant. It turns out that then interference effects fade away, i.e., the current becomes independent of a penetrating flux and the detuning. The noise properties which are characterized by the full-counting statistics, however, are governed by bunching effects that may be tuned by the gate voltage. Analytical results for limiting cases support this picture. …
We investigate the interplay between long-range and direct photon-assisted transport in a triple quantum dot chain where local ac voltages are applied to the outer dots. We propose the phase difference between the two ac voltages as an external parameter, which can be easily tuned to manipulate the current characteristics. For gate voltages in phase opposition we find quantum destructive interferences analogous to the interferences in closed-loop undriven triple dots. As the voltages oscillate in phase, interferences between multiple paths give rise to dark states. Those totally cancel the cur…
In this paper, we investigate transient quantum transport in a nanoscale Aharonov-Bohm (AB) interferometer consisting of a laterally coupled double quantum dot (DQD) coupled to the source and drain electrodes. The transient linear conductance is derived at finite temperature of the leads, and is divided into three terms contributed from different transport channels. By observing the transient linear conductance and time evolution of the elements of the reduced density matrix of the DQD system, we show the nature of how Fano resonance is built up in the time domain.
We report experiments on the interference through spin states of electrons in a quantum dot (QD) embedded in an Aharonov-Bohm (AB) interferometer. We have picked up a spin-pair state, for which the environmental conditions are ideally similar and have traced the AB amplitude in the range of the gate voltage that covers the pair. The behavior of the asymmetry in the amplitude around the two Coulomb peaks agrees with the theoretical prediction that relates a spin-flip process in a QD to the quantum dephasing of electrons. These results consist evidence of "partial coherence" due to an entangleme…
In this work, we show that in a four-quantum-dot ring, via introducing a local Rashba spin-orbit interaction the spin bias in the transverse terminals can be detected by observing the charge currents in the longitudinal probes. It is found that due to the Rashba interaction, the quantum interference in this system becomes spin-dependent and the opposite-spin currents induced by the spin bias can present different magnitudes, so charge currents emerge. Besides, the charge currents rely on both the magnitude and spin polarization direction of the spin bias. It is believed that this method provid…
We have studied the electron transport through a quantum dot coupled to three leads in the presence of external microwave fields supplied to different parts of the considered mesoscopic system. Additionally, we introduced a possible nonresonant tunneling channels between leads. The quantum dot charge and currents were determined in terms of the appropriate evolution operator matrix elements and under the wide band limit the analytical formulas for time-averaged currents and differential conductance were obtained. We have also examined the response of the considered system on the rectangular-pu…
We study the Fano effect and the visibility of the Aharonov-Bohm oscillations for a mesoscopic interferometer with an embedded quantum dot in the presence of a nearby second dot. When the electron-electron interaction between the two dots is considered the nearby dot acts as a charge detector. We compute the currents through the interferometer and detector within the Keldysh formalism and the self-energy of the non-equilibrium Green functions is found up to the second order in the interaction strength. The current formula contains a correction to the Landauer-B\"{uttiker} formula. Its contribu…
Real-time nonequilibrium quantum dynamics of electrons in double-dot Aharonov-Bohm (AB) interferometers is studied using an exact solution of the master equation. The building of the coherence between the two electronic paths shows up via the time-dependent amplitude of the AB oscillations in the transient transport current, and can be enhanced by varying the applied bias on the leads, the on-site energy difference between the dots and the asymmetry of the coupling of the dots to the leads. The transient oscillations of the transport current do not obey phase rigidity. The circulating current …
We propose a scheme of multilayer thermoelectric engine where {\em one} electric current is coupled to {\em two} temperature gradients in three-terminal geometry. This is realized by resonant tunneling through quantum dots embedded in two thermal and electrical resisting polymer matrix layers between highly conducting semiconductor layers. There are two thermoelectric effects, one of which is pertaining to inelastic transport processes (if energies of quantum dots in the two layers are different) while the other exists also for elastic transport processes. {These two correspond to the transver…
Detecting the transmission phase of a quantum dot via interferometry can reveal the symmetry of the orbitals and details of electron transport. Crucially, interferometry will enable the read-out of topological qubits based on one-dimensional nanowires. However, measuring the transmission phase of a quantum dot in a nanowire has not yet been established. Here, we exploit recent breakthroughs in the growth of one-dimensional networks and demonstrate interferometric read-out in a nanowire-based architecture. In our two-path interferometer, we define a quantum dot in one branch and use the other p…
Rectification of thermal fluctuations in mesoscopic conductors is the key idea of today's attempts to build nanoscale thermoelectric energy harvesters in order to convert heat into a useful electric power. So far, most concepts make use of the Seebeck effect in a two-terminal geometry where heat and charge are both carried by the same particles. Here, we experimentally demonstrate the working principle of a new kind of energy harvester, proposed recently using two capacitively coupled quantum dots. We show that due to its novel three-terminal design which spatially separates the heat reservoir…
We investigate decoherence in a triple quantum dot in ring configuration in which one dot is coupled to a damped phonon mode, while the other two dots are connected to source and drain, respectively. In the absence of decoherence, single electron transport may get blocked by an electron falling into a superposition decoupled from the drain and known as dark state. Phonon-mediated decoherence affects this superposition and leads to a finite current. We study the current and its shot noise numerically within a master equation approach for the electrons and the dissipative phonon mode. A polaron …
We examine the shot noise spectrum properties of coherent resonant tunneling in coupled quantum dots in both series and parallel arrangements by means of quantum rate equations and MacDonald's formula. Our results show that, for a series-CQD with a relatively high dot-dot hopping $Ω$, $Ω/Γ\gtrsim 1$ ($Γ$ denotes the dot-lead tunnel-coupling strength), the noise spectrum exhibits a dip at the Rabi frequency, $2Ω$, in the case of noninteracting electrons, but the dip is supplanted by a peak in the case of strong Coulomb repulsion; furthermore, it becomes a dip again for a completely symmetric pa…
We study three-terminal linear and nonlinear transport through an Aharonov-Bohm interferometer containing a double quantum dot using the nonequilibrium Green's function method. Under the condition that one of the three terminals is a voltage probe, we show that the linear conductance is symmetric with respect to the magnetic field (phase symmetry). However, in the nonlinear transport regime, the phase symmetry is broken. Unlike two-terminal transport, the phase symmetry is broken even in noninteracting electron systems. Based on the lowest-order nonlinear conductance coefficient with respect t…
We examine transport and microwave properties of two coupled quantum dots taken in parallel connection to the common left lead and connected to separate leads at their right side. In addition, the area between the left lead and the double-dot structure is threaded by Aharonov-Bohm magnetic flux. We determine the energies and populations of double-dot levels on the microscopic basis taking into account the interdot Coulomb interaction and show that at large lead-to-lead bias the population inversion can be achieved. For the case of strong Coulomb repulsion, this inversion leads to level crossin…
Measurements of elastic and inelastic cotunneling currents are presented on a two-terminal Aharonov--Bohm interferometer with a Coulomb blockaded quantum dot embedded in each arm. Coherent current contributions, even in magnetic field, are found in the nonlinear regime of inelastic cotunneling at finite bias voltage. The phase of the Aharonov--Bohm oscillations in the current exhibits phase jumps of $π$ at the onsets of inelastic processes. We suggest that additional coherent elastic processes occur via the excited state. Our measurement technique allows the detection of such processes on a ba…
The ``Which Path?'' interferometer consists of an Aharonov-Bohm ring with a quantum dot (QD) built in one of its arms, and an additional quantum point contact (QPC) located close to the QD. The transmission coefficient of the QPC depends on the charge state of the QD. Hence the point contact causes controllable dephasing of transport through the QD, and acts as a measurement device for which path an electron takes through the ring. We calculate the suppression of the Aharonov-Bohm oscillations which is caused both by dephasing and by the orthogonality catastrophe, i.e., respectively, by real a…
Nanodevices consisting of a quantum dot tunnel coupled to one superconducting and two normal electrodes may serve as a source of entangled electrons. As a result of crossed Andreev reflection the Cooper pair of s-wave character may be split into two electrons and each of them goes into a distinct normal electrode, preserving entanglement. Efficiency of the process depends on the specific system and is tunable by electric means. Our calculations show that in the studied device this efficiency may attain values as large as $80 \%$.
We prepare a triple quantum dot with a separate contact lead to each dot to study Pauli spin blockade in the tunnel-coupled three dots in a row. We measure the tunneling current flowing between the center dot and either the left or right dot with the left and right leads as a common source and the center lead as a drain. In the biased stability diagram, we establish Pauli spin blockade in the respective neighboring dots, with features similarly obtained in double quantum dot systems. We further realize Pauli spin blockade with two different conditions by tuning the inter-dot coupling gates: st…
We study theoretically the transmission through a quantum dot molecule embedded in the arms of an Aharonov-Bohm four quantum dot ring threaded by a magnetic flux. The tunable molecular coupling provides a transmission pathway between the interferometer arms in addition to those along the arms. From a decomposition of the transmission in terms of contributions from paths, we show that antiresonances in the transmission arise from the interference of the self-energy along different paths and that application of a magnetic flux can produce the suppression of such antiresonances. The occurrence of…
By applying a local Rashba spin-orbit interaction on an individual quantum dot of a four-terminal four-quantum-dot ring and introducing a finite bias between the longitudinal terminals, we theoretically investigate the charge and spin currents in the transverse terminals. It is found that when the quantum dot levels are separate from the chemical potentials of the transverse terminals, notable pure spin currents appear in the transverse terminals with the same amplitude and opposite polarization directions. Besides, the polarization directions of such pure spin currents can be inverted by alte…
