Current correlations in an interacting Cooper-pair beam splitter

Rech, Jérôme; Chevallier, Denis; Jonckheere, Thibaut; Martin, Thierry

doi:10.1103/physrevb.85.035419

Cited by 48 publications

(47 citation statements)

References 31 publications

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“…Let us note that the crucial role of interactions on the currents and current cross-correlations has also been found in the work on the hybrid devices with two quantum dots 75 . Electron interactions which are expected to destroy quantum correlations in an electron gas in fact induce them in a suitably tuned nanodevices.…”

Section: Discussionmentioning

confidence: 63%

Interplay between direct and crossed Andreev reflections in hybrid nanostructures

et al. 2013

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The interplay between various many body effects in a quantum dot attached to two normal and one superconducting lead is considered in the limit of large superconducting gap. By the proximity effect the superconducting lead induces pairing correlations on the quantum dot. In the subgap region one observes the anomalous tunneling via direct and crossed Andreev scattering, whereas the usual single particle electronic transfer is suppressed. The interactions of electrons on the dot leading to such phenomena as the Coulomb blockade and the Kondo effect severely modify the currents flowing in the system. In particular: (i) they prevent the existence of the negative differential conductance observed for non-interacting quantum dot over the whole range of voltages, (ii) affect the distribution of the currents as function of the applied voltage and (iii) lead to the appearance of additional low bias feature due to the formation of the Abrikosov-Suhl resonance. The non-local correlations in the Coulomb blockade regime are most pronounced for the particle-hole symmetric dot and thus can be easily tuned by means of gate voltage. They are observed even in the Kondo regime and dominate the behavior close to the Abrikosov-Suhl resonance showing convincingly that Kondo correlations do not destroy subtle entanglement between electrons.

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Section: Discussionmentioning

confidence: 63%

Interplay between direct and crossed Andreev reflections in hybrid nanostructures

et al. 2013

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“…To account for the observed interference patterns also requires us to go beyond earlier coherent two-dot models [10,25,26], where the QDs are coupled by direct tunneling. Here, we introduce a three-site model, shown schematically in Fig.…”

mentioning

confidence: 99%

Magnetic Field Tuning and Quantum Interference in a Cooper Pair Splitter

et al. 2015

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Cooper pair splitting (CPS) is a process in which the electrons of the naturally occurring spin-singlet pairs in a superconductor are spatially separated using two quantum dots. Here, we investigate the evolution of the conductance correlations in an InAs CPS device in the presence of an external magnetic field. In our experiments the gate dependence of the signal that depends on both quantum dots continuously evolves from a slightly asymmetric Lorentzian to a strongly asymmetric Fano-type resonance with increasing field. These experiments can be understood in a simple three-site model, which shows that the nonlocal CPS leads to symmetric line shapes, while the local transport processes can exhibit an asymmetric shape due to quantum interference. These findings demonstrate that the electrons from a Cooper pair splitter can propagate coherently after their emission from the superconductor and how a magnetic field can be used to optimize the performance of a CPS device. In addition, the model calculations suggest that the estimate of the CPS efficiency in the experiments is a lower bound for the actual efficiency. In the Cooper pair splitting (CPS) process the electrons of the Cooper pairs in a superconductor are separated spatially using two quantum dots (QDs) coupled in parallel to a central superconductor contact (S) in a three-terminal geometry [1-3], see Fig. 1(a). The Coulomb repulsion on the QDs and the quasiparticle energy gap of the superconductor enforce the electrons to separate into different normal metal electrodes (N1 and N2). Since Cooper pairs are spin-singlet states, such devices could serve as a source of nonlocal spin entangled electron pairs. Similar geometries are also relevant in the search for Majorana bound states [4] in local S-N junction experiments and in threeterminal devices, where an increase in CPS efficiency might serve as a signature of the elusive exotic states [5].In a series of recent experiments on semiconducting nanowires (NWs) [6][7][8][9], carbon nanotubes [10-12], and graphene [13], CPS was demonstrated by positive conductance correlations between the currents from S into N1 and N2. In these experiments, external magnetic fields were solely used to suppress the superconductivity for control experiments, but not as a parameter to tune CPS. In addition, most experiments were interpreted in terms of an incoherent picture with independent transport mechanisms, only coupled by the QD dynamics [9,11].Here, we report experiments in a NW-based Cooper pair splitter with a Nb superconducting electrode. The large critical magnetic field of Nb allows us to explore CPS up to ∼1 T. We find that the conductance correlations can not only manifest as symmetric peaks and dips in the gate dependence, but also as strongly asymmetric shapes reminiscent of Fano resonances. We interpret the experimental results in a minimal model that incorporates the superconducting proximity effect, the tunnel coupling between the QDs, and quantum interference [see Fig. 1(b)]. Interference results in asymmetric...

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“…Next we get the full Green function of the system which allows us to derive a general formula for the current and the higher cumulants. Importantly, this model is quite general and could be used to take into account, for instance, the Coulomb interaction in the nanowire [36,37].…”

Section: Introductionmentioning

confidence: 99%

Tomography of Majorana fermions with STM tips

Chevallier

Klinovaja

2016

Phys. Rev. B

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We investigate numerically the possibility to detect the spatial profile of Majorana fermions (MFs) by using STM tips that are made of either normal or superconducting material. In both cases, we are able to resolve the localization length and the oscillation period of the MF wave function. We show that the tunneling between the substrate and the tip, necessary to get the information on the wave-function oscillations, has to be weaker in the case of a superconducting probe. In the strong tunneling regime, the differential conductance saturates making it more difficult to observe the exponential decay of MFs. The temperature broadening of the profile is strongly suppressed in the case of the superconducting tip resulting, generally, in better resolution.

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Current correlations in an interacting Cooper-pair beam splitter

Cited by 48 publications

References 31 publications

Interplay between direct and crossed Andreev reflections in hybrid nanostructures

Interplay between direct and crossed Andreev reflections in hybrid nanostructures

Magnetic Field Tuning and Quantum Interference in a Cooper Pair Splitter

Tomography of Majorana fermions with STM tips

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