Photon-assisted Andreev tunneling through a mesoscopic hybrid system

Sun, Qing-Feng; Wang, Jian; Lin, Tie

doi:10.1103/physrevb.59.13126

Cited by 89 publications

(94 citation statements)

References 50 publications

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“…[10][11][12][13][14][15] In this system, the Andreev reflection (the proximity effect) at the QD-S interface induces the superconducting correlation in the QD, which has a tendency to form the spin-singlet state. On the other hand, for large Coulomb interactions, the Kondo effect is enhanced and therefore the Kondo spin-singlet state is stabilized between the spin moment in the QD and the conduction electrons in the leads.…”

Section: Introductionmentioning

confidence: 99%

Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads

2007

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We study transport through a quantum dot coupled to normal and superconducting leads using the numerical renormalization group method. We show that the low-energy properties of the system are described by the local Fermi liquid theory despite of the superconducting correlations penetrated into the dot due to a proximity effect. We calculate the linear conductance due to the Andreev reflection in the presence of the Coulomb interaction. It is demonstrated that the maximum structure appearing in the conductance clearly characterizes a crossover between two distinct spin-singlet ground states, i.e. the superconducting singlet state and the Kondo singlet state. It is further elucidated that the gate-voltage dependence of the conductance shows different behavior in the superconducting singlet region from that in the Kondo singlet region.

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Section: Introductionmentioning

confidence: 99%

Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads

2007

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“…However, quantum dot circuits with superconducting reservoirs have been coupled neither to microwave cavities nor to a direct ac excitation, so far. Despite this lack of experiments, photon-assisted tunneling between a dot and a superconductor has created theoretical interest for more than 15 years [50][51][52][53][54][55][56][57][58][59]. The coupling between superconductor-quantum dot hybrid circuits and microwave cavities has also been studied in recent theoretical works [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Cavity Photons as a Probe for Charge Relaxation Resistance and Photon Emission in a Quantum Dot Coupled to Normal and Superconducting Continua

et al. 2016

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Microwave cavities have been widely used to investigate the behavior of closed few-level systems. Here, we show that they also represent a powerful probe for the dynamics of charge transfer between a discrete electronic level and fermionic continua. We have combined experiment and theory for a carbon nanotube quantum dot coupled to normal metal and superconducting contacts. In equilibrium conditions, where our device behaves as an effective quantum dot-normal metal junction, we approach a universal photon dissipation regime governed by a quantum charge relaxation effect. We observe how photon dissipation is modified when the dot admittance turns from capacitive to inductive. When the fermionic reservoirs are voltage biased, the dot can even cause photon emission due to inelastic tunneling to/from a BardeenCooper-Schrieffer peak in the density of states of the superconducting contact. We can model these numerous effects quantitatively in terms of the charge susceptibility of the quantum dot circuit. This validates an approach that could be used to study a wide class of mesoscopic QED devices.

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“…The latter was used to explain the resonance peaks experimentally observed in vibrating Nb nanowires [136,137]. On the contrary, the hybrid case of a normal-dotsuperconductor (N-QD-S) coupled to the bosonic modes-as photons [138,139] or phonons [140][141][142]-has been less studied in the literature and is theoretically unexplored for the nonequilibrium regime of the oscillator. In this system, one expects that the role of the superconducting lead is unessential for ω ( the superconducting gap) as the vibrational frequency ω sets the energy scale of the inelastic tunneling of electrons.…”

Section: Introductionmentioning

confidence: 99%

Charge-vibration interaction effects in normal-superconductor quantum dots

2017

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We study the quantum transport and the nonequilibrium vibrational states of a quantum dot embedded between a normal-conducting and a superconducting lead with the charge on the quantum dot linearly coupled to a harmonic oscillator of frequency ω. To the leading order in the charge-vibration interaction, we calculate the current and the nonequilibrium phonon occupation by the Keldsyh Green's function technique. We analyze the inelastic, vibration-assisted tunneling processes in the regime ω < , with the superconducting energy gap , and for sharp resonant transmission through the dot. When the energy ε 0 of the dot's level is close to the Fermi energy μ, i.e., |ε 0 − μ| , inelastic vibration-assisted Andreev reflections dominate up to voltage eV . The inelastic quasiparticle tunneling becomes the leading process when the dot's level is close to the superconducting gap |ε 0 − μ| ∼ ± ω. In both cases, the inelastic tunneling processes appear as sharp and prominent peaks-not broadened by temperature-in the current-voltage characteristic and pave the way for inelastic spectroscopy of vibrational modes even at temperatures T ω. We also found that inelastic vibration-assisted Andreev reflections as well as quasiparticle tunneling induce a strong nonequilibrium state of the oscillator. In different ranges on the dot's level, we found that the current produces: (i) ground-state cooling of the oscillator with phonon occupation n 1, (ii) accumulation of energy in the oscillator with n 1, and (iii) a mechanical instability characterized by a negative damping coefficient. We show that ground-state cooling is achieved simultaneously for several modes of different frequencies. Finally, we discuss how the nonequilibrium vibrational state can be readily detected by the asymmetric behavior of the inelastic current peaks with respect to the gate voltage.

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Photon-assisted Andreev tunneling through a mesoscopic hybrid system

Cited by 89 publications

References 50 publications

Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads

Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads

Cavity Photons as a Probe for Charge Relaxation Resistance and Photon Emission in a Quantum Dot Coupled to Normal and Superconducting Continua

Charge-vibration interaction effects in normal-superconductor quantum dots

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