Supercurrent in a Double Quantum Dot

Saldaña, Juan Carlos Estrada; Vekris, Alexandros; Steffensen, G.; Žitko, Rok; Krogstrup, Peter; Paaske, Jens; Grove-Rasmussen, Kasper; Nygård, Jesper

doi:10.1103/physrevlett.121.257701

Cited by 56 publications

(67 citation statements)

References 61 publications

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“…where n kσ (0) = [1 + exp ((ε Nkσ − µ N )/k B T )] −1 is the Fermi distribution function for the normal lead electrons. We have solved numerically these coupled differential equations (8)(9)(10)(11)(12)(13)(14)(15)(16)(17) subject to the specific initial conditions. For convenience, we have assumed that till t < 0 both external reservoirs were isolated from the quantum dots.…”

Section: Equations Of Motionmentioning

confidence: 99%

Subgap Dynamics of Double Quantum Dot Coupled Between Superconducting and Normal Leads

Baran

Taranko

Domański

2021

Preprint

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Dynamical processes induced by the external time-dependent fields can provide valuable insight into the characteristic energy scales of a given physical system. We investigate them here in a nanoscopic heterostructure, consisting of the double quantum dot coupled in series to the superconducting and the metallic reservoirs, analyzing its response to (i) abrupt bias voltage applied across the junction, (ii) sudden change of the energy levels, and imposed by (iii) their periodic driving. We explore subgap properties of this setup which are strictly related to the in-gap quasiparticles and discuss their signatures manifested in the time-dependent charge currents. The characteristic multi-mode oscillations, their beating patters and photon-assisted harmonics reveal a rich spectrum of dynamical features that might be important for designing the superconducting qubits.

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Section: Equations Of Motionmentioning

confidence: 99%

Subgap Dynamics of Double Quantum Dot Coupled Between Superconducting and Normal Leads

Baran

Taranko

Domański

2021

Preprint

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“…Their main effect is to smooth out these phase transitions, which is already observable at typical base temperatures of 𝑇 ≈ 15-50 mK being small against Γ/𝑘 𝐵 (ranging from 0.1-1 meV/k B ≈ 1-10 K). 24,26,87 For instance, this can be appreciated in figure 4(a) showing the total spin quantum number 𝑠 obtained from the thermal average 𝑺 2 POL = ℏ 2 𝑠(𝑠 + 1) over the electronic subsystem. 88 Here, 𝑺 = (ℏ/2) 𝛼𝑠𝑠 𝑑 † 𝛼𝑠 𝝈 𝑠𝑠 𝑑 𝛼𝑠 denotes the spin operator with 𝝈 being the vector of Pauli matrices.…”

Section: Thermal Broadening Of Phase Transitionsmentioning

confidence: 99%

“…[11][12][13][14] The QDs' highly tunable electronic spectra [15][16][17][18] makes them in particular interesting for low-dissipation superconducting spintronics 19,20 and quantum computation. 21,22 Ground-state (GS) transitions in such systems have been observed [23][24][25][26] and discussed in terms of the spin-orbit interaction 27,28 , topological protection, [29][30][31][32][33] and nonequilibrium transport. [34][35][36][37] Remarkably, it was recently demonstrated in carbon nanotube (CNT) quantum dot setups that the electron-phonon interaction can be tailored electrostatically, to even attain attractive electron interaction.…”

Section: Introductionmentioning

confidence: 99%

Resonator induced quantum phase transitions in a hybrid Josephson junction

Hussein,

Belzig

2021

Preprint

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We investigate the Josephson current through a suspended carbon nanotube double quantum dot which, at sufficiently low temperatures, is characterized by the ground state of the electronic subsystem. Depending on parameters like a magnetic field or the inter-dot coupling, the ground state can either be a current-carrying singlet or doublet, or a blockaded triplet state. Since the electron-vibration interaction has been demonstrated to be electrostatically tuneable, we study in particular its effect on the current-phase relation. We show that the coupling to the vibration mode can lift the current-suppressing triplet blockade by inducing a quantum phase transition to a ground state of a different total spin. Our key finding is the development of a triple point in the Josephson current parameterized by the resonator coupling and the Josephson phase. The quantum phase transitions around the triple point are directly accessible through the critical current and resilient to moderately finite temperatures. The proposed setup makes the mechanical degree of freedom part of a superconducting hybrid device which is interesting for ultra-sensitive displacement detectors.

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“…S1. Lever-arm parameter calibration, demonstration of G tunability by the plunger gate, supercurrent enhancement of the linear conductance, and determination of U. References (36)(37)(38)(39)(40)…”

Section: Supplementary Materialsmentioning

confidence: 99%

Charge localization and reentrant superconductivity in a quasi-ballistic InAs nanowire coupled to superconductors

et al. 2019

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A semiconductor nanowire with strong spin-orbit coupling in proximity to a superconductor is predicted to display Majorana edge states emerging under a properly oriented magnetic field. The experimental investigation of these exotic states requires assessing the one-dimensional (1D) character of the nanowire and understanding the superconducting proximity effect in the presence of a magnetic field. Here, we explore the quasi-ballistic 1D transport regime of an InAs nanowire with Ta contacts. Fine-tuned by means of local gates, the observed plateaus of approximately quantized conductance hide the presence of a localized electron, giving rise to a lurking Coulomb blockade effect and Kondo physics. When Ta becomes superconducting, this local charge causes an unusual, reentrant magnetic field dependence of the supercurrent, which we ascribe to a 0 - π transition. Our results underline the relevant role of unintentional charge localization in the few-channel regime where helical subbands and Majorana quasi-particles are expected to arise.

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Supercurrent in a Double Quantum Dot

Cited by 56 publications

References 61 publications

Subgap Dynamics of Double Quantum Dot Coupled Between Superconducting and Normal Leads

Subgap Dynamics of Double Quantum Dot Coupled Between Superconducting and Normal Leads

Resonator induced quantum phase transitions in a hybrid Josephson junction

Charge localization and reentrant superconductivity in a quasi-ballistic InAs nanowire coupled to superconductors

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