Persistent Current in Superconducting Nanorings

Матвеев, К. А.; Larkin, A. I.; Glazman, L. I.

doi:10.1103/physrevlett.89.096802

Cited by 242 publications

(306 citation statements)

References 14 publications

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“…The only source of coupling between different rhombi is the periodic boundary condition along the chain. The method to treat similar problem was developed recently by Matveev, Larkin and Glazman [5] (MLG). They considered simple chain of N Josephson junctions in the closed-ring geometry, and reduced calculation of supercurrent in large-N limit to the solution of a Schröedinger equation for a particle moving in a periodic potential ∼ cos x, with appropriate boundary condition.…”

Section: Introductionmentioning

confidence: 99%

Anomalous periodicity of supercurrent in long frustrated Josephson-junction rhombi chains

Protopopov

Фейгельман

2004

Phys. Rev. B

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We consider a chain of Josepshon-junction rhombi (proposed originally in [1]) in quantum regime, and in the realistic case when charging effects are determined by junction capacitances. In the maximally frustrated case when magnetic flux through each rhombi Φ r is equal to one half of superconductive flux quantum Φ 0 , Josepshon current is due to correlated transport of pairs of Cooper pairs, i.e. charge is quantized in units of 4e. Sufficiently strong deviation δΦ ≡ |Φ r − Φ 0 /2| > δΦ c from the maximally frustrated point brings the system back to usual 2e-quantized supercurrent.We present detailed analysis of Josepshon current in the fluctuation-dominated regime (sufficiently long chains) as function of the chain length, E J /E C ratio and flux deviation δΦ. We provide estimates for the set of parameters optimized for the observation of 4e-supercurrent.

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Section: Introductionmentioning

confidence: 99%

Anomalous periodicity of supercurrent in long frustrated Josephson-junction rhombi chains

Protopopov

Фейгельман

2004

Phys. Rev. B

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“…The quantum phase slips (QPS) in the junctions can be viewed as the charge-sensitive fluxon tunneling [9,10] provided the conditions discussed below are satisfied. Microwave experiments [11] have demonstrated that dephasing of a fluxonium, a small Josephson junction shunted by a 1D Josephson chain, can be due to the effect of fluctuating charges on the QPS in the chain.…”

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confidence: 99%

Spectroscopic Evidence of the Aharonov-Casher Effect in a Cooper Pair Box

et al. 2016

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We have observed the effect of the Aharonov-Casher (AC) interference on the spectrum of a superconducting system containing a symmetric Cooper pair box (CPB) and a large inductance. By varying the charge ng induced on the CPB island, we observed oscillations of the device spectrum with the period ∆ng = 2e. These oscillations are attributed to the charge-controlled AC interference between the fluxon tunneling processes in the CPB Josephson junctions. The measured phase and charge dependences of the frequencies of the |0 → |1 and |0 → |2 transitions are in good agreement with our numerical simulations. Almost complete suppression of the tunneling due to destructive interference has been observed for the charge ng = e(2n + 1). The CPB in this regime enables fluxon pairing, which can be used for the development of parity-protected superconducting qubits.The Aharonov-Casher (AC) effect is a non-local topological effect: the wave function of a neutral particle with magnetic moment moving in two dimensions around a charge acquires a phase shift proportional to the charge [1]. This effect has been observed in experiments with neutrons, atoms, and solid-state semiconductor systems (see, e.g., [2][3][4] and references therein). Similar effects have been predicted for superconducting networks of nanoscale superconducting islands coupled by Josephson junctions. For example, the wave function of the flux vortices (fluxons) moving in such a network should acquire a phase that depends on the charge on superconducting islands [5]. Indeed, oscillations of the network resistance in the flux-flow regime have been observed as a function of the gate-induced island charge [6]; these oscillations have been attributed to the interference associated with the AC phase. However, this attribution is not unambiguous, because qualitatively similar phenomena can be produced by the Coulomb-blockade effect due to the quantization of charge on the superconducting islands [7].More recently, indirect evidence for the AC effect in superconducting circuits has been obtained in the study of suppression of the macroscopic phase coherence in onedimensional (1D) chains of Josephson junctions by quantum fluctuations [8]. The quantum phase slips (QPS) in the junctions can be viewed as the charge-sensitive fluxon tunneling [9,10] provided the conditions discussed below are satisfied. Microwave experiments [11] have demonstrated that dephasing of a fluxonium, a small Josephson junction shunted by a 1D Josephson chain, can be due to the effect of fluctuating charges on the QPS in the chain. Applications of the AC effect in classical Josephson devices have been discussed in Refs. [7,12].In this Letter we describe microwave experiments which provide direct evidence for the charge-dependent interference between the amplitudes of fluxon tunneling. We have studied the microwave resonances of the device consisting of two nominally identical Josephson junctions separated by a nanoscale superconducting island (the socalled Cooper-pair box, CPB) and a large inductanc...

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“…The allowed states of a superconducting ring differ by the phase change accumulated over the circumference of the loop. The energy of the n-th state is given by [6]:…”

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confidence: 99%

Normal-metal–insulator–superconductor interferometer

Arutyunov

Hongisto

2004

Phys. Rev. B

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Hybrid normal metal -insulator -superconductor microstructures suitable for studying an interference of electrons were fabricated. The structures consist of a superconducting loop connected to a normal metal electrode through a tunnel barrier . An optical interferometer with a beam splitter can be considered as a classical analogue for this system. All measurements were performed at temperatures well below 1 K. The interference can be observed as periodic oscillations of the tunnel current (voltage) through the junction at fixed bias voltage (current) as a function of a perpendicular magnetic field. The magnitude of the oscillations depends on the bias point. It reaches a maximum at energy eV which is close to the superconducting gap and decreases with an increase of temperature. Surprisingly, the period of the oscillations in units of magnetic flux ∆Φ is equal neither to h/e nor to h/2e, but significantly exceeds these values for larger loop circumferences. The origin of the phenomena is not clear.

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Persistent Current in Superconducting Nanorings

Cited by 242 publications

References 14 publications

Anomalous periodicity of supercurrent in long frustrated Josephson-junction rhombi chains

Anomalous periodicity of supercurrent in long frustrated Josephson-junction rhombi chains

Spectroscopic Evidence of the Aharonov-Casher Effect in a Cooper Pair Box

Normal-metal–insulator–superconductor interferometer

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