Abstract
Charge interference (Aharonov-Casher effect) in a long superconducting quantum phase slip wire is considered, and from this the ``dual'' Fraunhofer interference effect (dual to the critical current modulation of a short Josephson junction in an external magnetic field) is derived. The device that can be used to observe this effect is proposed. Furthermore, the impact of wire inhomogeneities, charge disorder, and noise on the phase slip amplitude is investigated. Although intrinsically protected against small fluctuations, the Aharonov-Casher interference resulting from jumps of random offset charges and quasiparticles can result in significant fluctuations of the measured current-voltage characteristics of the quantum phase slip wire, similar to the effects of Joule heating when averaged out over many fluctuations. Possible ways to identify and mitigate such disorder are discussed.
Highlights
Significant efforts have been made in the past decades to observe so-called “dual” Shapiro steps, an important milestone towards realizing a quantum current standard, dual to that of the Josephson volt [1,2]
The coherent quantum phase slips (CQPS) dual of the well-known Fraunhofer interference in short Josephson junctions has been derived, and it is shown how this interference arises from the AharonovCasher effect in long CQPS wires
The charge noise spectral density was shown to enter into the fluctuations of the phase slip rate, and how the phase slip rate is affected by local disorder was investigated
Summary
Significant efforts have been made in the past decades to observe so-called “dual” Shapiro steps, an important milestone towards realizing a quantum current standard, dual to that of the Josephson volt [1,2]. The AC effect has been demonstrated experimentally for phase slips in Josephson junction rings [10] and networks [12,26] as well as for CQPS in devices made of continuous superconducting wires [27,28,29], yet the appearance of the direct dual to the diffraction effects in Josephson junctions is lacking Such an effect would form striking evidence for CQPS in transport measurements of superconducting nanowires. An approximate picture can be used to provide an intuitive description of the AC effect In this picture, the CQPS wire consists of a chain of N capacitively coupled islands [Fig. 1(a)], and phase slips (fluxon tunneling) are permitted in between these islands [17]. For a homogeneous wire dominated by order parameter disorder [33,34] the BCS coherence length ξ0 forms the relevant length scale
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