Superconducting quantum point contacts

Abstract

We review our experiments on the electronic transport properties of atomic contacts between metallic electrodes, in particular superconducting ones. Despite ignorance of the exact atomic configuration, these ultimate quantum point contacts can be manipulated and well characterized in-situ. They allow performing fundamental tests of the scattering theory of quantum transport. In particular, we discuss the case of the Josephson effect.

Single-Quasiparticle Trapping in Aluminum Nanobridge Josephson Junctions

“…This "poisoning" of a conduction channel changes the critical current and the inductance of the junction. Previous work has measured QP trapping in few-channel quantum point contact junctions via switching measurements of the critical current [14][15][16]. In contrast, our approach realizes dispersive measurement of the Josephson inductance of many-channel nanobridge junctions.…”

Levitons in superconducting point contacts

“…Since the very first years following Josephson's prediction in 1962 [1], electronic transport through coupled superconductors has been widely studied [2][3][4]. Later on, thanks to the advances in nanofabrication processes, it became possible to realize the so-called superconducting quantum point contacts [5][6][7][8][9][10] (SQPCs), i.e. systems where two superconducting electrodes are connected by a narrow constriction whose length is much smaller than the superconducting coherence length.…”

Resonators coupled to voltage-biased Josephson junctions: From linear response to strongly driven nonlinear oscillations

“…6(a)], a fictitious particle runs periodically through a cycle of localized and de-localized motion: Starting somewhere in the low energy sector, it gets trapped quickly in one of the local minima of the potential close to the global minimum of V eff (ϕ) (6). It is then transferred up in energy by the driving term ∝ cos(ϕ + Ωt) while being trapped in this local well.…”

“…Accordingly, there has been a long tradition of studying non-linear phenomena in driven superconducting circuits, starting as early as the 1960s with the discovery of Shapiro steps 1 . While Shapiro-steps have remained a tool in exploring new directions in Josephson physics, for instance in atomic point contacts [2][3][4][5][6] , other nonlinear phenomena, like synchronization, have been investigated in arrays of JJs: as a test-bed for generic theory models to capture synchronization phenomena 7,8 , but as importantly with the prospect of applications as sources of more intense coherent radiation 9 , cf. also new developments using intrinsic arrays [10][11][12] .…”