Electronic noise generated by a temperature gradient across a hybrid normal metal–superconductor nanojunction

Abstract

Understanding electronic noise in hybrid junctions is essential for designing efficient nanoscale electronics at the quantum limit. Recently, a new (previously overlooked) noise contribution, generated by the temperature difference across a conducting heterostructure and denoted as delta-T noise, was predicted and revealed experimentally in atomic-scale contacts (Shein Lambroso et al. in Nature 562:240–244, 2018). While the new type of electronic noise and the well-known voltage-generated shot noise have the same partition origin, they are activated by different stimuli. In the paper by Shein Lambroso et al. (2018), transmission probabilities for electrons flowing through the considered setups were assumed to be constant, a very good approximation for normal metal contacts within the used temperature range. In this work, we propose and study theoretically the delta-T noise in hybrid normal metal–superconductor nanojunctions where it has to be more pronounced at low temperatures due to the strongly nonlinear energy dependence of interface scattering characteristics in the gap region. Such experiments can be useful to probe quantum effects and to reveal small temperature variations along electronic nanoscale circuits.