Andreev reflection mediated $Δ_T$ noise

Abstract: Quantum noise plays a pivotal role in understanding quantum transport phenomena, including current correlations and wave-particle duality. A recent focus in this domain is $\Delta_T$ noise, which arises due to a finite temperature difference in the absence of charge current at zero voltage bias. This paper investigates $\Delta_T$ noise in mesoscopic hybrid junctions with insulators, where the average charge current is zero at zero voltage bias, through the measurement of quantum shot noise, i.e., $\Delta_T$ noise. Notably, we find that the $\Delta_T$ noise in metal-insulator-superconductor junctions is significantly larger than in metal-insulator-metal junctions. Furthermore, our results reveal that $\Delta_T$ noise initially increases with barrier strength, peaks, and then decreases, while it shows a steady increase with temperature bias, highlighting the nuanced interplay between barrier characteristics and thermal gradients.