High-performance Andreev interferometer based electronic coolers

We propose an electronic refrigerator based on a ballistic Andreev interferometer that can reach a maximum cooling power per channel up to five orders of magnitude larger than that of the conventional normal metal-insulator-superconductor cooler. This effect is achieved by exploiting the destructive interference that occurs when the superconducting phase difference equals pi. This results in a strongly suppressed charge current below the superconducting gap, while still allowing the extraction of excitations above the gap, leading to a cooler with enhanced performance. Interestingly, we find that such a large cooling power per channel enables the achievement of an electronic temperature close to the theoretical lower bound. Additionally, we derive an approximate expression for this bound in the regime of low bath temperatures. Finally, we propose potential implementations of the ballistic Andreev interferometer cooler using semiconductors, graphene, and topological insulators.