Edward A. Bouchet Award Talk: Controlling Dissipation in Superconductors: the Oxymoron that Leads to New Superconducting Phases and Transitions

In this Bouchet Award talk, I will first briefly discuss why I feel that it is important to balance research, service, and outreach. I will then discuss my research on “dissipative” superconducting systems. In particular, superconductors are exciting materials for basic physics and applications because they conventionally exhibit zero-resistance and zero-dissipation. In contrast, unconventional superconductors—including high-temperature superconductors and hybrid superconductor-normal (S-N) systems relevant to quantum computation—combine superconductivity with dissipative normal metal-like states. Yet dissipation has been difficult to control and parametrize. Here, I will discuss electrical transport experiments on hybrid superconductor-normal metal systems where the dissipation is controlled, leading to new understanding of superconducting states and transitions. In particular, I will show how superconductivity is established in granular S-N systems, how metallic states appear in arrays of S-N systems as the normal metal fraction is increased, and how magnetic fields can be used to control a variety of dissipative phase transitions. The results are relevant to understanding the role of dissipation in superconducting systems, and in correlated materials in general.