The ability to carry electric current with zero dissipation is the hallmark of superconductivity. This very property makes possible such applications ranging from magnetic resonance imaging machines to Large Hadron Collider magnets. But is it indeed the case that superconducting order is incompatible with dissipation? One notable exception, known as vortex flow, takes place in high magnetic fields. Here we report the observation of dissipative superconductivity in far more basic configurations: superconducting nanowires with superconducting leads. We provide evidence that in such systems, normal current may flow in the presence of superconducting order throughout the wire. The phenomenon is attributed to the formation of a non-equilibrium state, where superconductivity coexists with dissipation, mediated by the so-called Andreev quasiparticles. Besides the promise for applications such as single-photon detectors, the effect is a vivid example of a controllable non-equilibrium state of a quantum liquid. Thus our findings provide an accessible generic platform to investigate conceptual problems of out-of-equilibrium quantum systems.
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Discussions with X. Wang are warmly acknowledged. Experimental work at Minnesota was supported by the DOE Office of Basic Energy Sciences under Grant No. DE-FG02-02ER4600. Samples were fabricated in the Nano Fabrication Center, which receives funding from the NSF as a part of the National Nanotechnology Infrastructure Network, and were characterized in the Characterization Facility, University of Minnesota, a member of the NSF-funded Materials Research Facilities Network (http://www.mrfn.org) via the MRSEC program. AK was supported by DOE Contract No. DE-FG02-08ER46482.