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New results from single-crystal quantum structures of Sr2RuO4†

In past few years we have worked on the fabrication and measurements of single-crystal quantum structures of odd-parity, spin-triplet superconductor Sr 2 RuO 4 using a combination of conventional and unconventional nanofabrication techniques. Among them, doubly connected mesoscopic rings were used to detect the presence of half-flux-quantum (h/4e) state and Josephson junctions between Sr 2 RuO 4 and a conventional s -wave superconductor the chiral surface currents. Measurements on the latter structure revealed so far an upper limit in the chiral surface current density much smaller than that predicted theoretically. For the mesoscopic rings of Sr 2 RuO 4 , preliminary evidence for the existence of half-flux-quantum (h/4e) magnetoresistance oscillations was found at low temperatures with the presence of an in-plane field and a large applied measurement current. The implications of our results will be discussed.

†Work done in collaboration with Xinxin Cai, Brian Zakrzewski, Yiqun A. Ying, David Fobes, Tijiang Liu, and Zhiqiang Mao, and supported by the US Department of Energy.