Condensed Matter Seminar: Xinxin Cai, Penn State University, “Magnetoresistance oscillations and the half-flux quantum state in mesoscopic samples of Sr2RuO4”

Spin-triplet superconductor Sr2RuO4 was predicted to support exotic objects such as half-quantum vortices, which carry a magnetic flux half of the flux quantum Phi 0=hc/2e. We report electrical transport measurements on micron-sized, doubly connected cylinders of Sr2RuO4 single crystals with the cylinder axis along the c axis. Large amplitude magnetoresistance oscillations were observed, revealing unconventional Little-Parks effect dominated by vortex crossing. The free energy barrier that controls the vortex crossing was modulated by the magnetic flux enclosed in the cylinder, an in-plane field, measurement current, and factors related to sample geometry. We observed distinct features on magnetoresistance oscillations resulting from the emergence of the half-quantum state in this material.