University of Minnesota
School of Physics & Astronomy

Academic Calendar

Thursday, March 9th 2017
11:00 am:
Thesis Defense in PAN 110
Speaker: Yangmu Li
Subject: New insights into phase diagram and the emergence of superconductivity for the electron-doped cuprate superconductors
This is the public portion of Mr. Li's thesis defense. His advisor is Professor Martin Greven.

After three decades of enormous scientific inquiry, the emergence of superconductivity in the cuprates remains an unsolved puzzle. One major challenge has been to arrive at a satisfactory understanding of phase transitions in the multi-parameter phase space. A related challenge has been to achieve a unified understanding of the hole- and the electron-doped compounds. Here, I report detailed neutron scattering, muon spin rotation/relaxation and magnetoresistivity measurements for the archetypal electron-doped cuprate Nd2-xCexCuO4+d that, in combination with prior data, provide crucial links between the normal and superconducting states and between the electron- and the hole-doped parts of the phase diagram. The revised electron-doped side of the phase diagram features a disorder-smeared first-order phase transition between the antiferromagnetic and bulk superconducting ground states. The characteristics of the normal state and those of the superconducting state consistently indicate two-band (electron and hole) features and clearly point to hole-driven superconductivity in these nominally electron-doped materials. These insights allow us to extend the Uemura-scaling between the superconducting transition temperature and the hole superfluid density to the electron-doped cuprates.

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