University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Monday, February 15th 2016
Speaker: Ruihua He, Boston College
Subject: Angle-resolved Photoemission Spectroscopy Study of Emergent Phenomena in Correlated Materials
Note: change of time for seminar.

A central theme of modern condensed matter physics is to discover and understand emergent phenomena in quantum materials. These phenomena emerge only through the collective behavior of electrons due to their mutual interactions as well as interactions with other degrees of freedom inside the materials. In this talk, I will give two examples of the emergent phenomena which I have been studying with angle-resolved photoemission spectroscopy in recent years. The first one is the negative electronic compressibility. I will present our evidence for the first experimental case of such phenomenon in a bulk material—the electron-doped iridate—and discuss the obtained insights into its microscopic origin, which heralds an uncharted territory of negative compressibility research that potentially features a whole variety of bulk quantum materials. The second example is the pseudogap phenomena. I will show how our view about the nature of these phenomena in hole-doped cuprate superconductors has evolved in the past two decades and been finally converging into one that they signal a phase of matter which is fundamentally distinct from superconductivity and characterized by multiple broken symmetries. I will discuss our results contributing to this development as well as their implications particularly regarding the broken translation symmetry aspect of the still-mysterious pseudogap phase.

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