MARVEL Distinguished Lecture — Alex Zunger

It will take place on Wednesday, October 20, 2021, 4 pm (CEST) on Zoom:

https://epfl.zoom.us/j/66438058915
Passcode: 2518

Spontaneous symmetry breaking in nominal cubic oxide perovskites through structural, magnetic or dipolar degrees of freedom

The impression that band theory would invariably predict an erroneous metallic state rather than the observed insulating phase for “Mott Insulators” has marked a significant shift in condensed matter theory some 75 years ago, placing strong emphasis of “electronic phases” in strongly correlated systems. Other microscopic degrees of freedom (m-DOF), such as lattice distortion (in para elastics), or the configurations of local magnetic moments (in paramagnets), and dipole moments (in para electrics), were considered as “spectator” DOF’s, being consequences of the primary electron correlation, and not a possible cause of the peculiarities of the electronic phases. We point out that when such a symmetry constrained view based on the smallest possible unit cell is avoided in mean field like DFT, two interesting consequences occur. First, some symmetry breaking lattice and magnetic m-DOF  that were previously observed experimentally in para phases emerge naturally as DFT energy -lowering effects. Second, the previously noted ‘false metal’ syndrome in Mott insulators disappears. The implications on our understanding of the nature of para phases as polymorphous networks having a distribution of local DOF’s will be discussed.

References: https://www.colorado.edu/faculty/zunger-matter-by-design/publications-0

About the speaker

Professor Alex Zunger’s research field is condensed matter theory of real materials, including contributions  to the development of basic tools of “first-principles theory of solids”, quantum materials, nanostructures, and solar photovoltaic materials. (see reference list). He received the 2018 Boer Solar Medal, the 2001 John Bardeen Award; the 2001 Rahman Award of the APS; the 2013 Hume-Rothery Award of the TMS (on “First Principles Alloy Theory”), and the inaugural 2011 Materials Theory Award of the MRS (on “inverse Design of materials”). His papers have received over 100,000 citations, having “h-number” of more than 150.

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