Description:

Professor Pallab Goswami, Northwestern University

Title: Competing multipolar orders and topology for 227 pyrochlore iridates

Abstract: At low temperatures, the interplay between electronic interaction and spin orbit coupling can lead to competing broken symmetry phases with nontrivial band topology, exotic quantum critical phenomena and non-Fermi properties. 227 pyrochlore iridates can provide a suitable material platform for studying such emergent phenomena. In this talk, I will discuss the recent experimental and theoretical development for this class of transition metal oxides. By focusing on the normal state, described by a semimetal with quadratic touching between Kramers degenerate conduction and valence bands, I will apply renormalization group analysis, mean-field theory, and phenomenological Landau theory as three complementary methods to construct a global phase diagram of these materials in the presence of generic local interactions among itinerant 5d electrons of Ir ions. The global phase diagram can support competing multipolar orders such as metallic spin ice, all in-all out and nematicity. I will emphasize our predictions for enigmatic time reversal symmetry breaking phase of Pr2Ir2O7 in terms of metallic spin ice and the general applicability of the theoretical framework for other strongly correlated materials such as half-Heusler compounds.