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Monday, March 23, 2015
3:00 PM - 4:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Colloquium

Noncentrosymmetric Metals: A New Materials Class for Artificial Multiferroic Design

James M. Rondinelli
Northwestern University

The metallic features in materials, which provide low-resistance channels for electrical conduction, lead to effective screening of local electric dipole moments. Itinerant electrons disfavor both dipole formation and cooperative ordering. Consequently, most metals with a finite density of states and partial band occupation exhibit centric (inversion symmetric) crystal structures. Despite this contraindication, noncentrosymmetric metals (NCSM) lacking inversion were proposed more than fifty years ago with some examples discovered serendipitously later [1]. In the first part of the talk, I describe a design framework to alleviate such property disparities and accelerate NCSM discovery: The primary ingredient relies on the removal of inversion symmetry through displacements of atoms whose electronic degrees of freedom are decoupled from the states at the Fermi level. Density functional theory calculations validate our crystal-chemistry strategy, and predict a polar-NCS perovskite ruthenate superlattice to be metallic and robust to spin-orbit interactions [2]. Next, I discuss a superlattice composed on the polar metal LiOsO3 that shares a similar electronic configuration [3], i.e., half-filled Os t2g orbitals weak electron-electron interactions that essential to sustaining the metallic state in bulk. I then propose how to turn this non-magnetic polar metal into a multiferroic through the design of a superlattice, which increases the degree of correlation, leading to Mott localization of the Os orbitals [4]. I conclude by summarizing new opportunities where noncentrosymmetric metals may serve as an ideal materials platform. [1] P. W. Anderson and E.I. Blount, “Symmetry Considerations on Martensitic Transformations: ‘Ferroelectric’ Metals?” Phys. Rev. Lett , 14, 217 (1965). [2] D. Puggioni, and J. M. Rondinelli, “Designing a robustly metallic noncenstrosymmetric ruthenate oxide with large thermopower anisotropy,” Nat. Commun., 5, 3432 (2014). [3] Y. Shi et. al., “A ferroelectric-like structural transition in a metal,” Nat. Mater., 12, 1024 (2013). [4] D. Puggioni, G. Giovannetti, M. Capone, J. M. Rondinelli, “Design of a Mott Multiferroic from a Non-Magnetic Polar Metal,” Submitted (2015).

Host: Turab Lookman