Colloquium

  • Emerging Phenomena in Complex Oxide Thin Films: Polar Metal (전이금속 산화물 박막에서의 새로운 현상: 극성 도체)

  • Speaker : 김태헌 / Tae Heon Kim
    Affiliation : Department of Physics, University of Ulsan
    Date : November 8, 2017 4:00 PM
    Place : Building 110 Room N103
    Contact : ysoh@unist.ac.kr
    Host : Yoon Seok Oh
  • Abstract

  • Complex materials have been fertile ground for new discoveries, particularly due to their wide-ranging electronic, optical, and magnetic properties [1]. For several decades, transition metal oxide (TMO) compounds have offered a great opportunity to research fields for materials science as well as condensed-matter physics [1,2]. Note that the transition-metal atom has a d-shell electronic configuration with strong interactions between spin, charge, orbital and lattice degrees of freedom. In particular, artificial TMO heterostructures, where TMO compounds are not only epitaxially but also geometrically constrained by the underlying substrates with layered structures, have been served as a synthetic route to control the electronic, magnetic, and crystallographic structures [2,3]. Using atomic-scale heteroepitaxy in TMO thin-film/superlattice growth [3], unexpected changes in the lattice and transport properties, which are unattainable in the bulk counterparts, can be made leading to new modalities for control and optimization of known states and leading to the emergence of exotic states [4,5]. Various control knobs have been exploited to achieve new physical phenomena in the artificial TMO heterostructures with strongly-correlated d-band electrons such as lattice deformation by misfit strain, dimensionality by thickness control, symmetry conversion via crystallographic orientation, polar discontinuity at a heterointerface, and so forth.
    Here, some of fascinating physical phenomena in complex oxide thin films will be briefly introduced. Among them, I will demonstrate design principles and synthetic strategies for the realization of an emerging polar metallic state where electrical dipole moments and delocalized charge carriers coexist in a single material.