• 日時:2019年10月16日(火) 17:00-18:00
    • 講演者:Dr. Vladislav Kataev (Leibniz Institute for Solid State and Materials Research IFW Dresden, Germany)
    • 場所:理学研究科講義棟Z103
    • 講演タイトル:Probing spin-correlated quantum matter with electron spin resonance spectroscopy
    • 概要:Magnetic transition metal ions located at the regular sites of a crystalline solid may build up strongly correlated spin networks of different spatial dimensionality. Depending on the specifics of the chemical bonding and certain geometrical constraints, zero-dimensional (OD) spin clusters, 1D spin chains and ladders, 2D spin planes, or even more complex 3D spin structures can be realized in a number of materials. An interplay between spin, orbital, charge and lattice degrees of freedom in these strongly correlated quantum magnets yields such spectacular phenomena ashigh temperature superconductivity, colossal magnetoresistance, multiferroic order, metal-insulator and quantum phase transitions, quantum spin liquid states, magnetic memory effects and others. For all these reasons the field of quantum magnetism in condensed matter physics is continuously expanding and currently attracts a lot of interdisciplinary interest.
        High magnetic field electron spin resonance (ESR) spectroscopy has emerged as an instructive tool to investigate the low-energy spin dynamics, energy spectrum of the spin states and the spin structure of the ordered phases in a broad class of strongly correlated spin systems, which is of paramount importance for the comprehensive understanding of the above mentioned phenomena. In this talk, recent experiments conducted at the IFW Dresden on quasi-2D van der Waals crystals of α-RuCl3 will be discussed with a particular focus on the properties of the novel, magnetic field-induced spin liquid phase where signatures of unconventional fractionalization of magnetic excitations into the elusive Majorana fermions have been obtained.

    • 日時:2019年5月21日(火) 15:30-16:30
    • 講演者:嘉部量太先生(九州大学OPERA)
    • 場所:理学研究科講義棟Z301
    • 講演タイトル:有機蓄光システムの開発
    • 概要:蓄光材料は非常誘導灯や時計などの光源として実用化されている。既存の蓄光材料は全て無機材料で構成されており、耐久性・発光特性に優れる一方で、 希土類や高温焼成過程を必要とすること、透明性の付与が容易ではないことなどの課題も残されている。一方、我々は有機材料の電荷分離状態に着目し、世界初の有機蓄光システムを見出した。 有機蓄光システムは上記の課題を解決可能であり、新しい蓄光材料としての利用が期待される。本講演では有機蓄光の発光メカニズムや、従来のりん光発光との違いについても紹介する。