Colloquium

  • Optical Studies of Valley States in 2D Transition Metal Dichalcogenides (2차원 전이금속 이황화화물 내의 밸리/스핀 동역학 연구)

  • Speaker : 김종환 / Jonghwan Kim
    Affiliation : Department of Materials Science and Engineering, POSTECH
    Date : November 22, 2017 4:00 PM
    Place : Building 110 Room N103
    Contact : kpkim@unist.ac.kr
    Host : Kwanpyo Kim
  • Abstract

  • The valley degree of freedom in 2D transition metal dichalcogenides (TMD) recently emerged as a novel information carrier in addition to spin and charge. The valley electronic states are shown to be easily accessible via circular polarization of photoexcitation. In addition, the intrinsic valley lifetime is expected to be remarkably long due to the unique spin-valley locking behavior. Here, we report efficient generation of microsecond-long lived valley polarization via ultrafast charge transfer process in WSe2/MoS2 heterostructures. This valley polarization has near unity degree and several orders of magnitude longer lifetime than previously reported values. Our ultrafast optical studies reveal promising potential of valley electronic states in TMD monolayers for novel valleytronics and spintronics applications.