Seminars

  • Optical imaging of the valley dependent electron transport in MoS2

  • Speaker : 이지은/Jieun Lee
    Affiliation : 아주대학교/Department of Physics, Ajou University
    Date : May 24, 2018 2:00 PM
    Place : Buliding 110 Room N102
    Contact : noejung@unist.ac.kr
    Host : Prof.Noejung Park
  • Abstract

  • Atomically thin crystals, such as monolayer transition metal dichalcogenides (TMDCs), provide a new platform to investigate electrons in low dimensional solid-state systems. In these materials, two inequivalent energy band extrema occur at the edges of the Brillouin zone, known as valleys, which serve as a binary degree of freedom of electrons similar like spins. The unique control of valley pseudospins by electrical and optical means are not only fundamentally interesting, but may also find applications in valley-based electronics and optoelectronics.

    In this talk, we discuss methods to manipulate the valley degree of freedom of 2D TMDC materials. First, we describe the electrical generation of valley polarization through the valley Hall effect in monolayer molybdenum disulfide (MoS2). We use optical techniques to directly image the valley polarization accumulated at the edges of MoS2 channel with spatial resolution. We will also discuss the possibility to tune the valley Hall conductivity by controlling the crystal’s inversion symmetry in bilayer. Second, we describe the generation of current-driven valley magnetization in strained monolayer MoS2. The observed valley magnetization switches the sign when the direction of the in-plane bias flips and the magnitude scales with the amount of channel current. Lastly, we will discuss our recent results on mechanical control of valley magnetization.