Transition metal dichalcogenides, excellent candidates for next generation technologies

PhD defence, Tuesday 20 February 2018. Arlette Sohanfo Ngankeu.

2018.02.20 | Karen Konradi

Arlette Sohanfo Ngankeu

Angle-resolved photoemission spectroscopy images of 1T-TaS2 taken at 90 meV below the Fermi level at different temperatures (at ≈ 340 K in the nearly commensurate charge density wave phase (left) and at ≈ 600 K in the normal phase (right)) and photon energies of 96 eV (left) and 75 eV (right).

During her studies, Arlette Sohanfo Ngankeu investigated both the three- and two-dimensional transition metal dichalcogenides, especially the bulk metallic (1T-TaS2) and both the semiconducting (WS2 and MoS2) and metallic (TaS2) materials in their single layer (SL) form. 1T-TaS2 develops series of charge density wave (CDW) transitions below some onset temperatures. Such effects are interesting for device applications, especially if a way could be found for electrically controlling the transition between each CDW phase. Arlette's research has focused on the three-dimensional electronic structure of 1T-TaS2 in each CDW phase and in/above the normal phase. Her experimental results largely confirm theoretical predictions, for example, the coexistence of the CDW phase with a nearly one-dimensional metallic dispersion perpendicular to the crystal planes. Furthermore, she investigated the electron-phonon coupling of SL WS2, MoS2 and TaS2.

The PhD degree was completed at the Department of Physics and Astronomy, Science and Technology, Aarhus University.


This résumé was prepared by the PhD student.


Time: Tuesday 20 February 2018 at 10.00
Place: Building 1525, room 626. Department of Physics and Astronomy, Ny Munkegade 120, Aarhus University, 8000 Aarhus C.
Title of dissertation:  Study of the Electronic Properties of Three- and Two-Dimensional Transition Metal Dichalcogenides
Contact information: Arlette Sohanfo Ngankeu, e-mail:, +45 5222 7691

Members of the assessment committee:
Professor Carsten Busse, Faculty of Physics, University of Siegen, Germany

Professor Isabella Gierz, Max Planck Institute for the structure and dynamics of Matter, Germany

Professor Georg Bruun (chair), Department of Physics and Astronomy, Aarhus


Main supervisor:

Professor Philip Hofmann, Department of Physics and Astronomy, Aarhus University

Language: The PhD dissertation will be defended in English

The defence is public.

The dissertation is available for reading at the Graduate School of Science and

Technology/GSST, Ny Munkegade 120, building 1520, rooms 128-134, 8000 Aarhus


PhD defence
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Revised 17.05.2018