Electronic and structural phase transitions in layered transition metal dichalcogenides

Recently, layered transition metal dichalcogenides (LTMDs) have attracted considerable interest of the materials science and condensed matter communities. One of the reasons for that is their layered nature which allows for bulk crystals to be exfoliated down to monolayer forms, similarly to graphene. Interestingly, within the single layer, almost all of the over 40 materials from this group fall into one of two arrangements, either trigonal prismatic or octahedral, of the chalcogen atoms surrounding the transition metal site. The two arrangements compete with each other energetically and the choice of the more stable configuration is related to the number of d-electrons provided by the transition metal. At the same time, LTMDs as a group display a broad range of electronic properties, from semiconducting to metallic, including superconducting phases at low temperatures. Moreover, the strong link between electron configuration and the lattice symmetry leads to the appearance of charge-density waves in some of the metallic LTMDs as well as Jahn-Teller lattice distortions in some semiconducting ones.

In this project, you will use both analytical and ab initio methods to describe the electronic properties of the layered transition metal dichalcogenides. You will explore the connection between electrons and lattice symmetry in those materials and develop models to describe the links and transitions between various electronic and crystalline phases. Finally, you will investigate whether such transitions can be induced by external factors like pressure, doping or laser irradiation. Such phase tuning would be accompanied by the respective changes in the local or global electronic/phononic properties of the material (for example, turning a semiconducting flake into a metallic one as a result of its “switching” between two crystal structures with different electronic band structures) and might be interesting for optoelectronic, spintronic or energy applications.

The project will be realised within the group led by Dr Marcin Mucha-Kruczynski and might involve collaboration with other theoretical or experimental groups in the UK or abroad. For more detailed information on the research, please visit http://people.bath.ac.uk/mlmk20/.

The successful candidate should hold, or expect to receive, a first class or good 2.1 Master’s degree (or equivalent) in Physics (Theoretical Physics preferred) or Theoretical/Quantum Chemistry (or other closely related field). A keen interest in theoretical condensed matter physics and a strong work ethic are essential. Also required is basic programming experience as well as some knowledge of Matlab/Mathematica.

Informal enquiries should be directed to Dr Marcin Mucha-Kruczynski ([Email Address Removed]).

Formal applications should be made via the University of Bath’s online application form for a PhD in Physics:
https://www.bath.ac.uk/samis/urd/sits.urd/run/siw_ipp_lgn.login?process=siw_ipp_app&code1=RDUPH-FP01&code2=0012

More information about applying for a PhD at Bath may be found here:
http://www.bath.ac.uk/guides/how-to-apply-for-doctoral-study/