Gate tuning of 2D Quantum Materials

2D quantum materials are a promising platform that allow for unprecedented control over their quantum states at atomic length scales. A wide variety of striking physical properties have been realised, including superconductivity, charge density-wave states and long-range magnetic order. Many of them are known to be sensitive to changes in carrier density, opening powerful routes for the control of these physical properties [1]. As part of the class of van der Waals materials, they are also ideal systems for fabricating in single-layer structures, as for graphene, but the resulting influence of such thickness reduction on their many-body states and phases is only just starting to be understood and explored.

In this project, you will work in St Andrews on the fabrication of 2D quantum materials using our state-of-the-art molecular beam epitaxy system, and will study the electronic structure of the resulting monolayers using lab- and synchrotron-based angle-resolved photoemission spectroscopy [2-4]. In collaboration with the Dresden team, you will seek to form field-effect device structures from these films [5,6], in order to gain new levels of control and understanding on the interacting states in 2D quantum materials. Specific systems of interest include transition metal dichalcogenides and 2D magnets. The combined characterization approach will allow correlating changes of electronic structure with transport properties, and the gate-tuning of their collective states, with the ultimate goal to realise in situ measurements of the electronic structure under such gating control.

This project will involve performing experiments utilizing the state-of-the-art facilities of the Centre for Designer Quantum Materials in St Andrews and of the MPI-CPFS in Dresden. A majority of the experimental work will be performed in St Andrews and at synchrotron, but in close collaboration with colleagues at MPI-CPFS. Candidates should have an excellent understanding of solid state physics, and be motivated to work in a highly collaborative research environment.


[1] L.J. Li, E.C.T. O’Farrell, K.P. Loh, G. Eda, B. Özyilmaz, and A.H. Castro Neto
Controlling many-body states by the electric-field effect in a two-dimensional material
Nature 529, 185–189 (2016)
[2] J. M. Riley, F. Mazzola, M. Dendzik, M. Michiardi, T. Takayama, L. Bawden, C. Granerød, M. Leandersson, T. Balasubramanian, M. Hoesch, T.K. Kim, H. Takagi, W. Meevasana, Ph. Hofmann, M.S. Bahramy, J.W. Wells, and P.D.C. King
Direct observation of spin-polarized bulk bands in an inversion-symmetric semiconductor
Nature Physics 10, 835–839 (2014)
[3] J.M. Riley, W. Meevasana, L. Bawden, M. Asakawa, T. Takayama, T. Eknapakul, T.K. Kim, M. Hoesch, S.-K. Mo, H. Takagi, T. Sasagawa, M.S. Bahramy, and P.D.C. King
Negative electronic compressibility and tunable spin splitting in WSe2
Nature Nanotechnology 10, 1043–1047 (2015)
[4] M.D. Watson, A. Rajan, T. Antonelli, K. Underwood, I. Marković, F. Mazzola, O.J. Clark, G.-R. Siemann, D. Biswas, A. Hunter, S. Jandura, J. Reichstetter, M. McLaren, P. Le Fèvre, G. Vinai, and P.D.C. King
Strong-coupling charge density wave in monolayer TiSe2
2D Materials 8, 015004 (2020)
[5] D. Costanzo, H. Zhang, B.A. Reddy, H. Berger, and A.F. Morpurgo
Tunnelling spectroscopy of gate-induced superconductivity in MoS2
Nature Nanotechnology 13, 483–488 (2018)
[6] H. Zhang, C. Berthod, H. Berger, T. Giamarchi, and A.F. Morpurgo
Band Filling and Cross Quantum Capacitance in Ion-Gated Semiconducting Transition Metal Dichalcogenide Monolayers
Nano Lett. 19, 8836–8845 (2019)

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