Charge carrier control in 2D Quantum Materials

Transition-metal dichalcogenides (TMDs) support a wide variety of striking physical properties in bulk, such as superconductivity and charge density-wave states. These are known to be sensitive to changes in carrier density, opening powerful routes for their control [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 combine epitaxial growth via molecular-beam epitaxy [2], spectroscopic studies using angle-resolved photoemission [3-5], and transport measurements including electrolyte gating [6-7] in order to gain new levels of control and understanding on the interacting states in monolayer TMDs. This combined approach will allow correlating changes of electronic structure with transport properties, gate-tuning of their collective states, and ultimately aims to develop new routes towards the “on-demand” control of the exotic physical properties of 2D quantum materials. 

This project will involve performing experiments utilizing the state-of-the-art facilities both of the Centre for Designer Quantum Materials in St Andrews and of the Max-Planck Institute for the Chemical Physics of Solids in Dresden. In addition, some experiments will be performed at international synchrotron facilities. Candidates should have an excellent understanding of solid state physics, and be motivated to work in a highly collaborative research environment.

References

[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] A. Rajan, K. Underwood, F. Mazzola, and P.D.C. King
Morphology control of epitaxial monolayer transition metal dichalcogenides
Phys. Rev. Materials 4, 014003 (2020)
[3] 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)
[4] 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)
[5] 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
accepted for publication in 2D Materials
[6] 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)
[7] 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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