Uniaxial pressure experiments on semiconductor heterostructures

    The aim of this project is to bring together the unique experimental expertise of the Dresden and Würzburg groups to attempt a class of experiment that has never previously been tried. One of the most successful methods of tuning semiconductor devices – in modern condensed matter physics including devices with topological properties – is by utilizing strain. Strain can be introduced either by epitaxial growth of crystalline layers on substrates with mismatched lattice parameters at the interface or mechanically. In a two-dimensional system this gives biaxial strain and effective biaxial internal stress [1,2]. One of the recent themes of experimental research at MPI-CPfS has been the development of new apparatus for applying high levels of uniaxial pressure [3,4]. A natural question to ask is how productive it would be to marry the two strands of research and apply high levels of uniaxial strain to semiconductor heterostructures and devices, either as an alternative or as a complement to epitaxial strain. If this could be done, a wealth of new physics would be in reach.

    Max Planck Fellow Laurens W. Molenkamp, a world-leading expert in semiconductor spintronics and the physics of topological materials, teams up with Dr. Hicks and Professor Mackenzie at MPI CPfS in offering this joint project to explore the best way of setting up the appropriate experiments through a combination of microstructuring of samples and careful design of appropriate uniaxial pressure apparatus. As such, it will involve developing design and processing skills that are ideal training for either an experimental physics career or one in industry.

    Successful candidates will register for PhD study at the University of Würzburg, where Prof. Molenkamp is based, and carry out research between Dresden and Würzburg as dictated by scientific priorities as the research unfolds. Willingness to travel between the two locations is therefore a prerequisite.

    [1]  C. Brüne, C. X. Liu, E. G. Novik, E. M. Hankiewicz, H. Buhmann, Y. L. Chen, X. L. Qi, Z. X. Shen, S. C. Zhang, and L. W. Molenkamp, Phys. Rev. Lett. 106, 126803 (2011)
    [2]  P. Leubner, L. Lunczer, C. Brüne, H. Buhmann, and L.W. Molenkamp, Phys. Rev. Lett. 117, 086403 (2016)
    [3] C.W. Hicks, M.E. Barber, S.D. Edkins, D.O. Brodsky, A.P. Mackenzie, Review of Scientific Instruments 85 (6), 065003 (2015)
    [4] A. Steppke, L. Zhao, M.E. Barber, T. Scaffidi, F. Jerzembeck, H. Rosner, A.S. Gibbs, Y. Maeno, S.H. Simon, A.P. Mackenzie, C.W. Hicks, Science 355 (6321), eaaf9398 (2017)

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