Angle-resolved photoelectron spectroscopy of chiral topological semimetals and Majorana heterostructures

Angle-resolved photoelectron spectroscopy (ARPES) at relatively low photon energies (~20-150 eV) has become the canonical tool for the study of Fermi-arc surface states in topological semimetals. Using synchrotron radiation in the soft X-ray energy regime allows us to gain complementary information about their bulk band structure. Here, I will report recent results from our investigation of chiral topological semimetals (CTSs), which revealed new multifold quasiparticles with large Chern numbers [1] that may be used in the future to realize exotic proposals in these materials, such as a quantized response to circularly polarized light [2,3]. I will furthermore show how a detailed analysis of Fermi-arc dispersion in CTSs can not only reveal the magnitude, but also the sign of the Chern number of multifold Fermions at different high symmetry points in the Brillouin zone, which can be used for crystallography. Finally, I will also report our recent advances in thin film growth and characterization of semiconductor/superconductor heterostructures where we have found a route for tuning the band offset at the interface, which may have important applications in Majorana zero mode devices that can be used for topological quantum computing.

References:
[1] N.B.M. Schröter, et al. "Chiral topological semimetal with multifold band crossings and long Fermi arcs." Nature Physics (2019) [2] F. de Juan, et al. “Quantized circular photogalvanic effect in Weyl semimetals”. Nat. Commun. 8, 15995 (2017).
[3] D. Rees et al., “Quantized Photocurrents in the Chiral MultifoldFermion System RhSi” arXiv:1902.03230v1