ABSTRACT
Tuning the complex interplay of electronic interactions, spin-spin correlations, and geometric phases of wavefunctions at microscopic length scales can endow materials with new macroscopic quantum properties. These include fractionalized quantum excitations and new forms of superconductivity, many of which promise applications such as topological quantum computation and energy-efficient electronic devices. Scanning tunneling microscopy experiments with their ability study the electronic and magnetic degrees of freedom atomically resolved are particularly well-suited to obtain microscopic insights on these phenomena. In this talk I will present some of our recent results on two-dimensional epitaxial topological heterostructures and moiré-superlattices, where we used such measurements to establish the presence of Majorana zero modes in the topological edge state of bismuth (111) [1] and to demonstrate strong electronic correlations in the flat bands of magic-angle twisted bilayer graphene [2]. I will conclude the talk with an outlook on how (scanning) tunneling spectroscopy experiments can be used to demonstrate the existence of gap-less Majorana modes as the fractionalized spin excitations of quantum spin liquids [3].
References
[1] B. Jäck et al., Science 364, 1255-1259 (2019).
[2] Y. Xie et al., Nature 572, 101–105 (2019).
[3] E.J. König et al., Phys. Rev. Lett. 125, 267206 (2020).
BIOGRAPHY
Berthold Jäck is an Assistant Professor of Physics and faculty member of the IAS Center Quantum Technologies at the Hong Kong University of Science and Technology. Before starting in Hong Kong in January 2021, he was a postdoctoral fellow of the Humboldt Foundation at Princeton University, where he was working with Prof. Ali Yazdani. Berthold received his PhD in physics from the Ecole Polytechnique Fédérale de Lausanne, Switzerland under the supervision of Prof. Klaus Kern at the Max-Planck-Institute for Solid State Research, Germany and he holds a diploma degree of nanotechnology with distinction from Würzburg University, Germany. His research is centered around the fabrication and microscopic investigation of low-dimensional quantum materials and the development of new microscopy techniques.
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