Defence of Thesis 9th October 2026: Stefanie Suzanne Brinkman – Faculty of Natural Sciences

Doctoral Candidate Stefanie Suzanne Brinkman at the Department of Physics will hold a trial lecture and defend her doctoral thesis for the degree of Philosophiae Doctor (PhD). Thesis title “Electronic Structure of Low-Symmetry Quantum Materials Studied by Angle-Resolved Photoemission” Trial lecture Assigned topic: “The evolution of superconductivity - from early conventional forms to unconventional superconductors and quantum computing” Assessment committee The Faculty of Natural Sciences has appointed the following members to the assessment committee for the evaluation of the thesis: 1st opponent: Associate Professor Søren Ulstrup Aarhus University, Denmark 2nd opponent: Professor Kazuyuki Sakamoto Osaka University, Japan Internal member: Professor Turid Renaas NTNU, Norway Professor Alireza Qaiumzadeh has been appointed Administrator of the Committee. The Committee recommends that the thesis is worthy of being publicly defended for the PhD degree. Supervisors Main supervisor : Professor Hendrik Bentmann Co-supervisor : Professor Christoph Brüne Time and venue The PhD trial lecture and defence of the thesis are open to the public: Trial lecture: 9th October 2026 at 10:15 – Disputasrommet, the Main Building, Gløshaugen, NTNU Defence of the thesis: 9 th October 2026 at 13:15 – Disputasrommet, the Main Building, Gløshaugen, NTNU Thesis summary Low-symmetry quantum materials can host unconventional electronic states originating from broken inversion symmetry, non-trivial band topology and structural chirality. Understanding these states is important both from a fundamental perspective, and for their potential to enable more energy-efficient information technologies based on spin and orbital degrees of freedom. In this thesis, angle-resolved photoemission spectroscopy (ARPES), a method that directly accesses the electronic band structure of solids, is used together with first-principles calculations to study the electronic structure of low-symmetry quantum materials. We employ spin-resolved ARPES, momentum microscopy and circular-dichroism ARPES to obtain spin- and orbital-sensitive information on the electronic structure. The first material system studied in this thesis is the Bi/Cu(111) surface alloy. Spin-resolved momentum microscopy enables a detailed mapping of polarization-dependent spin textures across its Rashba-split surface states. Next, we investigate the non-centrosymmetric Weyl semimetal PtBi2. By combining conventional and spin-resolved ARPES with first-principles calculations, we disentangled the bulk and surface electronic structure and observed spin-polarized topological Fermi arc states. These results provide a detailed picture of the electronic structure of PtBi$_2$ and contribute to the understanding of this material in light of the recently reported surface superconductivity. Finally, the structurally chiral topological semimetal CoSi is studied using circular-dichroism ARPES and one-step photoemission calculations. The results provide evidence that the structural chirality of the crystal is reflected in the orbital texture of its electronic states, demonstrating how crystal handedness can be detected through photoemission spectroscopy. Taken together, these studies demonstrate how reduced crystal symmetry gives rise to unconventional electronic states in quantum materials and highlight ARPES, combined with first-principles calculations, as a powerful tool for exploring electronic structure.

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