Generation of an anomalous linearly dispersing spin-polarized band in Bi-based topological insulators

Matthias Kronseder; Thomas Mayer; Jan Minár; Magdalena Marganska; Hedwig Werner; Florian Schmid; Rebeca Diaz-Pardo; Ivana Vobornik; Jun Fuji; Cornelia Streeck; Alexander Gottwald; Hendrik Kaser; Bernd Kästner; Christian H. Back

arXiv · 2605.22370

Generation of an anomalous linearly dispersing spin-polarized band in Bi-based topological insulators

Matthias Kronseder·Thomas Mayer·Jan Minár·Magdalena Marganska·Hedwig Werner·Florian Schmid·Rebeca Diaz-Pardo·Ivana Vobornik·Jun Fuji·Cornelia Streeck·Alexander Gottwald·Hendrik Kaser·Bernd Kästner·Christian H. Back

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Abstract

We report the generation of an anomalous linearly dispersing, spin-polarized band in Bi-based topological insulator (TI) thin films, induced by soft Ar-ion bombardment followed by annealing. This extra band -- which we call the anomalous linearly dispersing state (ALS) -- is superimposed on the regular band structure including the topological surface state (TSS), spans an unusually large energetic range of up to ${\sim}\,\SI{650}{\milli\electronvolt}$ at the $Γ$-point, and appears near the Fermi energy. Spin-resolved measurements indicate spin-momentum locking with a helicity \emph{opposite} to that of the regular TSS. The Fermi velocity of the ALS, $v_\mathrm{F} = (5.1\pm 0.4)\times 10^{5}\,\frac m s$, is indistinguishable from that of the regular TSS, $(5.3\pm 0.5)\times 10^{5}\,\frac m s$. The observation is reproducible across samples of varying thickness and was confirmed at two independent synchrotron radiation facilities. We discuss different mechanisms for the physical origin of the observed ALS including sputtering-induced TSS relocation, bi-layer formation by,e.g., chalcogen removal, and high-index surface relocation.

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Matthias Kronseder, Thomas Mayer, Jan Minár, Magdalena Marganska, Hedwig Werner, Florian Schmid, Rebeca Diaz-Pardo, Ivana Vobornik, Jun Fuji, Cornelia Streeck, Alexander Gottwald, Hendrik Kaser, Bernd Kästner, Christian H. Back. 2026-05-21. Generation of an anomalous linearly dispersing spin-polarized band in Bi-based topological insulators. https://arxiv.org/abs/2605.22370

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