Comparing magnetic ground-state properties of the V- and Cr-doped topological insulator (Bi,Sb)₂Te₃

An insulating ferromagnetic ground state is a fundamental prerequisite for the quantum anomalous Hall (QAH) effect observed in magnetically doped topological insulators such as ${(\text{Bi},\mathrm{Sb})}_2{\mathrm{Te}}_3$. So far, the QAH effect could only be induced by V and Cr doping, with V resulting in ferromagnetism with a higher $T_C$ and a more robust QAH state. [...]

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Phys. Rev. B 101, 045127 (2020)

Tomonaga–Luttinger liquid in the edge channels of a quantum spin Hall insulator

Quantum spin Hall insulators are two-dimensional materials that host conducting helical electron states strictly confined to the one-dimensional boundaries. These edge channels are protected by time-reversal symmetry against single-particle backscattering, opening new avenues for spin-based electronics and computation. [...]
 

Nature Physics 16, 47-51 (2020)

Tailoring the topological surface state in ultrathin $\alpha$-Sn(111) films

We report on the electronic structure of $\alpha$-Sn films in the very low thickness regime grown on InSb(111)A. High-resolution low photon energy angle-resolved photoemission spectroscopy allows for the direct observation of the linearly dispersing two-dimensional (2D) topological surface state (TSS) that exists between the second valence band and the conduction band. [...]

Phys. Rev. B 100, 245144 (2019)

Nanophysics at surfaces

The research activities of our group are concerned with the physics of low-dimensional systems, where the electron states resulting from dimensional confinement lead to unusual conduction properties and to phase transitions as a function of temperature.

Oxide interfaces

Our group focusses on the electronic structure of correlated systems in transition metal oxides (TMOs). Special interest lies in the interplay of different degrees of freedom (charge, spin, orbital, lattice) in the light of metal-insulator and other phase transitions.

Neutron and resonant X-ray spectroscopy

In our group we investigate complex, functional materials such as transition metal oxides, which are used in the emerging field of correlated nanoelectronics. Unlike with conventional semiconductors, exotic superconducting, orbital and magnetic states can be realized at the interfaces in layered structures comprising such materials.