| AVS 61st International Symposium & Exhibition | |
| 2D Materials Focus Topic | Thursday Sessions |
| Session 2D+EM+MI+MN+NS+SS+TF-ThA |
| Session: | Novel Quantum Phenomena in 2D Materials |
| Presenter: | Hugo Dil, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland |
| Correspondent: | Click to Email |
In recent years systems where the spin-orbit interaction (SOI) is not just a perturbation but the main energy scale have received increasing attention. In combination with a broken inversion symmetry in the crystal structure or at interfaces, SOI will lift the spin degeneracy and induce a complex Fermi surfaces and spin textures with spin momentum locking [1,2]. Furthermore, the SOI can drive the system through a phase transition to a so-called topological insulator. Being an insulator in the bulk these systems are characterized by spin-polarized, topologically protected interface states.
After a short introduction to the role of topology in the band structure of solids I will give an overview of our main spin- and angle-resolved photoemission (SARPES) results on a variety of non-interacting topological insulators [3]. One of the questions is how the spin texture evolves around a topological transition. We explored the occurrence of spin polarized states around a SOI driven topological transition [4] and around a structure driven topological transition [5]. In both cases we observe spin-polarized precursor states, which indicate that although the topological transition is sharp, the response of the system is more gradual.
From a fundamental point of view the truly interesting aspect of non-trivial spin textures lies in their combination with other interactions. This can result in a variety of phenomena, cumulating in the creation of the elusive Majorana Fermion. An example of a combination of interactions is our recent verification with SARPES of SmB6 as a topological Kondo insulator [6]. In topologically trivial systems, interactions can lead to the formation of a so-called spin-orbit density wave. I will show how the combination of a large spin-splitting and Fermi nesting leads to the formation of such a state and can explain the anisotropic behavior of Pb nanowires [7]. Furthermore, I will present our recent SARPES results for transition metal oxide surfaces where a subtle interplay between ferroelectricity and magnetic order results in the formation of a single spin-polarized energy contour. The occurrence of superconductivity in such systems could render it a 2D Majorana platform.[1] J.H. Dil, J. Phys: Cond. Mat. 21, 403001 (2009)
[2] G. Landolt et al. Phys. Rev, Lett. 109, 116403 (2012)
[3] D. Hsieh et al. Science 323, 919 (2009); D. Hsieh et al. Nature 460, 1101 (2009); SY. Xu et al. Science 332, 560 (2011); S. Eremeev et al. Nature Comm. 3, 635 (2012)
[4] SY. Xu et al. arXiv:1204.6518
[5] G. Landolt et al. Phys. Rev, Lett. 112, 057601 (2014)
[6] N. Xu et al. Nature Materials (2014)
[7] C. Tegenkamp et al. Phys. Rev. Lett. 109, 266401 (2012)