Triple-Point Fermions in Ferroelectric GeTe

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Authors	KREMPASKÝ Juraj NICOLAI Laurent GMITRA Martin CHEN Houke FANCIULLI Mauro GUEDES Eduardo B. CAPUTO Marco RADOVIĆ Milan VOLOBUEV Valentine V. CAHA Ondřej SPRINGHOLZ Gunther MINÁR Jan DIL J. Hugo
Year of publication	2021
Type	Article in Periodical
Magazine / Source	Physical Review Letters
MU Faculty or unit	Faculty of Science
Citation
Web	https://doi.org/10.1103/PhysRevLett.126.206403
Doi	http://dx.doi.org/10.1103/PhysRevLett.126.206403
Keywords	Electronic structure; Ferroelectricity; Topological phases of matter; Topological materials; Angle-resolved photoemission spectroscopy; Density functional calculations
Description	Ferroelectric alpha-GeTe is unveiled to exhibit an intriguing multiple nontrivial topology of the electronic band structure due to the existence of triple-point and type-II Weyl fermions, which goes well beyond the giant Rashba spin splitting controlled by external fields as previously reported. Using spin- and angle-resolved photoemission spectroscopy combined with ab initio density functional theory, the unique spin texture around the triple point caused by the crossing of one spin-degenerate and two spin-split bands along the ferroelectric crystal axis is derived. This consistently reveals spin winding numbers that are coupled with time-reversal symmetry and Lorentz invariance, which are found to be equal for both triple-point pairs in the Brillouin zone. The rich manifold of effects opens up promising perspectives for studying nontrivial phenomena and multicomponent fermions in condensed matter systems.
Related projects:	CEITEC Nano+ (CEITEC Nano)