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Electronic properties and electronic dynamics in topological semimetals

Alberto Crepaldi

Since the discovery of topological insulators, the field of topological materials has attracted increasing attention in the condensed matter community [1]. On the one hand, the high mobility and the spin polarization of the states at the Fermi level make those compounds promising for applications. On the other hand, the low-energy electronic properties of those materials realize exotic quasiparticles, which were only postulated in high-energy physics (Dirac and Weyl Fermions) [2, 3]. Angle-resolved photoelectron spectroscopy (ARPES) has proven to be a powerful tool to directly resolve the signature of these different topological phases. In this talk I will provide a summary of my research activity of the last years. I will introduce the concept of topological semimetals, focusing on the protection and stability of the 3D Dirac semimetal phase [4-6]. By exploiting the capability of time-resolved ARPES to study the band structure upon excitation of electrons in the unoccupied conduction band, I will show you that the electron dynamics is sensitive to the formation of Weyl points [7], and that the material band dispersion can be modified by varying the electronic screening [8].

[1] M. Z. Hasan and C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010)
[2] N. P. Armitage et al., Rev. of Mod. Phys. 90, 015001 (2018)
[3] B. Bradlyn et al., Science 353, 6299 (2016)
[4] G. Manzoni et al., PRL 117, 237601 (2016)
[5] S. Roth et al., PRB 97, 165439 (2018)
[6] A. Crepaldi et al., Phys. Rev. B 95, 041408(R) (2017)
[7] A. Crepaldi et al., Phys. Rev. B 96, 241408(R) (2017)
[8] G. Gatti et al., in preparation.


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