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Theme 3 colloquium: “Correlation meets topology: quasiparticles along the Dirac nodal loop in ZrSiS" (Lecture)

Tuesday 21 February 2017Add to my calendar
from 16:00
dr. Steffen Wiedmann (HFML)

Steffen Wiedmann-DvA-153001ZrSiS is one member of recently discovered family of topological Dirac materials whose electronic structure is believed to host Dirac-like crossing points that form a closed loop at the Fermi level [1]. Being a semi-metal with high electron mobilities, ZrSiS exhibits an extremely large magnetoresistance and low-field transport measurements have confirmed the presence of small electron and/or hole pockets via the observation of low-frequency Shubnikov-de Haas oscillations [2].

In this seminar, I will introduce the concepts of topological semi-metals and focus on magnetoresistance measurements up to 33 Tesla on high quality single crystals of ZrSiS. Above a threshold field, magnetic breakdown occurs across gaps in the loop structure with orbits that enclose different windings around its vertices, each winding accompanied by an additional π Berry phase. I will show that the amplitudes of these breakdown orbits exhibit an anomalous temperature dependence, i.e. a significant enhancement in the effective mass of the quasiparticles residing near the nodal loop. This experimental observation demonstrates the emergence of novel, correlation-driven physics associated with Dirac-like quasiparticles and opens up new frontiers for the exploration of novel exotic states in these systems [3].

[1] L. Schoop et al., Nature Commun. 7, 11696 (2016).
[2] M. Ali et al, arXiv:1603.09318 (2016).
[3] S. Pezzini et al., submitted for publication.