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Séminaire MCBT

Mardi 5 Décembre à 11h00,
Salle Louis Weil E424

Oratrice : Emilie TISSEROND (LPS-Orsay)
"Aperiodic quantum oscillations of particle­-hole asymmetric Dirac cones"


Most of the materials studied in condensed matter physics are composed of massive fermions which verify usual parabolic dispersion relations. Since the 2000s, with the discovery of the graphene, we have witnessed the emergence of new materials having a linear dispersion relation : the Dirac materials. It is the case of the a(BEDT­TTF)2I3 organic metal (afterward, denoted aI3), under high hydrostatic pressure (P>1,5GPa) [1]. In contrast to the case of purely 2D graphene on SiO2, the 3D bulk structure of aI3 allows to probe a much closer to the Dirac point physics. However, the coexistence of massive and Dirac fermions within the aI3 compound [2] makes this study particularly complex, albeit richer and surprising. The Shubnikov­­ de Haas oscillations (semi­classical oscillations of the magnetoresistance) in al3, under high pressures and very low temperatures (about 2GPa and 200 mK), reveal anomalies. Indeed, although the periodic behavior in 1/B of these oscillations at low magnetic fields is well known and understood, it is not the case for the deviation from this behavior, which appears at higher magnetic fields (B>7T). This kind of particular behavior has very recently been observed for surface states of 3D topological insulators samples [3], however the effect is much stronger in aI3. We interpret these unusual results with an original theoretical model that takes into account intrinsic distortions of the aI3 Dirac cones such as a parabolic particle­-hole asymmetric correction. The observations are consistent among aI3 different Fermi levels [4].

[1] Kobayashi A., Katayama S., Suzumura Y., and Fukuyama H., J. Phys. Soc. Jpn., 76 034711 (2007)
[2] Monteverde M., Goerbig M. O., Auban­Senzier P., Navarin F., Henck H., Pasquier C. R., Mézière C. and Batail P., Phys. Rev. B., 87 245110 (2013)
[3] Wright A. R. and McKenzie R. H., Phys. Rev. B., 87 085411 (2013)
[4] arXiv:1711.00039 [cond­mat.mes­hall] (2017)

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