Zengwei Zhu, ESPCI-LPEM

Jeudi 03 Mars 2010, 16h00
Amphi Boreau, Esc C, 2ème etage

Nernst quantum oscillations in bulk semi-metals

Zengwei ZHU
ESPCI-LPEM, 10 rue Vauquelin, 75005 Paris, France

In semi-metals a modest field of around 10T can put all electrons in their lowest Landau levels. The study of the thermoelectric response across the quantum limit reveals that the Nernst effect is a very sensitive probe of quantum oscillation phenomena[1,2]. In this presentation, I will discuss our recent measurements of Nernst effect in two elemental semi-metals, bismuth and graphite.
Comparison of thermomagnetic effects in 2D graphene with 3D graphite (a stack of graphene layers) allowed us to find that dimensionality drastically changes the profile of the Nernst response [2]. Extending our measurements on graphite up to 45 T, well above the quantum limit, we found that the Nernst response suddenly and drastically drops [3] as a consequence of a field induced phase transition previously discovered by resistivity measurements.

In the case of bismuth, the combination of a non trivial Fermi surface and strong angular dependence of the g-factor lead to a rich Landau-level spectrum. Our study of the angular- dependent Nernst effect in bismuth establishes the existence of ultraquantum field scales on top of its complex single-particle spectrum [4].

[1] K. Behnia et al., PRL, 98, 166602 (2007)
[2] Z.Zhu et al., Nature Physics, 6, 26-29 (2010)
[3] B. Fauqué, et al., to be published.
[4] H.Yang, Nature Commun., 1,41 (2010)

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