laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Seminar, 19 juin 2017 (13h30 conf IV)

Arnaud Raoux (LPS, Orsay)
Orbital magnetism and geometrical aspects of band theory

Orbital magnetism of an electron gas in the periodic potential of a
crystal is an old problem that started with the discovery of orbital
diamagnetism of free electrons by Landau in 1930. Orbital magnetism is
at the origin of de Haas-van Alphen and Shubnikov-de Haas oscillations,
both surprising and very important experimental discoveries made in the
30’. Since then, lots of works have tried to generalize the Landau’s
calculations to electrons in a periodic potential. In the LPS Orsay, I
worked with G. Montambaux, F. Piéchon and J.-N. Fuchs during my PhD
thesis on that problem, and particularly to formulate the orbital
susceptibility in terms of geometry of the Hilbert space. From our
general formulation, I will give some interesing and counter-intuitive
examples of what orbital magnetism in solids can look like, mainly in
2-band models. We will see that the orbital susceptibility is intimately
linked to geometrical properties of the Bloch Hamiltonian. With this
long history, I will try to give a general view of how orbital magnetism
has been and is studied, both experimentally and theoretically.