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First publication from an experiment with the new 90-T magnet: study of Fermi surface in the superconductor FeSe

The first study using the new Toulouse 90-T magnet allowed probing the properties of the iron-based superconductor FeSe, within a collaboration between the Universities of Kyoto, Tokyo, Oxford, Birmingham, the Institute of technology of Karlsruhe, the HFML Nijmegen, and the LNCMI Toulouse, and led to a publication in Physical Review Letters. This work permitted to evidence quantum oscillations in the high-field magnetoresistivity, providing direct access to the details of the Fermi surface and showing that FeSe is a multiband system with small carriers, among them there is one small and highly mobile electron pocket. The measurements benefited from a very low electronic noise, which is similar to that offered by standard LNCMI 60 and 70-T magnets, and have been performed at a temperature of 1.4 K. Complementarily, measurements have been done using a plastic dilution fridge allowing to combine temperatures down to 100 mK to magnetic fields up to 60 T. Since this study, a new helium 3 fridge has been developed and already led to experiments at temperatures down to 500 mK combined with magnetic fields up to 90 T.

Figure : High-field magnetoresistivity of FeSe and extracted quantum oscillations and Fourier spectra.

More information :

Dichotomy between the hole and electrons behavior in the multiband FeSe probed by ultra high magnetic fields, M. D. Watson et al, Phys. Rev. Lett. 115, 027006 (2015).