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Interplay of magnetism, Fermi surface reconstruction, and hidden-order in the heavy-fermion URu2Si2

URu2Si2 is surely one of the most mysterious of the heavy-fermion compounds. Despite more than 20 years of experimental and theoretical works, the order parameter of the transition at T0 = 17.5 K is still unknown. The state below T0 is called the “hidden-order phase,” and the stakes are still to identify the energy scales driving the system to this phase.

A new generation of magnetoresistivity and magnetization measurements on very-high-quality single crystals of URu2Si2 has been performed up to 60 T at the LNCMI-Toulouse. It permitted to show that the transition to the hidden-order state is initially driven by a high-temperature crossover at around 40–50 K, which is a fingerprint of intersite electronic correlations. In a magnetic field applied along the easy-axis c, the vanishing of this high-temperature scale precedes the polarization of the magnetic moments, as well as driving the destabilization of the hidden-order phase. Strongly impurity-dependent magnetoresistivity confirms that the Fermi surface is reconstructed below T0 and is strongly modified in a high field applied along c, i.e., at a sufficiently high magnetic polarization. These new results will help for a future understanding of the hidden-order in URu2Si2.

More information about heavy fermions can be found here

Publications :

- G. W. Scheerer, W. Knafo, D. Aoki, G. Ballon, A. Mari, D. Vignolles, and J. Flouquet, Interplay of magnetism, Fermi surface reconstructions, and hidden order in the heavy-fermion material URu2Si2, Phys. Rev. B 85, 094402 (2012).

- G. W. Scheerer, W. Knafo, D. Aoki, and J. Flouquet, Angular Dependence of the High-Magnetic-Field Phase Diagram of URu2Si2, Accepted in J. Phys. Soc. Jpn. Suppl.