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Sérgio Magalhães (UFRGS) – Do multicritical points have any use to unveil novel quantum states of matter? – 8 de abril 14:00
8 de abril:14:00 - 15:00
Motivated by the unsolved problem of the nature of the Hidden Order found in URu2Si2 compound, we discuss the question proposed through our recent results (JPCM accepted (2021) and PRB 101 064207 (2020)) claiming that classical multicritical points can, indeed, be useful to understand novel quantum states of matter. We investigate the occurrence of classical multicritical points under pressure and magnetic field in a model that describes two 5f bands (of either $\alpha$ or $\beta$ characters) which hybridize with a single itinerant conduction band. The 5f-electrons interact through Coulomb and exchange terms. Three types of orderings are considered: Two conventional Spin Density Waves (SDWs) and an exotic SDW, i. e., with no magnetic moment formation. This exotic SDW is described by a purely imaginary order parameter. This phase is related to a band mixing given by the spin-flip part of the Hund’s rule exchange interaction. Our results show that the simultaneous application of pressure and field changes drastically the scenario with the suppression of some multicritical points and the emergence of others ones. We believe that these results may have relevance for the growing field of multicritical points (classical and quantum) in the physics of Uranium compounds and, perhaps, in other areas of condensed matter physics.