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Séminaire MCBT

Mardi 9 octobre à 11h00,
Salle Louis Weil, E424

Orateur : Matthias Raba (LNCMI/Institut Néel)
"Electronic and magnetic properties of CePt2In7"


The appearance of unconventional superconductivity in the vicinity of a quantum critical point (QCP), a second order phase transition at zero temperature, is a common trend in Ce-based heavy fermion compounds. A more recent and still somewhat controversial issue is the effect of the Fermi surface (FS) dimensionality on this superconductivity. Indeed, reduced dimensionality of the FS leads to nesting-type magnetic instabilities and thus enhances the superconductivity. The exact knowledge of the FS topology of heavy fermion systems is, therefore, essential. In addition, this information allows distinguishing if the f-electrons are itinerant or localized, i.e. whether they contribute to the FS or not.

At ambient pressure and zero magnetic field, the heavy-fermion compound CePt2In7 exhibits an antiferromagnetic (AFM) phase below 5.5 K. The AFM order is suppressed at a pressure-induced QCP at Pc = 3.2 GPa [1], around which a superconducting dome emerges. A magnetic-field-induced QCP is also expected at Hc 55 T [2]. The 4f-electrons of Ce are known to be fully localized at ambient pressure and moderate magnetic fields [3]. However, the question of whether the f-electrons are itinerant or localized above the QCPs is still open due to the lack of quantum oscillation studies either at high pressure or high magnetic field.

Our recent results of quantum oscillation measurements in pulsed magnetic fields suggest that the FSs do not change up to 70 T, which is well above the field induced QCP. However, the effective mass is found to drop suddenly at 47 T, where a clear anomaly is observed in magnetic torque. This anomaly is almost angle and temperature independent [4]. We argue that the anomaly is due to a valence crossover [5]. I will also present first quantum oscillation measurements under pressure, which will allow us to probe the FSs across Pc.

[1] V. A. Sidorov et al., Phys. Rev. B 88, 020503(R) (2013)
[2] Y. Krupko et al., Phys. Rev. B 93, 085121 (2016)
[3] K. Götze et al., Phys. Rev. B 96, 075138 (2017)
[4] M. M. Altarawneh et al., Phys. Rev. B 81, 081103(R) (2011)
[5] S. Watanabe et al., J. Phys. : Cond. Mat. 23, 094217 (2011)

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