Pressure induced valence and structural transition in Ce₂Ni₃Ge₅ heavy fermion superconductor

Valence fluctuation, magnetic ordering, orbital fluctuations and crystal structure play important roles in the origin of pressure induced superconductivity in the heavy fermion materials across quantum critical point (QCP) [1]. Here we report the Ce valence and crystal structure behavior of the heavy fermion material Ce₂Ni₃Ge₅ around the proximity of superconducting regime at high pressures and low temperatures. The valence of Ce continuously increases showing an anomaly around critical pressure where superconductivity was reported, and a pressure induced structural transition from the orthorhombic to a monoclinic type of symmetry occurs above 5 GPa. The results of the Self-Interaction Correction – Local Spin Density Approximation (SIC-LSDA) theoretical calculations show the Ce 4f electrons delocalization upon compression is consistent with experiments.

Reference

[1]. Scheerer, G.W., Ren, Z., Watanabe, S. et al. The dominant role of critical valence fluctuations on high Tc superconductivity in heavy fermions. npj Quant Mater 3, 41 (2018).