Possible multiorbital ground state in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>CeCu</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>Si</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math>
Andrea Amorese, Andrea Marino, Martin Sundermann, Kai Chen, Zhiwei Hu, Thomas Willers, Fadi Choueikani, Philippe Ohresser, Javier Herrero‐Martín, Stefano Agrestini, Chien‐Te Chen, Hong‐Ji Lin, M. W. Haverkort, S. Seiro, C. Geibel, F. Steglich, L. H. Tjeng, Gertrud Zwicknagl, A. Severing
Abstract
The heavy-fermion superconductor CeCu${}_{2}$Si${}_{2}$ is investigated with soft x-ray absorption spectroscopy in the temperature range from 250 mK to 250 K and the ${J}_{z}$ admixture of the ${\mathrm{\ensuremath{\Gamma}}}_{7}$ ground-state wave function is determined. The overall temperature dependence of the experimental linear dichroism is reproduced well by the thermal occupation of excited crystal-field states so that the scenario of orbital switching seems unlikely. Spectroscopic evidence for the presence of the Ce 4${f}^{0}$ configuration in the ground state is consistent with the possibility of a multiorbital character of the ground state.