Theoretical prediction and spectroscopic fingerprints of an orbital transition in CeCu2Si2

TL;DR

This paper predicts an orbital transition in CeCu2Si2 driven by pressure and temperature changes, with spectroscopic signatures, potentially linked to its superconducting behavior, based on advanced theoretical calculations.

Contribution

It provides a first-principles dynamical-mean-field-theory prediction of an orbital transition and its spectroscopic fingerprints in CeCu2Si2, connecting electronic structure changes to superconductivity.

Findings

Orbital transition occurs between crystal-field states under pressure and temperature changes.

Spectroscopic signatures of the transition are predicted for X-ray experiments.

The transition may be related to the second superconducting dome in CeCu2Si2.

Abstract

We show that the heavy-fermion compound CeCu2Si2 undergoes a transition between two regimes dominated by different crystal-field states. At low pressure P and low temperature T the Ce 4f electron resides in the atomic crystal-field ground state, while at high P or T the electron occupancy and spectral weight is transferred to an excited crystal-field level that hybridizes more strongly with itinerant states. These findings result from first-principles dynamical-mean-field-theory calculations. We predict experimental signatures of this orbital transition in X-ray spectroscopy. The corresponding fluctuations may be responsible for the second high-pressure superconducting dome observed in this and similar materials.