Crystal-field ground state of the noncentrosymmetric superconductor ${\text{CePt}}_3\text{Si}$: A combined polarized soft x-ray absorption and polarized neutron study

We determined the crystal-field split Hund’s rule ground state of the noncentrosymmetric heavy fermion superconductor ${\text{CePt}}_3\text{Si}$ with polarization dependent soft x-ray absorption spectroscopy (XAS) and polarized neutron scattering. We are also able to give the sequence of the crystal-field states from the temperature evolution of the linear dichroic signal in the XAS. The quantitative analysis of the XAS temperature dependence together with the neutron transition energies complete the identification of the crystal-field level scheme.

Figure 1

(Color online) Measured and simulated linear polarized XAS spectra of ${\text{CePt}}_3\text{Si}$ at the $M_{4,5}$ edges at $T=5\text{K}$. The inset shows the corresponding spatial distribution.

Figure 2

(Color online) Simulated polarizations for pure $|J_z⟩$ states of ${\text{Ce}}^{3+}$ and sum of the three polarization dependent $|J_z⟩$ spectra. The insets resemble the spatial distributions.

Figure 3

(Color online) Left panel: temperature-dependent XAS data at the $M_5$ edge. Two middle panels: simulation of spectra with ground-state wave function as determined from the 5 K XAS data and with crystal-field energies obtained from the polarized neutron data. The simulations in the middle columns have different sequences of states. Right panel: simulation with ground-state wave function and energies as given by Metoki et al. (Ref. 27).

Figure 4

(Color online) Difference of the intensities $E\perp c$ and $E\parallel c$ [linear dichroism (LD)] at peak $A$ of the $M_5$ edge versus temperature. The black dots are determined from the experimental data (left panel in Fig. 3), the dark yellow line results from a simulation according to the left, middle panel in Fig. 3.

Figure 5

(Color online) Magnetic intensities as obtained from neutron-scattering difference spectra taken at $\mathbf{Q}=\left(1.5,0,0\right)$ and $T=5\text{K}$. Open blue symbols and line: experimental data of the ${\left|M_z\right|}^2$ component and fit to the transition $|0⟩\to |1⟩$. Full red symbols: experimental data of the ${\left|M_x\right|}^2$ component, which includes the transition $|0⟩\to |1⟩$ (dotted red line, all parameters fixed, see text) as well as the transition $|0⟩\to |2⟩$ (dashed red line, all parameters free). The full red line is the sum of both contributions.