High-resolution photoelectron spectroscopy study of Kondo metals: SmSn${}_3$ and Sm${}_{0.9}$La${}_{0.1}$Sn${}_3$

We performed a high-resolution photoelectron spectroscopy study on the Kondo metals SmSn${}_3$ and Sm${}_{0.9}$La${}_{0.1}$Sn${}_3$. The experimental results are compared with calculations of density of state performed within the local density approximation plus the dynamical mean-field theory. The theory is found to reproduce the experimental valence-band spectra well. In both SmSn${}_3$ and Sm${}_{0.9}$La${}_{0.1}$Sn${}_3$ the bulk Sm valence is nearly trivalent, with a small fraction of divalent component. Resonant photoelectron spectroscopy indicates a decrease in the Kondo effect in the diluted system Sm${}_{0.9}$La${}_{0.1}$Sn${}_3$.

Figure 1

Magnetic susceptibility of SmSn${}_3$ and LaSn${}_3$ at 0.1 T as a function of temperature. The solid line for SmSn${}_3$ is a fit with the modified Curie-Weiss law at $T\ge 150$ K. Inset: Schematic view of the crystal structure of SmSn${}_3$.

Figure 2

Result of the DOS calculated with LDA $+$ DMFT with a spectral line broadening of 0.01 Ry (0.136 eV) for SmSn${}_3$. (a) Total DOS. (b) Sm $4f$, $5d$, $6p$, and $6s$ partial DOS at $E_{\mathrm{b}}\le 12$ eV. (c) Sn $5d$, $5p$, and $5s$ partial DOS at $E_{\mathrm{b}}\le 12$ eV. Detailed partial DOS with a spectral line broadening of 0.001 Ry (0.0136 eV) near $E_{\mathrm{F}}$ for Sm (d) and Sn (c) at $E_{\mathrm{b}}\le 1.5$ eV. Note that in (c) and (d) the vertical scales are changed.

Figure 3

(a) Fine structure of the valence-band spectra near the Fermi level. (b) Comparison of the calculation of the DOS with the LDA $+$ DMFT approximation with a spectral line broadening of 0.01 Ry (0.136 eV; dashed line) with the measured spectrum at 136 eV for SmSn${}_3$. Detailed calculation with a spectral line broadening of 0.001 Ry (0.0136 eV; solid line) is also shown. (c) Enlargement of Fig. 3b near $E_{\mathrm{F}}$ with measured spectra of SmSn${}_3$ and Sm${}_{0.9}$Ls${}_{0.1}$Sn${}_3$ at 136 eV and 9 K with a spectrum of SmSn${}_3$ at 143 eV and 200 K.

Figure 4

(a) Temperature dependence of valence-band spectra for SmSn${}_3$ at $h\nu =16$ eV. Two distinct peaks are labeled a and b. (b) Density of states near the Fermi level.

Figure 5

(a) Resonant photoelectron spectra of the valence band for SmSn${}_3$ at $h\nu =13$–21 eV. (b) Enlargement of (a) near the Fermi level. (c) Contour intensity map as a function of incident photon energies. (d) Peak energy positions of P1 (open circles) and P2 (filled circles) as a function of incident photon energies.

Figure 6

(a) Assignment of each line and an example of the fit for the spectrum of SmSn${}_3$ at 9 K and $h\nu =143$ eV after extracting the background. (b) Enlargement of the Sm${}^{2+}$ part in (a). (c) Resonant photoelectron spectra of the valence band for SmSn${}_3$ at $h\nu =136$ and 143 eV with the off-resonant spectrum at $h\nu =125$ eV around 8.4–8.6 K. (d) Resonant photoelectron spectra of the valence band for Sm${}_{0.9}$La${}_{0.1}$Sn${}_3$ at $h\nu =136$ and 143 eV with the off-resonant spectrum at $h\nu =125$ eV at 8–9 K. (e) Comparison of the valence-band spectra between SmSn${}_3$ and Sm${}_{0.9}$La${}_{0.1}$Sn${}_3$ at $h\nu =136$ and 143 eV. (f) Enlargement of the spectra in (e) near the Fermi level.

Figure 7

(a) Valence-band spectra for SmSn${}_3$ at $h\nu =143$ eV at 9 and 100 K. (b) Valence-band spectra for Sm${}_{0.9}$La${}_{0.1}$Sn${}_3$ at $h\nu =143$ eV at 8 and 100 K.