Specific heat and NMR evidence for the low Fermi-level density of states in semimetallic ScSb

We report the electronic and thermal properties of scandium monoantimonide ScSb by means of the Seebeck coefficient, thermal conductivity, specific heat, and nuclear magnetic resonance measurements. The experimental Seebeck coefficient exhibits a strong temperature dependence, and the theoretical calculation based on the two-band model provides a realistic description of the observed feature. The analysis of the thermal conductivity reveals that the lattice thermal conductivity dominates at low temperatures while electronic thermal conductivity makes a major contribution at high temperatures. A small value of the Sommerfeld coefficient of $0.38\mathrm{mJ}\mathrm{mo}{\mathrm{l}}^{\text{–}1}{\mathrm{K}}^{\text{–}2}$ was extracted from the low-temperature specific heat measurement, indicative of a low electronic Fermi-level density of states (DOS) in ScSb. Furthermore, we have deduced the Sc $3d$ and Sb $5s$ partial Fermi-level DOSs based on the Korringa behavior in the ${}^{45}\mathrm{Sc}$ and ${}^{121}\mathrm{Sb}$ NMR spin-lattice relaxation rates. The determined values of the DOS are quite low, giving strong evidence for the semimetallic character in ScSb.

Figure 1

Single-crystal x-ray diffraction of the ($l00$) planes measured at room temperature. The insets show a photograph of the single-crystalline ScSb and the corresponding crystal structure.

Figure 2

Temperature dependence of the experimental and calculated total Seebeck coefficients of ScSb. The calculated partial Seebeck coefficients of holes ($S_h$) and electrons ($S_e$) as a function of temperature are displayed.

Figure 3

Temperature variation of the thermal conductivity κ of ScSb. The decomposed electronic and lattice thermal conductivity are presented by circle and cross symbols, respectively. The solid curve represents the fitting result of the lattice thermal conductivity using Eqs. (1) and (2).

Figure 4

Temperature dependence of the specific heat $C_p$ of ScSb between 1.8 and 10 K. The upper inset is a plot of $C_p/T$ vs $T^2$, in which the solid line is a fit to the experimental data according to $C_p/T=\gamma +\beta T^2$ between 1.8 and 7.6 K. The lower inset shows the high-temperature specific heat data with a fitting curve according to Eq. (3).

Figure 5

${}^{45}\mathrm{Sc}$ and ${}^{121}\mathrm{Sb}$ NMR central transition spectra of ScSb measured at 77 and 300 K. The dotted and dashed lines denote the positions of the ${}^{45}\mathrm{Sc}$ and ${}^{121}\mathrm{Sb}$ NMR reference frequency, respectively.

Figure 6

(a) Temperature dependence of the ${}^{45}\mathrm{Sc}$ spin-lattice relaxation rate ${}^{45}\left(1/T_1\right)$ of ScSb. (b) Temperature variation of the ${}^{121}\mathrm{Sb}$ spin-lattice relaxation rate ${}^{121}\left(1/T_1\right)$ of ScSb. Each dashed line indicates the Korringa behavior for the relaxation rates.