Pressure effect on the topologically nontrivial electronic state and transport of lutecium monobismuthide

Rare-earth monopnictides are predicted to be nontrivial semimetal candidates and show pressure-induced superconductivity. Here, we grow LuBi single crystal and study the magnetization, transport behaviors and electronic band structures to reveal its topological semimetal feature and superconductivity under pressure. At 0 GPa, the quantum oscillations indicate that there are several topologically nontrivial carrier pockets around the Fermi level, among which the hole ones are isotropic in shape, while the electron ones are anisotropic and responsible for the angular magnetoresistance. Upon compression, the superconductivity emerges in the titled compound, showing a similar pressure dependence as that observed in LaBi. Our calculation suggests that the electronic band structures are robust at low- and high pressure, respectively, and thus the topological features are always preserved. Besides, the nearly pressure-independent density of state in LuBi indicates that the conventional electron-phonon coupling appears to play a minor role in the superconductivity.

Figure 1

(a) $T$-dependent ρ at $B_0$. The inset shows the low-T ρ and its fit to $\rho ={\rho }_0+A{T}^n$. (b) The $C_{\mathrm{p}}$ as a function of $T$ for LuBi. Inset: $C_{\mathrm{p}}/T$ vs $T$ at low $T$.

Figure 2

(a) MR data of LuBi single crystal at various $T$s. Inset: the schematic of the experiment. (b) ΔMR as a function of $B^{-1}$ at different $T$s. (c) The FFT spectra of SdH oscillations at various $T$s. Inset displays the $T$ dependence of relative FFT amplitudes of the main oscillation $F$. (d) $M$ vs $B$ for $B$//a at 2–10 K. (e) $B^{-1}$ dependence of dHvA oscillation Δ$M$. Inset displays FFT spectra of dHvA oscillations. (f) Fitting of dHvA oscillation at 2 K by the multiband LK formula.

Figure 3

(a), (b) Experimental setups for θ-dependent resistance measurement of LuBi crystal with $I$//$b$ and $B$ rotating in $ab$ and $ac$ plane, respectively. (c), (d) Polar plot of the resistance at 5 and 9 T in TLC and TC measurement models, respectively. (e) $B$ dependence of MR at various θs. (f), (g) SdH oscillation and FFT results at different θs. (h) θ dependence of $F_{\alpha }$. Solid red lines are fits to the expression $F=F_0/\cos (\theta -n\pi /2)$, with $F_0=483\mathrm{T}$ and $n=0$.

Figure 4

(a), (b) $T$ vs low-$T$ resistance at different $P$s. (c) $T_{\mathrm{sc}}\text{−}P$ phase diagram of LuBi. The upper right inset corresponds to the NaCl-type to CsCl-type structural transition. (d), (e) Low-T resistance at different $B$s, and 3.0 and 11.5 GPa, respectively. (f) $H_{\mathrm{c}}$ as a function of $T$ at 3.0 and 11.5 GPa. Solid red and blue lines are fits to the GL equation, respectively.

Figure 5

(a)–(c) Electronic band structures at 0, 3.0 and 6.6 GPa. (d) Fermi surface at 0 and 6.6 GPa. (e)–(g) Electronic band structures at 34.4, 42.1, and 53 GPa. (h) Fermi surface at 34.4 GPa.