Possible pressure-induced topological quantum phase transition in the nodal line semimetal ZrSiS

ZrSiS has recently gained attention due to its unusual electronic properties: nearly perfect electron-hole compensation, large, anisotropic magnetoresistance, multiple Dirac nodes near the Fermi level, and an extremely large range of linear dispersion of up to $\sim 2$ eV. We carried out a series of high pressure electrical resistivity measurements on single crystals of ZrSiS. Shubnikov-de Haas measurements show two distinct oscillation frequencies. For the smaller orbit, we observe a change in the phase of $\sim 0.5$, which occurs between $0.16–0.5$ GPa. This change in phase is accompanied by an abrupt decrease of the cross-sectional area of this Fermi surface. We attribute this change in phase to a possible topological quantum phase transition. The phase of the larger orbit exhibits a Berry phase of $\pi$ and remains roughly constant up to $\sim 2.3$ GPa. Resistivity measurements to higher pressures show no evidence for pressure-induced superconductivity to at least $\sim 20$ GPa.

Figure 1

(a) Resistivity vs temperature, (b) resistivity vs magnetic field measured at 2 K, and (c) oscillatory part of the resistivity vs magnetic field at various pressures for sample 8 measured at 2 K. The data have been vertically offset for clarity. The magnetic field was applied parallel to the crystallographic c-axis. Fermi surface parameters derived from analyzing this and other data are presented in Fig. 2.

Figure 2

(Left) Several Fermi surface parameters of ZrSiS at 2 K as a function of pressure for the smaller Fermi surface, with an oscillation frequency $F_1$. (a) Landau level fan diagram with selected pressures from sample 8. (b) Oscillation frequency $F_1$ for all samples as a function of pressure, (c) $n$-intercept, $n_0$, of the LL fan diagram of $F_1$. This Fermi surface is known to be 3D and fairly isotropic. The intercept $n_0$ discontinuously drops by $\sim 0.47$ between 0.16–0.5 GPa, which could suggest that the Berry phase of this orbit changes by a factor of $\pi$. The dotted lines indicate the average values of $n_0$ below and above the transition pressure, which are 0.66 and 0.19, respectively. The nature of this change in phase is discussed in more detail in the text. (Right) Several Fermi surface parameters of ZrSiS at 2 K as a function of pressure for the larger Fermi surface, with frequency $F_2$. (d) Landau level fan diagram with selected pressures from sample 8. (e) Oscillation frequency $F_2$ for all samples as a function of pressure, (f) $n$-intercept of the LL fan diagram of the larger orbit, which exhibits a Berry phase of $\pi$ and stays roughly constant.

Figure 3

Electrical resistivity of ZrSiS in the $ab$-plane as a function of applied pressure for samples 5 and 6. Clear changes in the slope of $\rho$ vs P occur between $11–14.5$ GPa. Pressure was released at $\sim 1.8$ K for sample 5.