Quadrupole Fluctuation Effect on Magnetic Torque for Hourglass Dirac Loop Chain Metal β-ReO2

Magnetic torque measurements have been performed to investigate the electronic state of the metallic beta-phase ReO2 with Dirac nodal lines forming a loop chain. The sinusoidal torque curves as a function of the field angle with a two-fold symmetry are observed in the whole temperature region. The amplitude quadratically increases with field at high temperatures, which is recognized as the conventional Pauli paramagnetic behavior. As temperature decreases, the amplitude steeply increases and the nonlinear magnetization becomes evident especially for the field in the ac plane. The analyses based on Landau theory show that the change of the torque signal is ascribed to electric quadrupole fluctuations. The anisotropic susceptibility due to the quadrupole fluctuations is strongly enhanced toward 0K and 0 T, suggesting quantum critical behavior in the vicinity of a quantum critical point.

Automated summary

Magnetic torque measurements were conducted to investigate the electronic state of metallic beta-phase ReO2 with Dirac nodal lines forming a loop chain. The experimental results showed sinusoidal torque curves with a two-fold symmetry throughout the entire temperature range. As the temperature decreased, a significant nonlinear magnetization effect was observed, especially for the magnetic field in the ac plane. Analysis based on Landau theory revealed that this change in torque signal was attributed to electric quadrupole fluctuations. Furthermore, the study found a strongly enhanced anisotropic susceptibility due to quadrupole fluctuations near 0K and 0T, suggesting the presence of quantum critical behavior.