Continuous collapse of antiferromagnetic order toward a quantum critical point in a single-component molecular material

We uncover the pressure variation of electronic states of the single-component molecular material Pd(tmdt)2 that hosts the antiferromagnetic (AFM) Mott insulator at ambient pressure, using 13C nuclear magnetic resonance (NMR) spectroscopy. Under pressures up to 8.5 kbar, the NMR spectral broadening and the peak structure in the temperature dependence of the spin-lattice relaxation rate 1/T1 are observed and indicate that the AFM transition persists in this pressure range. However, the Neel temperature and the AFM magnetic moment are continuously decreased toward a critical pressure of similar to 9 kbar. At 10 kbar, these AFM features in the spectra and 1/T1 are suppressed, and instead 1/T1T exhibits a critical increase toward zero temperature, complying with the self-consistent renormalization (SCR) theory in two-dimensional AFM itinerant magnets [1/T1T similar to (T + theta)-1], which also explains the systematic change of 1/T1T at higher pressures. The present results indicate that Pd(tmdt)2 shows a pressure-induced quantum phase transition from the AFM Mott insulator to the paramagnetic metal at the quantum critical point of similar to 9 kbar.

Automated summary

In this study, the pressure variation of the electronic states in Pd(tmdt)2 were investigated using 13C nuclear magnetic resonance spectroscopy. The results showed a pressure-induced quantum phase transition from an antiferromagnetic Mott insulator to a paramagnetic metal at around 9 kbar.