High-Pressure Crystal Structure and Unusual Magnetoresistance of a Single-Component Molecular Conductor [Pd(dddt)2] (dddt=5,6-dihydro-1,4-dithiin-2,3-dithiolate)

A single-component molecular crystal [Pd(dddt)(2)] has been shown to exhibit almost temperature-independent resistivity under high pressure, leading theoretical studies to propose it as a three-dimensional (3D) Dirac electron system. To obtain more experimental information about the high-pressure electronic states, detailed resistivity measurements were performed, which show temperature-independent behavior at 13 GPa and then an upturn in the low temperature region at higher pressures. High-pressure single-crystal structure analysis was also performed for the first time, revealing the presence of pressure-induced structural disorder, which is possibly related to the changes in resistivity in the higher-pressure region. Calculations based on the disordered structure reveal that the Dirac cone state and semiconducting state coexist, indicating that the electronic state at high pressure is not a simple Dirac electron system as previously believed. Finally, the first measurements of magnetoresistance on [Pd(dddt)(2)] under high pressure are reported, revealing unusual behavior that seems to originate from the Dirac electron state.

Automated summary

A single-component molecular crystal [Pd(dddt)(2)] has been found to exhibit unique resistivity behavior under high pressure, with high-pressure single-crystal structure analysis revealing pressure-induced structural disorder. Calculations show that the electronic state at high pressure is more complex than previously thought. Magnetoresistance measurements under high pressure suggest unusual behavior originating from the Dirac electron state.