A Single-Component Molecular Superconductor

Abstract

The pressure dependence of the resistivities of a single-component molecular conductor, [Ni(hfdt)2] (hfdt = bis(trifluoromethyl)tetrathiafulvalenedithiolate) with semiconducting properties at ambient pressure was examined. The four-probe resistivity measurements were performed up to ∼10 GPa using a diamond anvil cell. The low-temperature insulating phase was suppressed above 7.5 GPa and the resistivity dropped, indicating the superconducting transition occurred around 7.5-8.7 GPa with a maximum Tc (onset temperature) of 5.5 K. The high-pressure crystal and electronic band structures were derived by the first-principle calculations at 6-11 GPa. The crystal was found to retain the semiconducting band structure up to 6 GPa. But the electron and hole Fermi surfaces appear at 8 GPa. These results of the calculations agree well with the observation that the pressure-induced superconducting phase of [Ni(hfdt)2] appeared just above the critical pressure where the low-temperature insulating phase was suppressed.

Pressure-Induced Conductivity in a Neutral Nonplanar Spin-Localized Radical

“…4,5 The soft nature of all these molecular crystals permits to tune their electronic properties by applying pressure which allows to switch from a semiconductor material to a metal or even a superconductor. [6][7] In view of the importance of obtaining crystals of singlecomponent molecular conductors, the use of neutral organic radicals as building blocks for molecular conductors has appeared as alternative due to the possibility that the unpaired electrons can serve as charge carriers without the need of a previous doping process. 8 Phenalenyl-based radicals, developed by Haddon,[9][10][11][12][13][14][15][16][17] and thiazolyl-based radicals, by Oakley, [18][19][20][21][22] are good examples of such materials.…”

Hydrogen-Bonding Interactions in a Single-Component Molecular Conductor: a Hydroxyethyl-Substituted Radical Gold Dithiolene Complex

“…Less investigated are the single-component molecular conductors based on bis(1,2-dithiolene) ligands. These are all neutral complexes and can be divided into two groups: those reported by Kobayashi et al where various metals (M = Ni, Co, Cu, Pd, and Au) are coordinated by two tetrathiafulvalene dithiolate ligands 5,6 and the other category in which all gold complexes are surrounded by two electron-rich dithiolene ligands. 7−10 The latter are easily generated from oxidation of the monoanionic species [Au-(dithiolene) 2 ] − .…”

Organic Semiconductors, Conductors, and Superconductors

“…Now the pressure of 200 GPa can be achieved with a diamond cell. However, the crystal is sensitive to pressure, so the experiments should be carried out carefully and slowly, step by step [112]. Bottom-up is a powerful method to obtain material with controllable designed properties.…”