Robust
Dirac-Cone Band Structure in the Molecular Kagome Compound (EDT-TTF-CONH<sub>2</sub>)<sub>6</sub>[Re<sub>6</sub>Se<sub>8</sub>(CN)<sub>6</sub>]
- Publication date
- Publisher
Abstract
(EDT-TTF-CONH<sub>2</sub>)<sub>6</sub>[Re<sub>6</sub>Se<sub>8</sub>(CN)<sub>6</sub>] is a molecular solid
with <i>R</i>3̅ space group symmetry and has the remarkable
feature of exhibiting hybrid donor layers with a kagome topology which
sustain metallic conductivity. We report a detailed study of the structural
evolution of the system as a function of temperature and pressure.
This rhombohedral phase is maintained on cooling down to 220 K or
up to 0.7 GPa pressure, beyond which a symmetry-breaking transition
to a triclinic <i>P</i>1̅ phase drives a metal to
insulator transition. Band structures calculated from the structural
data lead to a clear description of the effects of temperature and
pressure on the structural and electronic properties of this system.
Linear energy dispersion is calculated at the zero-gap Fermi level
where valence and conduction bands touch for the rhombohedral phase.
(EDT-TTF-CONH<sub>2</sub>)<sub>6</sub>[Re<sub>6</sub>Se<sub>8</sub>(CN)<sub>6</sub>] thus exhibits a regular (right circular) Dirac-cone
like that of graphene at the Fermi level, which has not been reported
previously in a molecular solid. The Dirac-cone is robust over the
stability region of the rhombohedral phase, and may result in exotic
electronic transport and optical properties