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Electronic structure of a single-component molecular conductor [Pd(dddt)2] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) under high pressure

DOI: 10.7566/JPSJ.89.124706 DOI Help

Authors: Reizo Kato (RIKEN) , Hengbo Cui (RIKEN) , Takaaki Minamidate (RIKEN) , Hamish H.-m. Yeung (NIMS) , Yoshikazu Suzumura (Nagoya University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of The Physical Society Of Japan , VOL 89

State: Published (Approved)
Published: December 2020
Diamond Proposal Number(s): 20934

Abstract: We examined the high-pressure electronic structure of a single-component molecular conductor [Pd(dddt)2] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) at room temperature, on the basis of the crystal structure determined by single-crystal synchrotron X-ray diffraction measurements at 5.9 GPa. The monoclinic unit cell contains four molecules that form two crystallographically independent molecular layers. A tight-binding model of an 8 × 8 matrix Hamiltonian gives an electronic structure as a Dirac electron system. The Dirac point describes a loop within the first Brillouin zone, and a nodal line semimetal is obtained. The noticeable property of the Dirac cone with a linear dispersion is shown by calculating the density of states (DOS). The Dirac cone in this system is associated with the crossing of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) bands, which originates from the direct interaction between different molecular layers. This is a newly found mechanism in addition to the indirect interaction [J. Phys. Soc. Jpn. 86, 064705 (2017)]. The Dirac points emerge as a line when the HOMO and LUMO bands meet on the surface and the HOMO–LUMO couplings are absent. Such a mechanism is verified using a reduced model of a 4 × 4 matrix Hamiltonian. The deviation of the band energy (δE) at the Dirac point from the Fermi level is very small (δE < 0.4 meV). The nodal line is examined by calculating the parity of the occupied band eigenstates at time reversal invariant momentum (TRIM), which shows that the topological number is 1.

Subject Areas: Physics, Materials

Instruments: I19-Small Molecule Single Crystal Diffraction

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