2011/10/31 by Hiroshi Shinaoka, Takahiro Misawa, Kazuma Nakamura +1
Materials Science · Physics and Astronomy · #2D Materials and Applications #Iron-based superconductors research #Organic and Molecular Conductors Research #cond-mat.str-el
paper · pdf · doi:10.1143/jpsj.81.034701
published as J. Phys. Soc. Jpn. 81, 034701(1-12) (2012) · 15 pages, 11 figures (minor revision, to appear in JPSJ)
arxiv created 2012/02/08 · openalex publication_date 2012/02/14 · arxiv updated 2012/03/09 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We present an ab initio analysis for the ground-state properties of a correlated organic compound κ-(BEDT-TTF)2Cu(NCS)2. First, we derive an effective two-dimensional low-energy model from first principles, having short-ranged transfers and short-ranged Coulomb and exchange interactions. Then, we perform many-variable variational Monte Carlo calculations for this model and draw a ground-state phase diagram as functions of scaling parameters for the onsite and off-site interactions. The phase diagram consists of three phases; a paramagnetic metallic phase, an antiferromagnetic (Mott) insulating phase, and a charge-ordered insulating phase. In the phase diagram, the parameters for the real compound are close to the first-order Mott transition, being consistent with experiments. We show that the off-site Coulomb and exchange interactions affect the phase boundary; (i) they appreciably stabilize the metallic state against the Mott insulating phase and (ii) enhance charge fluctuations in a wide parameter region in the metallic phase. We observe arc-like structure in Fermi surface around the region where the charge fluctuations are enhanced. Possible relevance of the charge fluctuations to the experimentally observed dielectric anomaly in the κ-BEDT-TTF family compounds is also pointed out.