TY - JOUR
T1 - Mott transition and phase diagram of κ-(BEDT-TTF) 2Cu(NCS) 2 studied by two-dimensional model derived from ab initio method
AU - Shinaoka, Hiroshi
AU - Misawa, Takahiro
AU - Nakamura, Kazuma
AU - Imada, Masatoshi
PY - 2012/3
Y1 - 2012/3
N2 - 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 shortranged 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 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.
AB - 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 shortranged 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 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.
KW - First principles
KW - Hubbard-type low-energy model
KW - Mott transition
KW - Organic conductors
KW - Variational Monte Carlo method
UR - http://www.scopus.com/inward/record.url?scp=84858011512&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84858011512&partnerID=8YFLogxK
U2 - 10.1143/JPSJ.81.034701
DO - 10.1143/JPSJ.81.034701
M3 - Article
AN - SCOPUS:84858011512
VL - 81
JO - Journal of the Physical Society of Japan
JF - Journal of the Physical Society of Japan
SN - 0031-9015
IS - 3
M1 - 034701
ER -