Symmetrized mean-field description of magnetic instabilities in k-(BEDT-TTF)_2Cu[N(CN)]_2 Y salts

Abstract

We present a novel and convenient mean-field method, and apply it to study the metallic/antiferromagnetic interface of k-(BEDT-TTF)_2Cu[N(CN)]_2 Y organic superconductors (BEDT_TTF is bis-ethylen-dithio-tetrathiafulvalene, Y=Cl, Br). The method, which fully exploits the crystal symmetry, allows one to obtain the mean-field solution of the 2D Hubbard model for very large lattices, up to 6x10^5 sites, yielding a reliable description of the phase boundary in a wide region of the parameter space. The metal/antiferromagnet transtion appears to be second order, except for a narrow region of the parameter space, where the transition is very sharp and possibly first order. The cohexistence of metallic and antiferromagnetic properties is only observed for the transient state in the case of smooth second order transitions. The relevance of the present resaults to the complex experimental behavior of centrosymmetric k-phase BEDT-TTF salts is discussed.

9 pages in PS format, 7 figures (included in PS), 1 table

References in corpus (4)

• Charge Ordering in Organic ET Compounds
• Bond and charge density waves in the isotropic interacting two-dimensional quarter-filled band and the insulating state proximate to organic superconductivity
• Perturbation Theory on the Transition Temperature and Electronic Properties of Organic Superconductor
• Cyclotron effective masses in layered metals

Cited by in corpus (4)

• Evidence for structural and electronic instabilities at intermediate temperatures in $\kappa$-(BEDT-TTF)${}_2$X for X=Cu[N(CN)${}_2$]Cl, Cu[N(CN)${}_2$]Br and Cu(NCS)${}_2$: Implications for the phase diagram of these quasi-2D organic superconductors
• Towards the parameterisation of the Hubbard model for salts of BEDT-TTF: A density functional study of isolated molecules
• Effective Coulomb interactions within BEDT-TTF dimers
• Coulomb enhancement of superconducting pair-pair correlations in a $\frac{3}{4}$-filled model for $\kappa$-(BEDT-TTF)${}_2$X