First-principles characterization of the electronic structure of the molecular superconductorβ−(BEDT−TTF)2IBr

Abstract

The electronic structure of the molecular superconductor ␤-(BEDT-TTF) 2 IBr 2 has been studied by means of first-principles density functional calculations. The calculated transverse cross section of the Fermi surface is in excellent agreement with that reconstructed from magnetoresistance measurements. It is shown that the cylindrical Fermi surface exhibits warping ͑the dispersion along the interlayer direction is of the order of 0.8 -1.7 % of the dispersion in the conducting plane͒ and that it does not contain any additional small pocket. These features provide support for a recent proposal concerning the much debated question of the origin of the slow magnetoresistance oscillations exhibited by this material.

Density-wave instability inα−(BEDT-TTF)2KHg(SCN)4Foury-Leylekian1, Pouget2, Lee3 et al. 2010Phys. Rev. B263340View full textAdd to dashboardCite

“…We note that we have found noticeably larger interlayer interactions ͑approxi-mately twenty five times larger͒ in similar calculations for the ␤-͑BEDT-TTF͒ 2 I 3 salt. 27 Although the general shape of the Fermi surface is the same as that found in previous extended-Hückel studies, 10,18,19 we note a neatly better quantitative agreement concerning the area of the closed portion, as it will be discussed in the next sections.…”

“…In recent years it has been increasingly clear that modern density-functional theory ͑DFT͒ approaches are reliable enough to accurately describe the electronic structure of low-dimensional molecular metals. [24][25][26][27][28][29][30] Thus, even if the calculation of the detailed Lindhard response function for a system of the structural complexity of these phases is still a computational challenge, it would provide a very important key in trying to put on a firm ground the CDW scenario.…”

Effective Coulomb interactions within BEDT-TTF dimers

“…12 Experimentally, one can tune between these phases by varying the temperature and pressure ͑including both hydrostatic and "chemical" pressure, i.e., varying the anion, X͒. 5 DFT band-structure calculations of ET crystals, [13][14][15] find a half-filled valence band and hence a metallic state. However, these calculations do not recover the Mott insulating state or the other strongly correlated effects that are observed experimentally.…”

Computing the Properties of Materials from First Principles with SIESTA

“…An extensive SIESTA study of the electronic structure for all monophosphate tungsten bronzes, (PO 2 ) 4 (WO 3 ) 2m , with known crystal structure (i.e., for m=4, 5, 6, 7, 8, 10, and 12) has also been carried out [208]. These materials are electronically more complex since the FS follows the so-called hidden nesting scenario [209], i.e., the FS results from the hybridization of three different one-dimensional FS.…”

“…Reproduced with permission from [206] origin of some conductivity anomalies of these phases [214]. Conjugate gradient structural optimizations and MD runs were used in a cooperative theoretical-experimental attempt to unravel the nature of the superstructures for phases II, III, and IV [220] as well as to discuss the relationship between the transport properties and structural details such as modifications of the host structure, hydrogen distribution and ordering among the two potential H+ intercalation sites (channels within the layers or van der Waals gaps between the layers).…”