Effective Coulomb interactions within BEDT-TTF dimers

Scriven, Edan; Powell, B. J.

doi:10.1103/physrevb.80.205107

Cited by 44 publications

(55 citation statements)

References 74 publications

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“…This is also close to the estimated value of the critical ratio of U/t for the Mott transition on the triangular lattice [79]. This suggests that for J ∼ J , there is a direct transition from a spiral ordered Mott insulator to a metal as pressure is increased, which is believed to decrease U/t [3,8,80,81]. This is consistent with the observation [22] that organic charge transfer salts with t t undergo a Mott transition directly from a magnetically ordered phase to a superconducting/metallic phase, whereas salts with J /J ∼ 0.8 display spin-liquid (or other exotic quantum) phases.…”

Section: Comparison With Organicssupporting

confidence: 65%

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

2014

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We investigate the effect of ring exchange on the ground-state properties and magnetic excitations of the S = 1/2 Heisenberg model on the anisotropic triangular lattice with ring exchange at T = 0 using linear spin-wave theory. Classically, we find stable Néel, spiral and collinear magnetically ordered phases. Upon including quantum fluctuations to the model, linear spin-wave theory shows that ring exchange induces a large quantum disordered region in the phase diagram, completely wiping out the classically stable collinear phase. Analysis of the spin-wave spectra for each of these three models demonstrates that the large spin-liquid phase observed in the full model is a direct manifestation of competing classical orders. To understand the origin of these competing phases, we introduce models where either the four spin contributions from ring exchange, or the renormalization of the Heisenberg terms due to ring exchange are neglected. We find that these two terms favor rather different physics.

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Section: Comparison With Organicssupporting

confidence: 65%

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

2014

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“…[11][12][13] The magnitude of the bare "on-site" Coulomb interaction within the same molecular orbital (MO) of the benchmark TTF molecule was evaluated as ∼ 5.9 eV, which is reduced to 4.7 eV by taking into account the intra-molecular screening effects. 5 The on-site Coulomb repulsion is further reduced for larger molecules, as expected, e.g., in BEDT-TTF molecule 6,7 where it is estimated ∼4.2 eV. It is generally expected that the intra-molecular a) Author to whom correspondence should be addressed.…”

mentioning

confidence: 59%

“…5,13 The inter-molecular screening effects have also been analyzed by several approaches. [5][6][7][8]10 Multi-molecular-orbital properties have attracted recent attention in the single-component molecular solids, [14][15][16] such as [Ni(tmdt) 2 ] and [Au(tmdt) 2 ]. Among these singlecomponent molecular solids, the metallic behavior was first confirmed in [Ni(tmdt) 2 ].…”

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confidence: 99%

Ab initio derivation of multi-orbital extended Hubbard model for molecular crystals

Tsuchiizu

Omori

Suzumura

et al. 2012

The Journal of Chemical Physics

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From configuration interaction (CI) ab initio calculations, we derive an effective two-orbital extended Hubbard model based on the gerade (g) and ungerade (u) molecular orbitals (MOs) of the chargetransfer molecular conductor (TTM-TTP)I-3 and the single-component molecular conductor Au(tmdt)(2)]. First, by focusing on the isolated molecule, we determine the parameters for the model Hamiltonian so as to reproduce the CI Hamiltonian matrix. Next, we extend the analysis to two neighboring molecule pairs in the crystal and we perform similar calculations to evaluate the intermolecular interactions. From the resulting tight-binding parameters, we analyze the band structure to confirm that two bands overlap and mix in together, supporting the multi-band feature. Furthermore, using a fragment decomposition, we derive the effective model based on the fragment MOs and show that the staking TTM-TTP molecules can be described by the zig-zag two-leg ladder with the inter-molecular transfer integral being larger than the intra-fragment transfer integral within the molecule. The inter-site interactions between the fragments follow a Coulomb law, supporting the fragment decomposition strategy. . First, by focusing on the isolated molecule, we determine the parameters for the model Hamiltonian so as to reproduce the CI Hamiltonian matrix. Next, we extend the analysis to two neighboring molecule pairs in the crystal and we perform similar calculations to evaluate the intermolecular interactions. From the resulting tight-binding parameters, we analyze the band structure to confirm that two bands overlap and mix in together, supporting the multi-band feature. Furthermore, using a fragment decomposition, we derive the effective model based on the fragment MOs and show that the staking TTM-TTP molecules can be described by the zig-zag two-leg ladder with the inter-molecular transfer integral being larger than the intra-fragment transfer integral within the molecule. The inter-site interactions between the fragments follow a Coulomb law, supporting the fragment decomposition strategy.

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“…It is well known that molecular Coulomb parameters are overestimates for organic crystals; within the crystal, the interactions are strongly screened. [43][44][45] There are several promising approaches to calculating the screened Coulomb parameters, each with their own costs and benefits. 45,46 This will be addressed in a future work.…”

Section: Discussionmentioning

confidence: 99%

Electronic properties of Fabre charge-transfer salts under various temperature and pressure conditions

et al. 2013

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Using density functional theory, we determine parameters of tight-binding Hamiltonians for a variety of Fabre charge transfer salts, focusing, in particular, on the effects of temperature and pressure. Besides relying on previously published crystal structures, we experimentally determine two new sets of structures: (TMTTF) 2 SbF 6 at different temperatures and (TMTTF) 2 PF 6 under various hydrostatic pressures. We find that a few trends in the electronic behavior can be connected to the complex phase diagram shown by these materials. Decreasing temperature and increasing pressure cause the systems to become more two dimensional. We analyze the importance of correlations by considering an extended Hubbard model parameterized using Wannier orbital overlaps and show that while charge order is strongly activated by the intersite Coulomb interaction, the magnetic order is only weakly enhanced. Both orders are suppressed when the effective pressure is increased.

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Effective Coulomb interactions within BEDT-TTF dimers

Cited by 44 publications

References 74 publications

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

Ab initio derivation of multi-orbital extended Hubbard model for molecular crystals

Electronic properties of Fabre charge-transfer salts under various temperature and pressure conditions

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