Electronic structure of θ-(BEDT-TTF) 2 RbZn(SCN) 4 above the metal to insulator phase transition. (a) Calculated band structure using the 220 K crystal structure. (b) Calculated band structure for θ-(BEDT-TTF) 2 RbZn(SCN) 4 using the same crystal structure and a double cell × × a b c 2. The result of the full calculation is shown in red whereas the result of a calculation where the anions were completely removed and replaced by a uniform background of charge is shown in blue. The energy zero corresponds to the Fermi level. ( ) Γ = 0, 0, 0 , X = (1/2, 0, 0), Z = (0, 0, 1/2) and M = (1/2, 0, 1/2) in units of the orthorhombic reciprocal lattice vectors. (c) Calculated = b* 0.0 section of the Fermi surface. 

Contexts in source publication

Context 1

... calculated band structure near the Fermi level for the 220 K structure of θ-(Rb,Zn) (i.e. above the phase transition) is shown in figure 4(a). The two bands are almost exclusively built from the HOMO of BEDT-TTF and because of the stoi- chiometry, they contain one hole so that the upper band is half-filled. ...

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... that because of the symmetry equivalence of the two layers, the bands of figure 4(a) are really the super- position of two identical bands. The = b* 0.0 section of the calculated Fermi surface is shown in figure 4(c). The disper- sion along the interlayer direction is very small (less than 1 meV) so that the 3D Fermi surface practically does not exhibit warping along this direction. ...

Context 3

... order to facilitate the comparison with the electronic structure below the metal to insulator transition we show in figure 4(b) the band structure folded along the c* direction. To consider the possible role of the anion Hartree potential in the transition we have also calculated the electronic struc- ture using exactly the same computational details as before, but replacing the anions by a uniform background charge amounting to two electrons per unit cell (i.e. one per layer) so as to keep the electroneutrality of the system. ...

Context 4

... consider the possible role of the anion Hartree potential in the transition we have also calculated the electronic struc- ture using exactly the same computational details as before, but replacing the anions by a uniform background charge amounting to two electrons per unit cell (i.e. one per layer) so as to keep the electroneutrality of the system. As shown in figure 4(b) practically nothing changes between the two calcu- lations, especially around the Fermi level and, consequently, the two Fermi surfaces are also practically indistinguishable. We thus conclude that the anions mostly influence the elec- tronic structure through the deformations induced in the donor lattice and not in a direct way through their Hartree potential. ...

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... a classical Peierls-like mechanism does not seem to be appropriate to rationalize the pressure induced changes in the θ-(Cs, Co) salt. In the same vein, let us remark that from the three ambient pressure salts showing a relatively high temper- ature metal to insulator transition associated with the appear- ance of a q 2 = (0, 0, 1/2) modulation, one of them (θ-(Rb, Zn), see figure 4(c)) shows the ellipse-like Fermi surface of figure 6(a) whereas the other two show that of figure 6(b). We conclude that a classical Peierls-like mechanism is not appro- priate for these salts (see below) and that the interactions along the stacks (t c ) play the major role in differentiating the phase diagram of the θ phases. ...

Context 6

... the metal to insulator phase transition) of θ-(Rb,Zn) is shown in figure 8(a). Comparing this band structure with the c-folded one of the system above the transition (see figure 4(b)) makes it clear that the changes brought about are very substantial, specially around the Fermi level. Most noticeably, there is a strong degeneracy loss at the M' and Z' (upper band) points of the Brillouin zone (BZ) associated with the loss of the 2 1 screw axis along c. ...