2D Fermi Surface of BEDT

As already discussed, each layer of BEDT-TTF molecules in κ-(BEDT-TTF)2Cu(NCS)2 is parallel to the crystallographic bc-plane. In the CAESAR\Examples\Chapter8\ET directory, the BC, PC and FI input files for an isolated donor-molecule layer are D.BI, D.PI and D.FI, respectively. The following figure shows the Fermi surfaces in an extended zone. To obtain this picture, it was necessary (1) to change the labels of symmetry points by using the Unit cell box command of the Preference menu and then selecting the item yz(2D) to switch the symmetry labels from 'X' and 'Y' to 'Y' and 'Z', respectively, (2) to use the Zoom command and select the option Zoom Out 25% to reduce its size, and (3) then to click the 5x5 command of the Extend menu.

The Fermi surfaces of κ-(BEDT-TTF)2Cu(NCS)2 in the figure are essentially described as overlapping distorted circles and these circles split into wavy lines and small elongated ellipses due to a noncrossing at the intended crossing points, which reflect that this salt has two non-equivalent BEDT-TTF molecules. More explicitly, the Fermi surface of κ-(BEDT-TTF)2Cu(NCS)2 contains the hole surface and the electron surface, which are respectively associated with the lower and upper subbands of the highest occupied band.

BEDT Fermi

Figure. Fermi surfaces of κ-(BEDT-TTF)2Cu(NCS)2 in an extended zone.

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