Space-group operations and time-reversal for a Dirac electron in a crystal field

It is shown in the first part how the basic formalism of the theory of spin-orbit coupling in the band theory of crystals can be deduced at once from the Dirac equation without the usual ambiguities over improper rotations associated with the formalism based on the Pauli-Schrödinger equation. In the second part it is shown that the original proofs of the time-reversal theorems given by Wigner are unnecessarily complicated.

1977 ◽  
Vol 55 (10) ◽  
pp. 937-942 ◽  
Author(s):  
A. F. Leung ◽  
Ying-Ming Poon

The absorption spectra of UCl5 single crystal were observed in the region between 0.6 and 2.4 μm at room, 77, and 4.2 K temperatures. Five pure electronic transitions were assigned at 11 665, 9772, 8950, 6643, and 4300 cm−1. The energy levels associated with these transitions were identified as the splittings of the 5f1 ground configuration under the influence of the spin–orbit coupling and a crystal field of C2v symmetry. The number of crystal field parameters was reduced by assuming the point-charge model where the positions of the ions were determined by X-ray crystallography. Then, the crystal field parameters and the spin–orbit coupling constant were calculated to be [Formula: see text],[Formula: see text], [Formula: see text], and ξ = 1760 cm−1. The vibronic analysis showed that the 90, 200, and 320 cm−1 modes were similar to the T2u(v6), T1u(v4), and T1u(v3) of an UCl6− octahedron, respectively.


2021 ◽  
Vol 103 (19) ◽  
Author(s):  
Irakli Titvinidze ◽  
Julian Legendre ◽  
Maarten Grothus ◽  
Bernhard Irsigler ◽  
Karyn Le Hur ◽  
...  

2018 ◽  
Vol 112 (7) ◽  
pp. 071903 ◽  
Author(s):  
Nicolas Chauvin ◽  
Amaury Mavel ◽  
Ali Jaffal ◽  
Gilles Patriarche ◽  
Michel Gendry

The theory of magnetic anisotropy and susceptibility of Fe 2+ in Tutton salts has been worked out on the basis of Abragam & Pryce’s method. It is found that the anisotropic part of the crystal field changes with temperature owing to the thermal expansion of the crystal lattice. The spin-orbit coupling coefficient has to be decreased by ~ 20 % from its free ion value of - 103 cm -1 which indicates some amount of overlap between the 3 d -Fe 2+ and 8 - and p -O 2- charge clouds. The agreement of the theoretical values with the experiment is good within the limitations of the approximations involved.


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