Algebraické přístupy k elementárním excitacím v prostředích s narušenou invariancí vůči prostorové nebo časové inverzi

Erb, Kay Condie

Title: Algebraic Approaches to Elementary Excitations in Media with Broken Spatial or Time-reversal Symmetry Author: Kay Condie Erb Institute: Institute of Physics of the Czech Academy of Sciences Supervisor: Ing. Jiří Hlinka, Ph.D., Institute of Physics of the Czech Academy of Sciences Abstract: Structural phase transitions with macroscopic symmetry breaking can be divided into 212 non-magnetic species according to the mutual spatial orien- tation of the point groups of both phases. Classification into the given species implies a set of universal transition properties such as the number of macroscopic domain states of the low-symmetry phase and their distinguishability by order parameter. In this work, the distinguishability of macroscopic domain states by all order pa- rameters which transform as vectors or vectorlike quantities (called bidirectors) was studied. For solving this task, a computer algorithm was designed which enabled an explicit listing of all vector and vectorlike order parameters, not only for the 212 non-magnetic species, but even for all 1602 magnetic species which includes transitions between crystallographic gray and bicolor point groups. In addition, irreducible representations of the 122 magnetic crystallographic point groups which transform as vectors or vectorlike quantities are...

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