New answers tagged topological-insulators
Just to give a rough intuitive explanation as to why we want to look at loops. Time-reversal symmetry is roughly complex conjugation, so we want to know if this matrix elements are non-real. However, just by redefining the electron creation operators $a_R \rightarrow a_Rexp(i\theta)$ I can change the phases of the hopping matrix elements, which is just gauge ...
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