Common use of Conclusions and Discussion Clause in Contracts

Conclusions and Discussion. This work originated on the question of whether an effective gauge field would be induced by strain on the surface of a topological in- sulator. As is known this is the case in graphene which can be seen in many respects as a precursor of the actual topological insulators. It is known that elastic deforma- tions and geometrical corrugations in graphene can be de- scribed by and induced fictitious gauge field coupling to the electronic degrees of freedom [2]. The apparent para- dox that the strains do not break time reversal symmetry while magnetic fields do is solved in the graphene case by the fact that the induced fictitious field couples to the two Dirac cones with opposite signs and time reversal symme- try is preserved in the complete system. This mechanism will probably occur also in the case of weak topological insulators with an even number of Dirac cones at the sur- face. The response of a strong topological insulator to elastic deformations has to be different and remains to be studied. In this work we have seen an alternative way to generate gauge fields in a strong topological insulator and we have studied the modification of the energy spectrum caused by the gauge fields.