ABSTRACT
We have seen that the helical edge states in 2DTIs form a Kramers
doublet with the two states being related by the TRS. If a strong
external magnetic field is applied, the TRS is no longer a valid
symmetry. What happens to the helical edge states in that case?
Here we address this question, which is of both theoretical and
practical interest. The answer turns out to be quite counter-intuitive:
the helical edge states can still exist in strong quantizing magnetic
fields. The robustness of the 2DTIs is the consequence of the fact
that the edge states are bound to an effective gap domain wall that
is not destroyed by a magnetic field. However, as we shall see here,
both spectral and transport properties of the helical edge states are
modified by a strong quantizing magnetic field [67, 75, 94].