Blurring the Boundaries Between Topological and Non-Topological Phenomena in Dots

Nov 27, 2018 - 3:30 PM -  EP06.10.04
Hynes, Level 2, Room 204
Denis Candido1,Michael Flatté2,José Carlos Egues1

Universidade de São Carlos1,The University of Iowa2
In this work we first predict using the<b> k.p</b> method and the valence band anti-crossing theory that the common III-V InAs<sub>0.85</sub>Bi<sub>0.15</sub> /AlSb quantum well becomes a room temperature 2D topological insulator for well thickness d<sub>c</sub> &lt;6.9nm. Second, we analytically solve the correspondent BHZ model for our TI by introducing a cylindrical confinement defining cylindrical quantum dots (QDs). Surprisingly, we find for the non-topological QDs “geometrically protected” discrete helical edge states, i.e., Kramers pairs with spin-angular- momentum locking, similar to the topological protected helical edge states within the gap in<br/>the topological QDs. We calculate the circulating currents associated to both trivial and topological edge states and find no substantial difference between them. The two terminal conductance calculation for two pairs of edge states as a function of the QD radius and the gate controlling its levels with respect to the Fermi energy of the leads shows a double peak at 2e<sup>2</sup>/h for both topological and trivial QDs. In conclusion, our results blur the boundaries between topological and non-topological QDs as for the protection of the helical edge states, their calculated circulating currents and their two terminal conductance measurements.