Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 4: Transport: Topological Insulators 1 (jointly with HL and MA)

TT 4.8: Vortrag

Montag, 26. März 2012, 11:30–11:45, H 3010

Weak antilocalization in HgTe quantum wells and topological surface states: Massive versus massless Dirac fermions — •Ewelina Hankiewicz and Grigory Tkachov — Wuerzburg University

HgTe quantum wells and surfaces of three-dimensional topological insulators support Dirac fermions with a single-valley band dispersion. In this work we conduct a comparative theoretical study of the weak antilocalization in HgTe quantum wells (QWs) and topological surface states. The difference between these two single-valley systems comes from a finite band gap (effective Dirac mass) in HgTe quantum wells in contrast to gapless (massless) surface states in topological insulators. The finite effective Dirac mass implies a broken internal symmetry, leading to suppression of the weak antilocalization in HgTe quantum wells and transition to the weak localization regime as a function of the gap or carrier density. Further we show how the difference in the behavior of the weak localization corrections for HgTe QWs allows to distinguish topological versus normal insulators. On the other hand, the topological surface states exhibit specific weak-antilocalization magnetoconductivity in a parallel magnetic field due to their exponential decay in the bulk. The relevant experiments will be discussed.

We acknowledge the financial support of the German DFG Grant HA5893/1-2 .