Alexander Holleitner Tuesday, 10:40 - 11:10
Symmetry breaking and ultrafast helicity-dependent currents in topological insulators
Three-dimensional topological insulators constitute a fascinating class of materials with a strong spin-orbit coupling exhibiting non-trivial, gapless states on the surface and insulating bulk states.(1)-(4) In revealing the optoelectronic dynamics in the whole range from femto- to microseconds, we demonstrate that the long surface lifetime of Bi2Te2Se-nanowires allows to access the respective surface states by a pulsed photoconduction scheme even at room temperature.(5) Moreover, we highlight how to access ultrafast helicity-dependent surface currents in the topological insulators within the spin-relaxation lifetime of the investigated topological insulators.(2,4)
In a second part, we show that the symmetry of helicity-dependent photocurrents in Bi2Te2Se-nanowires can be broken by extrinsic and intrinsic anisotropies within the circuits.(6,7) Our results open the avenue for two-dimensional, topological materials as active modules in optoelectronic high-frequency and on-chip THz-circuits.(4)

We acknowledge financial support by the ERC grant NanoREAL and the DFG priority program SPP1666 on “topological insulators”.

(1) J. W. McIver, et al. Nature Nano 7, 96 (2012).
(2) C. Kastl, et al. Nature Comm. 6, 6617 (2015).
(3) C. Kastl, et al. 2D Materials 2, 024012 (2015).
(4) C. Kastl, et al. IEEE J. Sel. Topics Quantum Electron. 23, 8700305 (2017).
(5) P. Seifert, et al. Nano Letters 17, 973 (2017).
(6) P. Seifert, et al. Symmetry and topology concepts accepted (2017).
(7) P. Seifert, et al. (2017).