Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

摘要

The advent of Dirac materials has made it possible to realize two dimensionalgases of relativistic fermions with unprecedented transport properties incondensed matter. Their photoconductive control with ultrafast light pulses isopening new perspectives for the transmission of current and information. Herewe show that the interplay of surface and bulk transient carrier dynamics in aphotoexcited topological insulator can control an essential parameter forphotoconductivity - the balance between excess electrons and holes in the Diraccone. This can result in a strongly out of equilibrium gas of hot relativisticfermions, characterized by a surprisingly long lifetime of more than 50 ps, anda simultaneous transient shift of chemical potential by as much as 100 meV. Theunique properties of this transient Dirac cone make it possible to tune withultrafast light pulses a relativistic nanoscale Schottky barrier, in a way thatis impossible with conventional optoelectronic materials.