Topological Bloch bands in graphene superlattices.

Bloch–Zener Oscillations in Graphene and Topological Insulators

We show that superlattices based on zero-gap semiconductors such as graphene and mercury telluride exhibit characteristic Bloch–Zener oscillations that emerge from the coherent superposition of Bloch oscillations and multiple Zener tunneling between the electron and hole branch. We demonstrate this mechanism by means of wave packet dynamics in various spatially periodically modulated nanoribbon...

Topological features and gauge fields in graphene superlattices. Detecting Topological Currents in Graphene Superlattices

The quest for crystals whose electronic bands show non trivial topological features has not ceased since the discovery of the Quantum Hall Effect. The amazing current quantization in QHE devices can be traced back to edge states which emerge from non trivial electronic structures[1, 2]. Topological properties are typically associated to integer numbers, so that they are quite robust against per...

Detecting topological currents in graphene superlattices.

Topological materials may exhibit Hall-like currents flowing transversely to the applied electric field even in the absence of a magnetic field. In graphene superlattices, which have broken inversion symmetry, topological currents originating from graphene's two valleys are predicted to flow in opposite directions and combine to produce long-range charge neutral flow. We observed this effect as...

Spin-orbit effects in a graphene bipolar pn junction

A graphene pn junction is studied theoretically in the presence of both intrinsic and Rashba spin-orbit couplings. We show that a crossover from perfect reflection to perfect transmission is achieved at normal incidence by tuning perpendicular electric field. By further studying angular dependent transmission, we demonstrate that perfect reflection at normal incidence can be clearly distinguish...

Direct measurement of the Zak phase in topological Bloch bands