Antti-Pekka Jauho
CNG, DTU Nanotech

Graphene – and its numerous other two-dimensional cousins, hold an enormous promise for bringing along a disruptive technology. Despite of its many wonderful properties, pristine graphene has one major drawback: being a semimetal it does not have a band gap, which complicates its use in many applications. Many routes have been suggested to overcome this difficulty, such as cutting graphene into nanoribbons, using chemical methods or periodic gates, and - which is the paradigmatic example of this talk - by making regular nanoperforations, also known antidot lattices [1]. All these ideas work beautifully in theory, but realizing them in the lab is very difficult because fabrication steps inevitably induce disorder and other nonidealities, with potentially disasterous consequences for the intended device operation. In this talk I introduce these ideas and review the state-of-the –art both from the theoretical and the experimental points of view. I also introduce some new ideas, such as triangular antidots [2], and nanobubbles formed in graphene [3]. Our simulations, relying on advanced numerical techniques, predict that it may be possible to generate very high quality spin- and valley polarized currents with these structures – something that has not yet been achieved in the lab. Importantly, our simulations involve millions of atoms which is necessary in order to address structures feasible in the lab. I conclude by briefly describing the very latest (and unpublished) experimental results obtained for various nanostructured graphene samples in our lab.
[1] T. G. Pedersen et al., ”Antidot lattices: designed defects and spin qubits”, Physical Review Letters, vol. 100, 136804, April 2008
[2] S. S. Gregersen et al., ”Nanostructured graphene for spintronics”, Phys. Rev. B. vol 95, 121406(R), March 2017
[3] M. Settnes et al., ”Graphene Nanobubbles as Valley Filters and Beam Splitters”, Phys. Rev. Lett. vol. 117, 276801, December 2016