Skip to main content

Trinity College Dublin, The University of Dublin

Trinity Menu Trinity Search



You are here Research > Research Groups > Nanoelectronics Theory Group > Research

Research

Recent highlights

Funding

Our work is supported by the 2D-FRUTTI Starting Laureate award from the Irish Research Council. See research.ie for more information about the council, their calls, and the essential funding they give to basic and fundamental research activities in Ireland.

Research areas

Graphene and two-dimensional materials

Two-dimensional material science has expanded rapidly since the first mechanical exfoliation of graphene in 2004. This is driven by many exciting physical, optical and electronic properties, and their associated technological applications. 2D material research now includes a range of other monolayer materials, including hexagonal boron nitride, phosphorene, silicene and the transition metal dichalcogenides. Our group uses analytic and computational methods to study the unique (and sometimes bizarre) features that arise in 2D materials. We are particularly interested in how electronic currents in 2D materials can be manipulated, but also how more exotic degrees of freedom, such as spin or valley indices, can be harnessed for future technologies.

Electronics

From a fundamental science perspective, interest in graphene is piqued by unusual electronic behaviour: a gapless and linear electronic dispersion unlike that in standard semiconductors. This leads to unexpected behaviour, such as perfect transmission through tunneling barriers (Klein tunneling) and a room temperature Quantum Hall effect. We are interested in how electronic transport in graphene is affected by both unavoidable and engineered disorders, and by interfacing with other two-dimensional materials or substrates. We use large-scale quantum transport simulations to model transport phenomena in systems such as graphene nanoribbons -- long 1D strips of graphene -- and try to explain unexpected experimental observations.

Read more (see also the publications page):

Ballistic tracks in graphene nanoribbons
J. Aprojanz, S. R. Power, et al, Nat. Commun. 9, 4426 (2018)

Conductance quantization suppression in the quantum Hall regime
J. M. Caridad, S. R. Power, et al, Nat. Commun. 9, 659 (2018)

Electron trajectories and magnetotransport in nanopatterned graphene under commensurability conditions
S. R. Power, M. R. Thomsen, et al, Phys. Rev. B 96, 075425 (2017)

Spintronics

Spintronics aims to exploit the spin of an electron to store, manipulate and transmit data for much lower energy costs than conventional electronics. However, pristine graphene is non-magnetic, so spin-up and spin-down electrons are degenerate and contribute equally to most measurements. On the other hand, graphene also has very weak spin-orbit and hyperfine interactions, suggesting the spin signals, once generated, should have a very long lifetime. Our group is interested in two possible routes toward two-dimensional spintronics: i) exploiting magnetic moments that arise at particular edges of graphene samples ii) inducing stronger spin-orbit coupling to allow conversion between charge and spin currents.

Read more (see also the publications page):

Anisotropic electronic and spin currents in nanopatterned graphene
S. S. Gregersen, J. H. Garcia, et al, J. Phys. Mater 1, 015005 (2018)

Nanostructured graphene for spintronics
S. S. Gregersen, S. R. Power, et al, Phys. Rev. B 95, 121406(R) (2017)

Indirect exchange and Ruderman–Kittel–Kasuya–Yosida (RKKY) interactions in magnetically-doped graphene
S. R. Power and M. S. Ferreira, Crystals, 3, 49-78 (2013)

Valleytronics

Valleytronics in 2D materials encodes information using the relative occupation by electrons of the K and K' (K prime) valleys at the edges of the Brillouin Zone in reciprocal space. A key obstacle is the absense of external controls, analogous to magnetic fields and ferromagnetic contacts in spintronics, to manipulate and detect valley-polarized currents. While circularly-polarized light allows optoelectronic access in certain materials, an all-electronic control is highly desirable for device applications. We have considered two possiblities to achieve this: strain-induced pseudomagnetic fields and local sublattice-dependent potentials. In both cases, we have shown that an incoming valley-neutral current can be split into K and K' polarised currents, so that such structures can be used as building blocks for more complicated valleytronic devices.

Read more (see also the publications page):

Topological Valley Currents in Graphene with Local Sublattice Asymmetry
T. Aktor, J. H. Garcia et al, arXiv:1910.00489 (2019)

Graphene nanobubbles as valley filters and beamsplitters
M. Settnes, S. R. Power, et al, Phys. Rev. Lett. 117, 276801 (2016)