Dr Sharon Strawbridge
Senior Lecturer (Education and Scholarship)
Telephone: 01392 725189
Extension: (Streatham) 5189
Research interests: Graphene and related 2D materials
My main areas of interest are both related by a very interesting property that both single layer graphene and strong topological insulators have in common, the exsistence of a gapless linear electronic energy dispersion (Dirac cone/s). This leads to, at the intersection of the valence and conduction bands, the presence of massless electrons (fermions), which can propagate in the relativistic regime (300/c) described by the Dirac equation. In purely 2D graphene this property has been intensively investigated theoretically and experimentally, as have the other exceptional properties of this atomically thin material, culminating in the award of the 2010 Nobel prize to Andre Geim and Konstantin Novoselov (Manchester) for their pioneeering work on graphene.
Work on graphene started in Exeter very shortly after the seminal papers came out from Manchester. The Centre for Graphene Science has allowed Exeter and Bath universities colaborate on graphene research and represents one of the largest groups in the UK working on graphene science.
I am interested both in the fundamental properties of graphene and the application of these properties in real devices.
Topological states of matter are becoming a very "hot" topic in theoretical physics with a large number of papers having been published in the last 2-3 years, with experimental work just starting to be undertaken. this is a new area that is moving rapidly. My interests in topological insulators (TIs) has developed directly from my interests in graphene.
In graphene the Dirac fermions propagate over the 2D surface of the crystal, however, in the case of 3D topological insulators, the bulk of the crystal is insulating and the massless fermions are only present on the very surface of the crystal. TIs such as bismuth teluride can be cleaved mechanically in a similar way to graphite to produce ultra-thin sheets, in the case of these very thin layer (psuedo 2D) TIs, the massless fermions propagate at the edges of the sample. The Dirac fermions in strong topological insulators such as bismuth teluride possess a curious property resulting from strong spin orbit coupling (SOC) known as the quantum spin Hall effect (QSHE) analogous to the quantum Hall effect (QHE), where the electron spins are separated at the edge/surface of the crystal without the presence of an external magnetic field due to the time reversal symmetry of the system (i.e topology). This effect could potentially be exploited to produce pure spin polarised currents. The development and control of pure spin polarised currents will be of huge technological importance leading to spin based electronic applications.
I am interested in developing practical devices exploiting the remarkable properties of Dirac systems and understanding the behaviour of these systems. The specific areas of activity and interest are listed below:
Molecular doping of graphene (see publications)
Graphene based sensors
Development of carbon based electronics
Theoretical background of new Dirac systems
Bi2Te3(Se3) methodologies for synthesis and device fabrication
Topological insulator based spintronic devices