  An increasing number of papers propose routes to implement thermal
counterparts of electronic rectification. These schemes are mainly based on
combinations of crystal anharmonicity and broken mirror symmetry. With respect
to graphene, proposals pivot around shape asymmetry induced by using
hetero-structures of nano-patterned or defected sections of pristine graphene.
Using Molecular Dynamics (MD) we show that it suffices to split a graphene
nano-ribbon into two unequal strained sections using external force which leads
to large asymmetry in the forward and reverse heat fluxes. We find that the
corresponding rectification ratio is enhanced by up to 60 %. Also, and more
importantly, the polarity is controllable on-the-fly, i.e. by changing the
position where force is applied. Based upon our results we propose a
thermo-electric device which obviates the complex nano-patterning and
lithography required to pattern graphene every time a new rectification value
or sign is sought for, opening a route to simpler fabrication and
characterization of phononic phenomena in 2D materials.
