Optical conductivity of ABA stacked graphene trilayer : mid-IR resonance due to band nesting

The band structure and the optical conductivity of an ABA (Bernal-type) stacked graphene trilayer are calculated. It is shown that, under appropriate doping, a strong resonant peak develops in the optical conductivity, located at the frequency corresponding to approximately 1.4 times the interlayer hopping energy and caused by the 'nesting' of two nearly parabolic bands in the electronic spectrum. The intensity of this resonant absorption can be controlled by adjusting the gate voltage. The effect is robust with respect to increasing temperature.Financial support from the COMPETE Programme (FEDER) and the Portuguese Foundation for Science and Technology (FCT) through Projects PEst-C/FIS/UI0607/2013 and PTDC/FIS/113199/2009, as well as MATEPRO Project (ON2 Program) is gratefully acknowledged. ZR thanks the hospitality of the Physics Center of Minho University during her stay in Portugal. YVB, NMRP, RR and MIV acknowledge support by the EC under Graphene Flagship (contract no. CNECT-ICT-604391)

Valley and spin resonant tunneling current in ferromagnetic/nonmagnetic/ferromagnetic silicene junction

We study the transport properties in a ferromagnetic/nonmagnetic/ferromagnetic (FNF) silicene junction in which an electrostatic gate potential, U, is attached to the nonmagnetic region. We show that the electrostatic gate potential U is a useful probe to control the band structure, quasi-bound states in the nonmagnetic barrier as well as the transport properties of the FNF silicene junction. In particular, by introducing the electrostatic gate potential, both the spin and valley conductances of the junction show an oscillatory behavior. The amplitude and frequency of such oscillations can be controlled by U. As an important result, we found that by increasing U, the second characteristic of the Klein tunneling is satisfied as a result of the quasiparticles chirality which can penetrate through a potential barrier. Moreover, it is found that for special values of U, the junction shows a gap in the spin and valley-resolve conductance and the amplitude of this gap is only controlled by the on-site potential difference, Δz. Our findings of high controllability of the spin and valley transport in such a FNF silicene junction may improve the performance of nano-electronics and spintronics devices