Atikur Rahman, Janice Wynn Guikema, Nina Markovic
The relativistic nature of the charge carriers in graphene is manifested in the angle-dependent transmission across p-n junctions, where Klein tunneling involves annihilation of an electron and a hole at the p-n junction interface. The transmission probability is equal to unity and independent of the barrier height for normal incidence, and it oscillates as a function of barrier height for other incident angles. Here we demonstrate the angle dependence of the resistance fluctuations of ballistic dual-gated graphene devices with straight and angled arms, in which the barrier height is controlled by a shared gate electrode. We find large fluctuations in the resistance as a function of gate voltage in the case of Klein tunneling at a 45$^0$ angle, as compared to normal incidence. Using a balancing measurement technique, we isolate the angle dependence of the resistance fluctuations from other angle insensitive gate-dependent and device-dependent effects. Our results provide a direct evidence of the angle-selective transmission of charge carriers in graphene p-n junctions, which is the key element behind focusing of electrons and the realization of a Veselago lens in graphene.
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http://arxiv.org/abs/1304.5533
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