May 2011 EPL, 94 (2011) 47002 www.epljournal.org doi: 10.1209/0295-5075/94/47002 Transport response of carbon-based resonant cavities under time-dependent potential and magnetic fields C. G. Rocha 1 , M. Pacheco 2 , L. E. F. Foa Torres 3 , G. Cuniberti 1 and A. Latg´ e 4(a) 1 Institute for Materials Science and Max Bergmannn Center of Biomaterials, Dresden University of Technology D-01062 Dresden, Germany, EU 2 Departamento de F´ısica, Universidad Federico Santa Mar´ıa - Valpara´ıso, Chile 3 IFEG (CONICET) and FaMAF, Universidad Nacional de C´ ordoba, Ciudad Universitaria 5000 C´ ordoba, Argentina 4 Instituto de F´ısica, Universidade Federal Fluminense s/n - 24210-340 Niter´ oi-RJ, Brazil received 11 March 2011; accepted in final form 6 April 2011 published online 4 May 2011 PACS 72.80.Vp – Electronic transport in graphene PACS 73.23.-b – Electronic transport in mesoscopic systems Abstract – Here we report theoretical transport calculations on carbon-based nanomaterials used as resonator cavities under the effects of a time-dependent field. A magnetic field is considered as an extra modulator tool, able to encode binary ON or OFF transmission states on the quantum systems. Regular either complex conductance Fabry-P´erot patterns mapped onto gate vs. bias voltage diagrams can be revealed depending on the set of parameters used on the simulations (amplitude and frequency of the ac field and magnetic-field intensity). We discuss the interplay between the effects on the resonant cavity conductance, caused by the presence of an ac gate plate, which tends to delocalize the electronic wave functions, and an external magnetic field that oppositely localizes the electrons. Copyright c  EPLA, 2011 Introduction. – Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) have been intensively studied due to their outstanding electrical properties [1,2] that can render ultimately technological applications [3,4] such as transistors, sensors and interconnects [5,6]. In contrast to usual molecular electronics experiments revealing Coulomb blockade phenomena, the concrete ability in achieving almost transparent contacts between the carbon-based transmission channel and electrodes favors the ballistic transport. A signature of such trans- port regime is marked by the observation of regular Fabry-P´erot (FP) oscillations mapped onto gate vs. bias voltage diagrams [7]. Recent experiments [8] conducted on large CNTs (≈ 5 nm of radio and 220 nm of extension) exposed to high magnetic-field regime, indicate that FP-like conductance oscillations can be effectively modu- lated as the intensity of the field varies. Importantly, characteristic scale lengths such as the Landau radii (l B ) dictate the appearance of Landau levels in the diagrams. Whenever l B is lesser than the tube’s extension, Landau levels are generated. Moreover, magnetic fields may also (a) E-mail: latge@if.uff.br induce metal-insulator transitions in CNTs, offering an efficient way of inducing bandgap engineering at nanoscale [9–12]. Another possibility of controlling the electronic trans- mission of nanomaterials is the use of time-dependent fields [13]. Recent studies targeting the use of ac fields in carbon-based materials [14–16] shed light on this growing research area, often overshadowed by studies considering external fields in the stationary regime. Previous works have considered the effect of ac gate acting on CNTs and GNRs as a mean of achieving full control of the conduc- tance patterns [14,17]. The results have pointed to several possibilities of tuning the conductance profiles which range from suppression, phase change of the oscillations, up to robust behaviours observed even in the presence of highly intensive fields. In particular, the transport properties of the systems can be dragged towards the robustness while the driving frequency ω fulfills the stroboscopic condition: ω = nΔ, being Δ the energy level spacing of the resonant cavity, ω the ac-field frequency, and n an integer number which mimics the well-known wagon-wheel effect, now held in the quantum domain. In order to enhance the viability in incorporating such ac building-block components into 47002-p1