Quantitative study of electronic whispering gallery modes in electrostatic-potential induced circular graphene junctions

Abstract

Electronic Whispering Gallery Modes (EWGMs) have been recently observed in several circular graphene junctions, pn and pp , created in scanning tunnelling microscope experiments. By computing the local density of states within the Dirac-Weyl formalism for massless fermions we demonstrate that the EWGMs may really be emerged in any type of the electrostaticpotential induced circular graphene junctions, including uni-junctions (e.g. np-or pp -junctions) as well as bipolar-junctions (e.g. pnp-heterojunctions). Surprisingly, quantitative analyses show that for all the EWGMs identified (regardless of junction types) the quality (Q) factors seem to be ≤ 10 2 , very small compared to those in ordinary optical whispering gallery modes microresonators, while the corresponding mode radii may tunably be in nanometer-scale. Our theoretical results are in good agreement with existent experimental data, putting a question to the application potential of the EWGMs identified. :1912.10691v1 [cond-mat.mes-hall] arXiv

Graphene Whisperitronics: Transducing Whispering Gallery Modes into Electronic Transport

“…Despite the constriction, the pattern is strikingly similar to the unperturbed p–n island case (see section 3 of the Supporting Information). Noteworthily, the resonant states yield LDOS patterns that extend in the low-density region (indicated by white arrows Figure d), as shown experimentally in STM in refs and and supported by recent theoretical explorations . The assignment of different m values to these LDOS extensions is made possible by explicit comparison of the tight-binding simulations shown in Figure d (obtained using the Kwant code with proper scaling as well as a homemade recursive green function code), with the exact solution of the Dirac equation (see sections 2–3 of the Supporting Information).…”

“…Noteworthily, the resonant states yield LDOS patterns that extend in the low-density region (indicated by white arrows Figure 1d), as shown experimentally in STM in refs 17 and 23 and supported by recent theoretical explorations. 24 The assignment of different m values to these LDOS extensions is made possible by explicit comparison of the tight-binding simulations shown in Figure 1d (obtained using the Kwant code 25 with proper scaling 26 as well as a homemade recursive green function code 27 ), with the exact solution of the Dirac equation 28 (see sections 2−3 of the Supporting Information). The total resistance of the WGM resonator exhibits strong oscillations versus carrier density, as shown by Figure 2b,d.…”

Graphene whisperitronics: transducing whispering gallery modes into electronic transport

“…1d), as shown experimentally in STM in Refs., 17,23 and supported by recent theoretical explorations. 24 The assignment of different m values to these LDOS extensions is made possible by explicit comparison of the tight-binding simulations shown in Fig. 1d (obtained using the Kwant code 25 with proper scaling, 26 as well as a home-made recursive green function code 27 ), with the exact solution of the Dirac equation 28 We now provide an experimental demonstration of this theoretical prediction, by generating a tunable p-n junction in a graphene device 19 using the polarized metallic tip of an atomic force microscope.…”

Nanometer-Scale Lateral p–n Junctions in Graphene/α-RuCl3 Heterostructures

“…Nanoscale lateral p–n junctions in graphene present promising routes for investigating fundamental quantum phenomena such as Andreev reflection, , whispering gallery mode resonators, , quantum dots, − Veselago lensing, , and photonic crystals . The ability to realize nanoarchitectures capable of hosting these properties relies on precise control over the lateral p–n junction size, ideally down to atomic length scales.…”