Effect of energy band gap in graphene on negative refraction through the veselago lens and electron conductance

Abstract

A remarkable property of intrinsic graphene is that upon doping, electrons and holes travel through the monolayer thick material with constant velocity which does not depend on energy up to about 0.3 eV (Dirac fermions), as though the electrons and holes are massless particles and antiparticles which move at the Fermi velocity vF . Consequently, there is Klein tunneling at a p − n junction, in which there is no backscattering at normal incidence of massless Dirac fermions. However, this process yielding perfect transmission at normal incidence is expected to be affected when the group velocity of the charge carriers is energy dependent and there is non-zero effective mass for the target particle. We investigate how away from normal incidence the combined effect of incident electron energy and band gap parameter ∆ can determine whether a p − n junction would allow focusing of an electron beam by behaving like a Veselago lens with negative refractive index. We demonstrate that there is a specific region in − ∆ space where the index of refraction is negative, i.e., where monolayer graphene behaves as a metamaterial. Outside this region, the refractive index may be positive or there may be no refraction at all. We compute the ballistic conductance across a p − n junction as a function of ∆ and and compare our results with those for a single electrostatic potential barrier and multiple barriers.

Properties of Gaussian Beam Propagating in Ring Resonator Sensor

“…To the best of our knowledge, this ring resonator sensor can probe other solutions like sucrose, Na 2 CO 3 , and so on in so far as the parameters of intercept and slope of (19) and (20) are adjusted. It is expected that the proposed ring resonator sensor and the corresponding conclusions can be useful for precise optical measurement, especially for food safety inspection and medical services of health care.…”

“…Meanwhile, we propose a ring resonator sensor to measure the concentration of NaCl, whose operating principle, especially the influence of the concave mirror curvature radius on the emerging beam evolution, is deliberatively analyzed. The functional relation between normalized central intensity, beam spot size, and NaCl solution concentration is given by (19) and (20), respectively, and assuredly reaches high precision and linearity. It is expected that the proposed ring resonator sensor and the corresponding conclusions can be useful for precise optical measurement, especially for food safety inspection and medical services of health care.…”

“…In addition, there are single negative materials (SNMs) among which only one of the EM parameters is negative; these materials include the epsilon negative media (ENGM, < 0, > 0) and the mu negative media (MNGM, > 0, < 0) [16,17]. NIMs have many markedly novel phenomena, for instance, large negative lateral shift [18], beam focusing and phase compensation [19], negative refraction EM energy [20], reverse Doppler Effect [21], inverse Cerenkov radiation [22], etc. These novel characteristics are widely employed in designing periodic-structure like the photonic crystal [23] and optical thin film coating [24].…”

Interplay between effects of barrier tilting and scatterers within a barrier on tunneling transport of Dirac electrons in graphene

“…Other significant roles played by our proposed tunable junctions include Veselago lens 19,20 by exploiting optics-like behavior of ballistic Dirac electrons, Fabry-Perot interferometer, 13 subthermal switches, 5 and Andreev reflections 21 . Therefore, in order to design next-generation graphene-based electronics, it is crucial to gain a full understanding of physics mechanism for ballistic transports across various types of potential barriers in graphene.…”

Adatom doping-enriched geometric and electronic properties of pristine graphene: a method to modify the band gap

“…Creating pristine graphene in commercial quantities with a specific band gap is a major challenge in its use for nanoelectronic devices. Some of the intriguing properties which have received a great deal of attention include the doping and temperature dependence of plasmon excitations and their energy dispersion dependence on the direction of the wave vector in the Brillouin zone for graphene [10][11][12][13][14][15], the Klein paradox [16][17][18][19], the Veselago lens [19][20][21], screened impurity potential [22,23], effect of magnetic field [22] to name just a few.…”