Magnetoconductance of the Corbino disk in graphene: Chiral tunneling and quantum interference in the bilayer case

Abstract

Quantum transport through an impurity-free Corbino disk in bilayer graphene is investigated analytically, by the mode-matching method for effective Dirac equation, in the presence of uniform magnetic fields. Similarly as in the monolayer case (see Refs. [1,2]), conductance at the Dirac point shows oscillations with the flux piercing the disk area $\hat{I}{¦}_D$ characterized by the period $\hat{I}{¦}_0=2(h/e)\ln (R_{\mathrm{o}}/R_{\mathrm{i}})$, where $R_{\mathrm{o}}$ ($R_{\mathrm{i}}$) is the outer (inner) disk radius. The oscillations magnitude depends either on the radii ratio or on the physical disk size, with the condition for maximal oscillations reading $R_{\mathrm{o}}/R_{\mathrm{i}}\simeq {\left[R_{\mathrm{i}}{t}_{\perp }/(2\hslash v_F)\right]}^{4/p}$ (for $R_{\mathrm{o}}/R_{\mathrm{i}}\gg 1$), where $t_{\perp }$ is the interlayer hopping integral, $v_F$ is the Fermi velocity in graphene, and $p$ is an {\em even} integer. {\em Odd}-integer values of $p$ correspond to vanishing oscillations for the normal Corbino setup, or to oscillations frequency doubling for the Andreev-Corbino setup. At higher Landau levels (LLs) magnetoconductance behaves almost identically in the monolayer and bilayer cases. A brief comparison with the Corbino disk in 2DEG is also provided in order to illustrate the role of chiral tunneling in graphene.

Typos corrected; acknowledgment added. RevTeX, 13 pages, 7 figures