Trigonal warping, pseudodiffusive transport, and finite-system version of the Lifshitz transition in magnetoconductance of bilayer graphene Corbino disks

Using the transfer matrix in the angular-momentum space we investigate the impact of trigonal warping on magnetotransport and scaling properties of a ballistic bilayer graphene in the Corbino geometry. Although the conductivity at the charge-neutrality point and zero magnetic field exhibits a one-pa...

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Veröffentlicht in:Physical review. B 2016-02, Vol.93 (7), Article 075419
Hauptverfasser: Rut, Grzegorz, Rycerz, Adam
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Sprache:eng
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Zusammenfassung:Using the transfer matrix in the angular-momentum space we investigate the impact of trigonal warping on magnetotransport and scaling properties of a ballistic bilayer graphene in the Corbino geometry. Although the conductivity at the charge-neutrality point and zero magnetic field exhibits a one-parameter scaling, the shot-noise characteristics, quantified by the Fano factor [scriptF] and the third charge-transfer cumulant [scriptR], remain pseudodiffusive. This shows that the pseudodiffusive transport regime in bilayer graphene is not related to the universal value of the conductivity but can be identified by higher charge-transfer cumulants. For Corbino disks with larger radii ratios, the conductivity is suppressed by the trigonal warping, mainly because the symmetry reduction amplifies backscattering for normal modes corresponding to angular-momentum eigenvalues + or -2h. Weak magnetic fields enhance the conductivity, reaching the maximal value near the crossover field B sub(L)=[4/3] 3(h/e)t't[middot]'[(ProQuest: ... denotes formulae and/or non-USASCII text omitted)(R sub(o)- R sub(i))] super(-1), where t sub(0)() is the nearest-neighbor intralayer (interlayer) hopping integral, t' is the skew-interlayer hopping integral, and R sub(o)(R sub(i)) is the outer (inner) disk radius. For magnetic fields B[> ~]B sub(L) we observe quasiperiodic conductance oscillations characterized by the decreasing mean value [left angle bracket][sigma][right angle bracket]-[sigma] sub(0)B sub(L)/B, where [sigma] sub(0)= (8/[pi])e super(2)/h. The conductivity, as well as higher charge-transfer cumulants, show beating patterns with an envelope period proportional to B/B sub(L). This constitutes a qualitative difference between the high-field (BB sub(L)) magnetotransport in the t'=0 case [earlier discussed in Rut and Rycerz, J. Phys.: Condens. Matter 26, 485301 (2014)] and in the t'[middot]0 case, providing a finite-system analog of the Lifshitz transition.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.93.075419