Coexistence of electron and hole transport in graphene

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. When sweeping the carrier concentration in monolayer graphene through the charge neutrality point, the experimentally measured Hall resistivity shows a smooth zero crossing. Using a two-component model of coexisting electrons and holes around the charge neutrality point, we unambiguously show that both types of carriers are simultaneously present. For high magnetic fields up to 30 T the electron and hole concentrations at the charge neutrality point increase with the degeneracy of the zero-energy Landau level, which implies a quantum Hall metal state at ν = 0 made up by both electrons and holes.

Physics of a disordered Dirac point in epitaxial graphene from temperature-dependent magnetotransport measurements

“…Similar two-carrier analyses are also found in the literature for this electron-hole coexistence regime in monolayer and bilayer graphene [19,20]. The carrier density directly extracted from this two-carrier low-field Hall effect is, therefore, effectively,…”

Magnetic field driven ambipolar quantum Hall effect in epitaxial graphene close to the charge neutrality point

“…For graphene on SiO 2 , close to the CNP, QHE reveals that electrons and holes coexist even when the energy spectrum is quantized and the carriers partially localized [15,16], but for G/SiC even this rather intuitive picture has not been thoroughly tested. The amplitude of the disorder potential fluctuation has been evaluated by various methods [5,17], but the type of disorder and its spatial and energy distribution close to the CNP remain mostly unknown.…”

Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

“…3 In the spin-first scenario, there exists a pair of counterpropagating chiral edge states (with opposite spins) in the gap so that a quantized Hall state at ν = 0 appears. [4][5][6] These states provide a dominant contribution to the conductivity, while the bulk transport is suppressed by the energy gap. This leads to divergence of the longitudinal resistivity ρ xx and smooth zero crossing of the Hall resistivity ρ yx .…”

“…In the valley-first scenario, no edge states exist in the gap and the divergence of both ρ xx and ρ yx at ν = 0 is expected. [3][4][5] Since an unconventional quantum Hall state at ν = 0 does not rely on relativistic dispersion of excitation, which is a specific case of graphene, it can be realized in other materials where two-dimensional (2D) electrons and holes coexist. The wide CdHgTe/HgTe/CdHgTe quantum wells, where separation of the size-quantized subbands is relatively small, are of particular interest in this connection.…”