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arXiv · 0904.1996

Breakdown of the N=0 Quantum Hall State in graphene: two insulating regimes

L. Zhang·J. Camacho·H. Cao·Y. P. Chen·M. Khodas·D. Kharzeev·A. Tsvelik·T. Valla·I. A. Zaliznyak
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Abstract

We studied the unusual Quantum Hall Effect (QHE) near the charge neutrality point (CNP) in high-mobility graphene sample for magnetic fields up to 18 T. We observe breakdown of the delocalized QHE transport and strong increase in resistivities $ρ_{xx},|ρ_{xy}|$ with decreasing Landau level filling for $ν< 2$, where we identify two insulating regimes. For $1 \gtrsim |ν| \gtrsim 1/2$ we find an exponential increase of $ρ_{xx,xy} \sim e^{a(H-H_c)}$ within the range up to several resistance quanta $R_K$, while the Hall effect gradually disappears, consistent with the Hall insulator (HI) with local transport. Then, at $ν\approx 1/2$ a cusp in $ρ_{xx}(H)$ followed by an onset of even faster growth indicates transition to a collective insulator (CI) state. The likely candidate for this state is a pinned Wigner crystal.

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L. Zhang, J. Camacho, H. Cao, Y. P. Chen, M. Khodas, D. Kharzeev, A. Tsvelik, T. Valla, I. A. Zaliznyak. 2009-09-04. Breakdown of the N=0 Quantum Hall State in graphene: two insulating regimes. https://doi.org/10.1103/physrevb.80.241412

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