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arXiv 0904.1996cond-mat.mes-hallcond-mat.str-el
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石墨烯中N=0量子霍尔态的击穿:两种绝缘状态

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

摘要:

我们研究了高迁移率石墨烯样品在高达18 T的磁场下在电荷中性点(CNP)附近出现的不寻常的量子霍尔效应(QHE)。我们观察到故障的离域QHE运输和强烈的增加,随着朗道能级填充$ν< 2$,在那里我们确定两个绝缘制度的折射率$ρ_{xx},|ρ_{xy}|$。对于$1 \gtrsim |ν| \gtrsim 1/2$,我们发现$ρ_{xx,xy} \sim e^{a(H-H_c)}$在高达几个电阻量子$R_K$的范围内呈指数增加,而霍尔效应逐渐消失,与具有局部输运的霍尔绝缘体(HI)一致。然后,在$ν\approx 1/2$处,$ρ_{xx}(H)$中的尖点之后是甚至更快的生长的开始,指示向集体绝缘体(CI)状态的转变。这种状态的可能候选者是钉扎维格纳晶体。

英文摘要:

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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