Nonlinear transport of graphene in the quantum Hall regime

Abstract

We have studied the breakdown of the integer quantum Hall (QH) effect with fully broken symmetry, in an ultra-high mobility graphene device sandwiched between two single crystal hexagonal boron nitride substrates. The evolution and stabilities of the QH states are studied quantitatively through the nonlinear transport with dc Hall voltage bias. The mechanism of the QH breakdown in graphene and the movement of the Fermi energy with the electrical Hall field are discussed. This is the first study in which the stabilities of fully symmetry broken QH states are probed all together. Our results raise the possibility that the = ±6 states might be a better target for the quantum resistance standard. IntroductionGraphene, a single layer of graphite, has continued to attract great attention from the scientific and technical communities due to the rich physics of Dirac fermions and the great potential for technological applications [1]. Started from the half-integer and the four fold degeneracy without symmetry breaking of spin or valley degrees of freedom, the quantum Hall (QH) resistance in graphene is expected to be the series of filling factor = ±2, ±6, ±10……., and those Hall plateaus have been experimentally observed since 2005 [2,3]. With the technique of suspending graphene [4] and transferring graphene onto single crystal hexagonal boron nitride (hBN) [5], one can suppress the scattering of carriers from charged impurities [6] and substrate phonons [7], resulting in substantially improved carrier mobility. Symmetry-broken integer QH states and fractional QH states were soon discovered on the improved devices [8][9][10][11][12][13][14][15].Although most of the integer QH and fractional QH studies have been carried in GaAs/AlGaAs heterostructure for its extremely high mobility, similar studies in graphene have attracted lots of attention for a variety of reasons including the peculiar band structure of graphene and the exposure of the two dimensional electron gas (2DEG) in graphene. One interesting question has been raised that if graphene can replace GaAs to be the base of the resistance standard [16,17]. The QH effect has been applied on the resistance unit in the 2 international system since 1990 [18]. However, a redefinition of SI basic units (Kilogram, Ampere, Kelvin and Mole) by 2018 [19] involves the resistance standard from the QH effect. Therefore, the metrology of resistance standard, including a practical (non-SI) definition for increasing potential end users, is getting more and more important. Various works have proved the universality and reproducibility of quantum Hall resistance standard metrology in graphene with accuracy as high as part-per-billion [20][21][22][23][24]. Quantum resistance devices based on graphene have been realized on graphene grown on silicon carbide wafer [20][21][22][23][24][25][26]. More importantly, QH effect can be realized in graphene at room temperature [27], which makes graphene-based QH device a very attractive choice of a practical resistance definition for routine...

Plasmon damping rates in Coulomb-coupled two-dimensional layers in a heterostructure

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Phonon-mediated magneto-resonances in biased graphene layers

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“…These studies were primarily done in the near-equilibrium limit with a small electric field applied laterally. The fate of quantum Hall effect and magneto oscillations in graphene when subjected to strong electric fields and high currents has received much less attention [19][20][21][22]. Importantly, such non-equilibrium effects are relevant in the context of electron interferometers using edge channels for quantum information processing [23,24], generation of excitations such as magnetoplasmons in the edge channels [25] and for the application of the quantum Hall effect as a resistance standard [22,26].…”