Insulator-quantum Hall conductor transitions at low magnetic field

Huang, Chi‐Feng; Chang, Y. H.; Lee, C. H.; Chou, Hong‐Nong; Yeh, H. D.; Liang, Chi‐Te; Chen, Y. F.; Lin, H. H.; Cheng, Hao-Tien; Hwang, Gan-Lin

doi:10.1103/physrevb.65.045303

Cited by 30 publications

(20 citation statements)

References 18 publications

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“…The crossing point and some other physical quantities are listed in Table 1. We note that for the same numbers of layer, the crossing field B c is lower when the mobility μ is higher, consistent with the results obtained in conventional GaAs-based 2D systems [39,40]. Moreover, the spin degree of freedom does not play an important role in the observed direct I-QH transition [41-45].…”

Section: Resultssupporting

confidence: 88%

Dirac fermion heating, current scaling, and direct insulator-quantum Hall transition in multilayer epitaxial graphene

et al. 2013

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We have performed magnetotransport measurements on multilayer epitaxial graphene. By increasing the driving current I through our graphene devices while keeping the bath temperature fixed, we are able to study Dirac fermion heating and current scaling in such devices. Using zero-field resistivity as a self thermometer, we are able to determine the effective Dirac fermion temperature (TDF) at various driving currents. At zero field, it is found that TDF ∝ I≈1/2. Such results are consistent with electron heating in conventional two-dimensional systems in the plateau-plateau transition regime. With increasing magnetic field B, we observe an I-independent point in the measured longitudinal resistivity ρxx which is equivalent to the direct insulator-quantum Hall (I-QH) transition characterized by a temperature-independent point in ρxx. Together with recent experimental evidence for direct I-QH transition, our new data suggest that such a transition is a universal effect in graphene, albeit further studies are required to obtain a thorough understanding of such an effect.

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Section: Resultssupporting

confidence: 88%

Dirac fermion heating, current scaling, and direct insulator-quantum Hall transition in multilayer epitaxial graphene

et al. 2013

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“…Since the minima in B of the SdH oscillations do not shift at different temperatures as shown in the inset of Figure 3, the carrier density is T -independent and is calculated to have the value n SdH = 1.140 × 10 12 cm −2 from n = νBe/h , as shown in Figure 4. The peak positions at around B = 6 T in Figure 3 are shown to move with increasing temperature as a feature of scaling behavior of standard quantum Hall theory [27]. …”

Section: Resultsmentioning

confidence: 99%

Temperature dependence of electron density and electron–electron interactions in monolayer epitaxial graphene grown on SiC

et al. 2017

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We report carrier density measurements and electron-electron (e-e) interactions in monolayer epitaxial graphene grown on SiC. The temperature (T)-independent carrier density determined from the Shubnikov-de Haas (SdH) oscillations clearly demonstrates that the observed logarithmic temperature dependence of Hall slope in our system must be due to e-e interactions. Since the electron density determined from conventional SdH measurements does not depend on e-e interactions based on Kohn's theorem, SdH experiments appear to be more reliable compared with the classical Hall effect when one studies the T dependence of the carrier density in the low T regime. On the other hand, the logarithmic T dependence of the Hall slope δRxy/δB can be used to probe e-e interactions even when the conventional conductivity method is not applicable due to strong electron-phonon scattering.

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“…The essential physics can be illustrated qualitatively in a percolation picture, as sketched in Fig. 1(a), which is closely analogous to the physics underlying the QH plateau-to-plateau transitions in disordered 2DEGs [16][17][18]. For a smoothly varying potential, three regions can be identified: the QAH phase when the chemical potential lies in the Zeeman exchange gap induced by ferromagnetism; the metallic phase when the chemical potential lies in the valence band; and an intermediate mixed region where QAH and metallic domains coexist.…”

mentioning

confidence: 91%

Observation of the Quantum Anomalous Hall Insulator to Anderson Insulator Quantum Phase Transition and its Scaling Behavior

Chang

Zhao

et al. 2016

Phys. Rev. Lett.

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Fundamental insight into the nature of the quantum phase transition from a superconductor to an insulator in two dimensions, or from one plateau to the next or to an insulator in the quantum Hall effect, has been revealed through the study of its scaling behavior. Here, we report on the experimental observation of a quantum phase transition from a quantum-anomalous-Hall insulator to an Anderson insulator in a magnetic topological insulator by tuning the chemical potential. Our experiment demonstrates the existence of scaling behavior from which we extract the critical exponent for this quantum phase transition. We expect that our work will motivate much further investigation of many properties of quantum phase transition in this new context. DOI: 10.1103/PhysRevLett.117.126802 The quantum anomalous Hall (QAH) state is a topological quantum state displaying quantized Hall resistance and zero longitudinal resistance, similar to the quantum Hall (QH) state. However, while the QH effect requires a large external magnetic field, the origin of the QAH effect is the exchange interaction between electron spin and magnetic moments in ferromagnetic materials, and thus can occur even in the absence of an external magnetic field [1][2][3]. Ever since the discovery of the QAH effect in magnetically doped ðBi; SbÞ 2 Te 3 films [2][3][4][5][6][7], intensive research effort has focused on the global phase diagram and the novel transport properties of this effect, including nonlocal transport [6,8], zero Hall conductance plateau [9][10][11], delocalization behavior [7], and giant anisotropic magnetoresistance [12]. These experimental observations reveal an equivalence between the QAH effect and QH effect in terms of their topological nature.In the QH effect, the appearance of stable quantized Hall plateaus is intimately tied to the Anderson localization of bulk carriers of a two dimensional electron gas (2DEG) under a strong external magnetic field. The quantum phase transition (QPT) point between two Hall plateaus (known as plateau to plateau transition) is marked by the emergence of an extended state, which can be viewed, for a smoothly varying disorder, as the transition where the QH droplets of a state with one Chern number in the background of a QH state of another Chern number begin to percolate. Since this percolation process involves quantum tunneling between nearby chiral edge modes encircling individual droplets, it leads to a different critical exponent from that describing a classical percolation transition [13][14][15]. The QPT between an insulator and ν ¼ 1 plateau belongs to the same universality class as the plateau to plateau transition, and serves as the prototype for the QPT studied in the present work. In the QAH effect, one may expect a similar percolation picture for chiral edge states around magnetic domains at the quantum critical point. In the experiment by Checkelsky et al. [7], evidence for quantum criticality and delocalization was shown while approaching the QAH state, but the scaling behavior was...

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Insulator-quantum Hall conductor transitions at low magnetic field

Cited by 30 publications

References 18 publications

Dirac fermion heating, current scaling, and direct insulator-quantum Hall transition in multilayer epitaxial graphene

Dirac fermion heating, current scaling, and direct insulator-quantum Hall transition in multilayer epitaxial graphene

Temperature dependence of electron density and electron–electron interactions in monolayer epitaxial graphene grown on SiC

Observation of the Quantum Anomalous Hall Insulator to Anderson Insulator Quantum Phase Transition and its Scaling Behavior

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