System-Size Dependence of Quantum Hall Transitions

Nakajima, Takashi; Ueda, Taisei; Komiyama, S.

doi:10.1143/jpsj.76.094703

Cited by 22 publications

(61 citation statements)

References 38 publications

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“…Below T coh , R H decreases rapidly as the temperature is lowered. Further decrease of temperature increases R H after showing a minimum at around 5 K. The magnitude of R H above T coh matches well with that of bulk single crystal [15]. The enhancement of the absolute value of R H below T coh is nearly 15 times that at above T coh , which is nearly half of that in bulk single crystal.…”

supporting

confidence: 74%

“…The first is the reduction of AF fluctuations and the second is the increase of isotropic impurity scattering by nonmagnetic Yb-ions. In the former case, since the system is tuned away from the quantum critical point, the Tlinear resistivity is expected to change to T 2 -dependence accompanied by a reduction of ρ 0 [15]. However, such a trend is not observed here.…”

mentioning

confidence: 68%

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Strong suppression of superconductivity by divalent ytterbium Kondo holes in CeCoIn5

et al. 2012

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To study the nature of partially substituted Yb-ions in a Ce-based Kondo lattice, we fabricated high quality Ce1−xYbxCoIn5 epitaxial thin films using molecular beam epitaxy. We find that the Yb-substitution leads to a linear decrease of the unit cell volume, indicating that Yb-ions are divalent forming Kondo-holes in Ce1−xYbxCoIn5, and leads to a strong suppression of the superconductivity and Kondo coherence. These results, combined with the measurements of Hall effect, indicate that Yb-ions act as nonmagnetic impurity scatters in the coherent Kondo lattice without serious suppression of the antiferromagnetic fluctuations. These are in stark contrast to previous studies performed using bulk single crystals, which claim the importance of valence fluctuations of Yb-ions. The present work also highlights the suitability of epitaxial films in the study of the impurity effect on the Kondo lattice.

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confidence: 74%

mentioning

confidence: 68%

Strong suppression of superconductivity by divalent ytterbium Kondo holes in CeCoIn5

et al. 2012

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“…Below T ≈ 50 K, R H becomes field dependent and its magnitude is significantly enhanced. Very similar behavior of R H (T, B) in CeCoIn 5 and CeRhIn 5 was attributed to antiferromagnetic spin fluctuations causing highly anisotropic scattering time [20]. For the highest applied magnetic field (B = 12.5 T), R H changes sign for positive for 30 T 50 K. This can be a result of skew-scattering or/and multiband compensation.…”

mentioning

confidence: 73%

Quantum criticality in Ce2PdIn8: A thermoelectric study

2011

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We report the Nernst effect (ν) and thermoelectric power (S) data for the Ce2PdIn8 heavyfermion compound. Both S and ν behave anomalously at low temperatures: the thermopower shows a Kondo-like maximum at T = 37 K, while the Nernst coefficient becomes greatly enhanced and field dependent below T ≈ 30 K. In the zero-T limit S/T and ν/T diverge logarithmically, what is related to occurrence of the quantum critical point (QCP). Presented results suggest that the antiferromagnetic spin-density-wave scenario may be applicable to QCP in Ce2PdIn8. PACS numbers: 72.15.Jf, 74.40.Kb, 74.70.Tx The physical properties of matter in the vicinity of quantum critical point (QCP) has been intensively studied for the last two decades. A relation between QCP and unconventional superconductivity, as well as other unusual properties of the electronic system near QCP have attracted much attention, although this complex topic is far from being well understood. Measurements of the thermoelectric effects, which are particularly sensitive to distribution of the density of the electronic states and variation of the relaxation time around the Fermi surface, turn out to be an effective method to detect departures from the Landau description of metals [1][2][3][4][5]. However, an interpretation of these anomalies is not straightforward, since there exist a wide variety of overlapping to some extent models that attempt to explain the unusual thermoelectric behavior. For instance, one can mention here the models of d-wave-(dDW) , spin-(SDW), charge-(CDW), and unconventional-(UDW) density-waves [6,7], magnetic-field-induced chiral order [8], superconducting vortices (or vortex-like excitations) [9], superconducting fluctuations [10], current vertex correction [11]. Even though, studies on temperature and/or magnetic field variations of the Nernst coefficient and the thermoelectric power have been recognized as very helpful tools in distinguishing between possible types of quantum criticality [12][13][14].In this Letter we investigate the transport properties of the Ce 2 PdIn 8 heavy-fermion (HF) compound that exhibits unconventional superconductivity below T c = 0.7 K [15]. We focus on the thermoelectric phenomena which appear to be highly anomalous in the low temperature region. Both the Nernst effect and the thermoelectric power show below T ≈ 7 K features that can be attributed to presence of the quantum critical point.High-quality polycrystalline sample of Ce 2 PdIn 8 was prepared and characterized as described in Ref. [16]. The resistivity was measured using the four-probe technique with 25 µm gold wires attached to the bar-shaped sample with two component silver epoxy (EPO-TEK H20E). For the Hall coefficient measurement, the sample was mounted on a rotatable probe and continuously turned by 180 degree (face down and up) in a magnetic field (B) of 12.5 T to effectively reverse the field anti-symmetrical signal. During the thermoelectric power and Nernst coefficient measurements, the sample was clamped between two phosphor bronze blocks,...

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“…21-23 Moreover, in all the theoretical studies on the I-QH transition, the carrier density is assumed to be constant, independent of both temperature and magnetic field. 27-29 Therefore the reservoir model describing charge transfer between epitaxial graphene and the SiC substrate as a function of B (Ref. 16) should not play an important role in the observed low-field I-QH transition in the work of Pallecchi et al.…”

Section: Resultsmentioning

confidence: 99%

“…16 Moreover, in EG grown on SiC, 17, 18 E F can be pinned to the localized states 19 such that the ν = 2 QH plateau extends from a low field (∼ 1 T) to exceptionally high values (30 T), 20 making EG an ideal system for studying an isolated low-field QH transition, although no such high-field transition has been reported. A possible reason for this is the reservoir model responsible for the long ν = 2 QH plateau 19 so that one does not observe the high-field insulating state.…”

Section: Methodsmentioning

confidence: 99%

Insulator-quantum Hall transition in monolayer epitaxial graphene

et al. 2016

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We report on magneto-transport measurements on low-density, large-area monolayer epitaxial graphene devices grown on SiC. We observe temperature (T)-independent crossing points in the longitudinal resistivity ρxx, which are signatures of the insulator-quantum Hall (I-QH) transition, in all three devices. Upon converting the raw data into longitudinal and Hall conductivities σxx and σxy, in the most disordered device, we observed T-driven flow diagram approximated by the semi-circle law as well as the T-independent point in σxy near e2/h. We discuss our experimental results in the context of the evolution of the zero-energy Landau level at low magnetic fields B. We also compare the observed strongly insulating behaviour with metallic behaviour and the absence of the I-QH transition in graphene on SiO2 prepared by mechanical exfoliation.

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System-Size Dependence of Quantum Hall Transitions

Cited by 22 publications

References 38 publications

Strong suppression of superconductivity by divalent ytterbium Kondo holes in CeCoIn5

Strong suppression of superconductivity by divalent ytterbium Kondo holes in CeCoIn5

Quantum criticality in Ce2PdIn8: A thermoelectric study

Insulator-quantum Hall transition in monolayer epitaxial graphene

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