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On the direct insulator-quantum Hall transition in two-dimensional electron systems in the vicinity of nanoscaled scatterers.

Liang CT, Lin LH, Kuang Yoa C, Lo ST, Wang YT, Lou DS, Kim GH, Yuan-Huei C, Ochiai Y, Aoki N, Chen JC, Lin Y, Chun-Feng H, Lin SD, Ritchie DA - Nanoscale Res Lett (2011)

Bottom Line: Such a transition has been attracting a great deal of both experimental and theoretical interests.In this study, we present three different two-dimensional electron systems (2DESs) which are in the vicinity of nanoscaled scatterers.All these three devices exhibit a direct I-QH transition, and the transport properties under different nanaoscaled scatterers are discussed.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan. ctliang@phys.ntu.edu.tw.

ABSTRACT
A direct insulator-quantum Hall (I-QH) transition corresponds to a crossover/transition from the insulating regime to a high Landau level filling factor ν > 2 QH state. Such a transition has been attracting a great deal of both experimental and theoretical interests. In this study, we present three different two-dimensional electron systems (2DESs) which are in the vicinity of nanoscaled scatterers. All these three devices exhibit a direct I-QH transition, and the transport properties under different nanaoscaled scatterers are discussed.

No MeSH data available.


ρxx(B) at various temperatures ranging from 0.3 to 4 K (Sample C). ρxx at T = 0.3 K and T = 4 K are shown.
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Figure 5: ρxx(B) at various temperatures ranging from 0.3 to 4 K (Sample C). ρxx at T = 0.3 K and T = 4 K are shown.

Mentions: Figure 5 shows magnetoresistance measurements on Sample C as a function of magnetic field at various temperatures. It can be seen that the 2DES undergoes a 0-8 transition characterized by an approximately temperature-independent point in ρ xxat the crossing field Bc. Near the crossing field, ρxxis very close to ρxythough ρxyshows a weak T dependence. For B <Bc, no resistance oscillation is observed. At first glance, our experimental results are consistent with Huckestein's model. However, it is noted that Landau quantization should be linked with quantum mobility, not classical Drude mobility [36]. Moreover, the observed oscillations for B >Bc do not always correspond to formation of quantum Hall states. As mentioned in our previous study [36], the observed oscillations can be well approximated by conventional Shubnikov-de Haas (SdH) formalism. It is noted that the SdH formula is derived without considering quantum localization effects which give rise to formation of quantum Hall state. Therefore, quantum localization effects are not significant in the system under this study. Actually, as shown in Figure 6, the crossing point in σxy at around 7.9 Tmay correspond to the extended states due to the onset of the strong localization effects. Therefore, in this study, the onset of strong localization actually occurs at a magnetic field approximately 4 Thigher than the crossing point.


On the direct insulator-quantum Hall transition in two-dimensional electron systems in the vicinity of nanoscaled scatterers.

Liang CT, Lin LH, Kuang Yoa C, Lo ST, Wang YT, Lou DS, Kim GH, Yuan-Huei C, Ochiai Y, Aoki N, Chen JC, Lin Y, Chun-Feng H, Lin SD, Ritchie DA - Nanoscale Res Lett (2011)

ρxx(B) at various temperatures ranging from 0.3 to 4 K (Sample C). ρxx at T = 0.3 K and T = 4 K are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211178&req=5

Figure 5: ρxx(B) at various temperatures ranging from 0.3 to 4 K (Sample C). ρxx at T = 0.3 K and T = 4 K are shown.
Mentions: Figure 5 shows magnetoresistance measurements on Sample C as a function of magnetic field at various temperatures. It can be seen that the 2DES undergoes a 0-8 transition characterized by an approximately temperature-independent point in ρ xxat the crossing field Bc. Near the crossing field, ρxxis very close to ρxythough ρxyshows a weak T dependence. For B <Bc, no resistance oscillation is observed. At first glance, our experimental results are consistent with Huckestein's model. However, it is noted that Landau quantization should be linked with quantum mobility, not classical Drude mobility [36]. Moreover, the observed oscillations for B >Bc do not always correspond to formation of quantum Hall states. As mentioned in our previous study [36], the observed oscillations can be well approximated by conventional Shubnikov-de Haas (SdH) formalism. It is noted that the SdH formula is derived without considering quantum localization effects which give rise to formation of quantum Hall state. Therefore, quantum localization effects are not significant in the system under this study. Actually, as shown in Figure 6, the crossing point in σxy at around 7.9 Tmay correspond to the extended states due to the onset of the strong localization effects. Therefore, in this study, the onset of strong localization actually occurs at a magnetic field approximately 4 Thigher than the crossing point.

Bottom Line: Such a transition has been attracting a great deal of both experimental and theoretical interests.In this study, we present three different two-dimensional electron systems (2DESs) which are in the vicinity of nanoscaled scatterers.All these three devices exhibit a direct I-QH transition, and the transport properties under different nanaoscaled scatterers are discussed.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan. ctliang@phys.ntu.edu.tw.

ABSTRACT
A direct insulator-quantum Hall (I-QH) transition corresponds to a crossover/transition from the insulating regime to a high Landau level filling factor ν > 2 QH state. Such a transition has been attracting a great deal of both experimental and theoretical interests. In this study, we present three different two-dimensional electron systems (2DESs) which are in the vicinity of nanoscaled scatterers. All these three devices exhibit a direct I-QH transition, and the transport properties under different nanaoscaled scatterers are discussed.

No MeSH data available.