1996 Fiscal Year Final Research Report Summary
Edge States in Two-Dimensional Electron Gas Systems at High Magnetic Fields Studies in Terms Spectroscopic Approach.
| Project/Area Number |
05402012
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KOMIYAMA Susumu The University of Tokyo, Graduate School of Arts and Sciences, Professor, 大学院・総合文化研究科, 教授 (00153677)
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| Co-Investigator(Kenkyū-buntansha) |
HIRAI Hiroshi The University of Tokyo, Graduate School of Arts and Sciences, Assistant, 大学院・総合文化研究科, 助手 (30251325)
SHIRAKI Yasuhiro The University of Tokyo, Research Center for Advanced Science and Technology, Pr, 先端科学技術研究センター, 教授 (00206286)
KOMIYAMA Daijiro The University of Tokyo, Graduate School of Arts and Sciences, Professor, 大学院・総合文化研究科, 教授 (30114713)
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| Project Period (FY) |
1993 – 1996
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| Keywords | Quantum Hall Effects / Edge states / Cyclotron emission / Edge current / Dispersion relation of edge states / Breakdown of the Quantum Hall effects / Dissipation in quantum Hall devices |
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| Research Abstract |
1. Dispersion relation of edge states : Transport characteristics associated with non-equilibrium edge state distribution indicated that the edge states consist of compressible and incompressible regions at low T below 0.1K but the dispersion smoothes with increasing T up to 0.5K at B=3T.
2. Edge states and bulk states : A consistent calculation taking the excess edge charges into account derived the ratio between the edge current due to chemical potential and the Hall current due to electrostatic potential. Also, the "response current" due to all the electrons responding to the imposed perturbation was distinguished from the "Fermi-surface current" due to the current of the probability amplitude of the electrons on the Fermi surface. These two are alternative definitions of transport current, which lead to the bulk picture and the edge picture of the quantized Hall effedts (QHE), respectively.
Mechanism and location of energy dissipation in the Quantum Hall effects (QHE)
(1) Ultra-high sensitive detectors in the far-infrared (FIR) range were developed to make the aimed studies possible. By using QHE devices, a sensitivity by more than three orders of magnitude higher than that of the conventional Ge photoconductive detectors was achieved.
(2) The cyclotron emission from dissipation-less two-demensional electron gas (2DEG) in the QHE regime was detected by the detectors above. Studies on an array of more than 3000 small Hall bars revealed that there is a threshold Hall voltage for the emission ; eV_H=homega_c/2. The results show that the emission is associated with the injection of electrons from contacts, and contributed to better understanding of the mechanism of exchange of electrons between contacts and the 2DEG system.
4. Nonlocal nature of the breakdown of the QHE : Studies of spatial evolution of longitudinal electric field in Hall bars indicated that the bootstrap-type electron heating causes the QHE to breakdown.
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