1990 Fiscal Year Final Research Report Summary
Measurement of the Anisotropic Nature of the Fermi Surface by the Angle Resolved Tunneling Spectroscopy
| Project/Area Number |
62540251
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Waseda University |
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Principal Investigator |
OZAKI Hajime Dept. Elec. Eng. Professor, 理工学部, 教授 (10063679)
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| Co-Investigator(Kenkyū-buntansha) |
ENOMOTO Hiroyuki Dept. Elec. Eng. Research Associate, 理工学部, 助手 (10213563)
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| Project Period (FY) |
1987 – 1989
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| Keywords | Tunneling Spectroscopy / Fermi Surface / Anisotropy / 1T-TaS_2 / CDW Gap |
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| Research Abstract |
This study has proposed a new angle-resolved tunneling spectroscopy, which observes the anisotropic nature of the Fermi surfaces. Using this method, the anisotropy of the charge density wave (CDW) energy gap opened at the Fermi surface of the layered material 1T-TaS_2 has been observed. The tnneling current, which flows across the gap between the cleaved flat surfaces of two crystals, is equivalent to that of many independent parallel STM when the lattice constant a is a > d. When a < d, on the other hand, the tunneling is that between Bloch states in the crystals. In this case, the initial and the final states of the tunneling are specified by the k-vector, whose transverse components are conserved through the tunneling. In the 2-dimensionality material, the Fermi surface is parallelopiped in normal to the layer. The tunneling occurs between materials under low-bias condition, at the cross lines of two parallel parallelopiped Fermi surfaces of the two crystals. When one of the two materials is rotated with respect to the another one within the gap surface, the positions of the cross lines move on the Fermi surface. Thus, the anisotropic nature of the Fermi surface is reflected on the tunneling current. The above mentioned properties are clarified by the computer simulation for the layered material 2H-TaS_2"H. The anisotropy of the CDW gap opened at the Fermi surface of 1T-TaS_2 has been observed by experiment at room temperature.
As a result, it has been shown that the anisotropic nature of the Fermi surface of crystal can be obtained by using a probe material with known Fermi surface which is confined to a narrow region in the Brillouin zone for the one side of the tunnel junction.
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