title: Pseudogap of metallic layered nickelate R(2-x)Sr(x)NiO4 (R = Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy.
abstract: We have investigated charge dynamics and electronic structures for single crystals of metallic layered nickelates, R(2-x)Sr(x)NiO4 (R = Nd, Eu), isostructural to La(2-x)Sr(x)CuO4. Angle-resolved photoemission spectroscopy on the barely metallic Eu(0.9)Sr(1.1)NiO4 (R = Eu, x = 1.1) has revealed a large hole surface of x2-y2 character with a high-energy pseudogap of the same symmetry and comparable magnitude with those of underdoped (x<0.1) cuprates, although the antiferromagnetic interactions are 1 order of magnitude smaller. This finding strongly indicates that the momentum-dependent pseudogap feature in the layered nickelate arises from the real-space charge correlation.
authors.affiliation: Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Uchida
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authors.lastname: Ishizaka
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authors.initials: P
authors.lastname: Hansmann
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authors.lastname: Kaneko
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authors.initials: Y
authors.lastname: Ishida
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authors.lastname: Yang
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authors.lastname: Kumai
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authors.lastname: Toschi
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authors.lastname: Onose
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authors.initials: R
authors.lastname: Arita
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authors.lastname: Held
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authors.initials: OK
authors.lastname: Andersen
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authors.initials: S
authors.lastname: Shin
authors.forename: Y
authors.initials: Y
authors.lastname: Tokura