Browsing by Author "Chin, Y. Y."

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Electronic structure investigation of a charge density wave coupled to a metal-to-metal transition in Ce3Co4Sn13
(2018-12-18)
Singh, A.
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Huang, H. Y.
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Chin, Y. Y.
;
Liao, Y. F.
;
Huang, T. C.
We study the electronic structure of the skutterudite Ce3Co4Sn13, which is known to exhibit a charge density wave (CDW) transition, at temperature T-CDW similar to 160 K, coupled to a metal-to-metal transition. We use temperature dependent hard x-ray photoemission spectroscopy (HAXPES) and x-ray absorption spectroscopy (XAS) to investigate the occupied and unoccupied electronic states of Ce3Co4Sn13. The Co 2p and Sn 3p core level spectra show small but finite shifts in binding energy positions across T-CDW while Ce 3d core level spectra do not show any change across the transition. The Ce M-4,M-5-edge XAS spectrum compared with calculations indicate a typical trivalent ionic Ce3+ spectral shape, ruling out Kondo screening in Ce3Co4Sn13. In contrast, the Co L-2,L-3-edge XAS spectrum compared with a calculated spectrum shows evidence for hybridization with neighboring Sn atoms in a trigonal prismatic co-ordination. Temperature dependent XAS across the Co L-2,L-3-edge shows a small shift across T-CDW, consistent with HAXPES results. Detailed XAS measurements as a function of temperature show that the spectral shifts occur with a hysteresis across T-CDW , indicative of a first-order transition. Valence band spectra show a normal Fermi edge above and below T-CDW. The Co 3d states are observed at a binding energy of similar to 2 eV while the Ce 4f states occur as a weak feature within 0.5 eV of the Fermi level. The results suggest an unusual CDW transition coupled to a metal-to-metal transition in Ce3Co4Sn13.
Strong orbital polarization in orthorhombic DyMnO(3): A combined x-ray linear dichroism and ab initio electronic structure study
(2010-05-15)
Chen, J. M.
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Hu, Z.
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Jeng, H. T.
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Chin, Y. Y.
;
Lee, J. M.
We present a combined experimental and theoretical study on the Mn 3d orbital occupation in orthorhombic DyMnO(3) single crystals. We have observed a very strong polarization dependence in the Mn L(2,3) x-ray absorption spectra, indicative for a distinct anisotropic orbital occupation. Ab initio electronic-structure calculations clearly infer the existence of a strong orbital polarization in the e(g) band with a staggered d(3x2-r2)/d(3y2-r2)-type ordering pattern in the ab plane. This finding is in excellent agreement with a quantitative analyis of the spectra using the atomic multiplet cluster approach.
Strong orbital polarization in orthorhombic DyMnO3: A combined x-ray linear dichroism and ab initio electronic structure study
(2010-05-15)
Chen, J. M.
;
Hu, Z.
;
Jeng, H. T.
;
Chin, Y. Y.
;
Lee, J. M.
We present a combined experimental and theoretical study on the Mn 3d orbital occupation in orthorhombic DyMnO3 single crystals. We have observed a very strong polarization dependence in the Mn L-2,L-3 x-ray absorption spectra, indicative for a distinct anisotropic orbital occupation. Ab initio electronic-structure calculations clearly infer the existence of a strong orbital polarization in the e(g) band with a staggered d(3x2-r2)/d(3y2-r2)-type ordering pattern in the ab plane. This finding is in excellent agreement with a quantitative analyis of the spectra using the atomic multiplet cluster approach.
The unconventional doping in YBa2Cu3O7-x/La0.7Ca0.3MnO3 heterostructures by termination control
(2017-01-16)
Tra, V. T.
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Huang, R.
;
Gao, X.
;
Chen, Y. -J.
;
Liu, Y. T.
In strongly correlated oxides, heterostructures provide a powerful route to manipulate the charge, spin, orbital, and lattice degrees of freedom to create distinctive functionalities. In this work, we have achieved atomically precise interface control in YBa2Cu3O7-x/La0.7Ca0.3MnO3 (YBCO/LCMO) heterostructures and find a hidden effective doping. This mechanism is responsible for higher Tc in the sample with the MnO2-terminated interface than in that with the La0.7Ca0.3O-terminated interface. The MnO2-terminated sample also shows a larger magnetic moment of Mn together with a lower valence state. For more than a decade, the control of T-c in these heterostructures prior to this work has been solely via the variation of YBCO or LCMO thickness. This work hints at an alternative way of exploiting and exploring the interactions between superconductivity and magnetism in this system. Published by AIP Publishing.