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論文

Unveiling spin-dependent unoccupied electronic states of Co$$_{2}$$MnGe (Ga) film via Ge (Ga) $$L_{2,3}$$ absorption spectroscopy

吉川 智己*; Antonov, V. N.*; 河野 嵩*; 鹿子木 将明*; 角田 一樹; 宮本 幸治*; 竹田 幸治; 斎藤 祐児; 後藤 一希*; 桜庭 裕弥*; et al.

Physical Review B, 102(6), p.064428_1 - 064428_7, 2020/08

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)

X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopy were applied at the Ge (Ga) $$L_{2,3}$$ edge to unravel the spin-resolved unoccupied electronic states of Co$$_{2}$$MnGe (Ga). Complicated spectral features were observed in both XAS and XMCD spectra. For their interpretation, we compared the experimental XAS and XMCD spectra with the calculated Ge (Ga) 4$$s$$ and 4$$d$$ orbital partial density of states. The comparison enabled a qualitative explanation of the XMCD spectra as the difference between the majority and minority-spin unoccupied density of states summed over the 4$$s$$ and 4$$d$$ orbitals. Our finding provides a new approach to uncover the spin-split partial density of states above the Fermi level.

論文

Element-specific density of states of Co$$_{2}$$MnGe revealed by resonant photoelectron spectroscopy

河野 嵩*; 鹿子木 将明*; 吉川 智己*; Wang, X.*; 角田 一樹*; 宮本 幸治*; 室 隆桂之*; 竹田 幸治; 斎藤 祐児; 後藤 一希*; et al.

Physical Review B, 100(16), p.165120_1 - 165120_6, 2019/10

 被引用回数:1 パーセンタイル:76.22(Materials Science, Multidisciplinary)

Resonant photoelectron spectroscopy at the Co and Mn 2${it p}$ core absorption edges of half-metallic Co$$_{2}$$MnGe has been performed to determine the element-specific density of states (DOS). A significant contribution of the Mn 3${it d}$ partial DOS near the Fermi level ($$E_{F}$$) was clarified by measurement at the Mn 2${it p}$ absorption edge. Further analysis by first-principles calculation revealed that it has $$t_{2g}$$ symmetry, which must be responsible for the electrical conductivity along the line perpendicular to the film plane. The dominant normal Auger contribution observed at the Co 2${it p}$ absorption edge indicates delocalization of photoexcited Co 3${it d}$ electrons. The difference in the degrees of localization of the Mn 3${it d}$ and Co 3${it d}$ electrons in Co$$_{2}$$MnGe is explained by the first-principles calculation.

論文

Magnetic-impurity-induced modifications to ultrafast carrier dynamics in the ferromagnetic topological insulators Sb$$_{2-x}$$V$$_{x}$$Te$$_{3}$$

角田 一樹*; 鹿子木 将明*; Reimann, J.*; Nurmamat, M.*; 後藤 伸一*; 竹田 幸治; 斎藤 祐児; Kokh, K. A.*; Tereshchenko, O. E.*; G$"u$dde, J.*; et al.

New Journal of Physics (Internet), 21(9), p.093006_1 - 093006_8, 2019/09

 被引用回数:1 パーセンタイル:65.14(Physics, Multidisciplinary)

We systematically investigate the magnetic, structural and electronic properties and the ultrafast carrier dynamics in a series of V-doped Sb$$_{2}$$Te$$_{3}$$ samples of composition Sb$$_{2-x}$$V$$_{x}$$Te$$_{3}$$ with x = 0, 0.015 and 0.03. Element specific X-ray magnetic circular dichroism signifies that the ferromagnetism of V-doped Sb$$_{2}$$Te$$_{3}$$ is governed by the p-d hybridization between the host carrier and the magnetic dopant. Time- and angle-resolved photoemission spectroscopy has revealed that the V impurity induced states underlying the topological surface state (TSS) add scattering channels that significantly shorten the duration of transient surface electrons down to 100 fs scale. This is in a sharp contrast to the prolonged duration reported for pristine samples though the TSS is located inside the bulk energy gap of the host in either magnetic or non-magnetic cases. It implies the presence of a mobility gap in the bulk energy gap region of the host material.

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