arXiv subjects

Tomohiko Saitoh

Publications and source records attributed to Tomohiko Saitoh.

3 recordsLinked to original sources

arXiv2026

CE-antiferromagnetic electronic structure in LaSr$_2$Mn$_2$O$_7$ revealed by micro-focused angle-resolved photoemission spectroscopy and tight-binding models

We have investigated the electronic structure of LaSr$_2$Mn$_2$O$_7$ in the CE-type antiferromagnetic (CE-AFM) state below the Néel temperature using micro-focused angle-resolved photoemission spectroscopy ($μ$-ARPES) and tight-binding models. In agreement with the tight-binding calculations, we found a dispersive intensity around the X point in the $μ$-ARPES spectra, where the A-type antiferromagnetic (A-AFM) phase has no bands experimentally and theoretically, demonstrating that we have successfully captured the signatures of the CE-AFM band structure for the first time. Many observed features can be explained by the CE-AFM tight-binding bands, although some of them and the overall near-Fermi level intensity mapping can be explained by the A-AFM band structure. This indicates that the CE-AFM domain size would be no larger than the beam footprint size of a $\sim\!20$~{\textmu}m scale.

cond-mat.str-el↗

arXiv2020

Photo-excitation band-structure engineering of 2H-NbSe$_2$ probed by time- and angle-resolved photoemission spectroscopy

We investigated the nonequilibrium electronic structure of 2H-NbSe$_2$ by time- and angle-resolved photoemission spectroscopy. We find that the band structure is distinctively modulated by strong photo-excitation, as indicated by the unusual increase in the photoelectron intensities around E$_F$. In order to gain insight into the observed photo-induced electronic state, we performed DFT calculations with modulated lattice structures, and found that the variation of the Se height from the Nb layer results in a significant change in the effective mass and band gap energy. We further study the momentum-dependent carrier dynamics. The results suggest that the relaxation is faster at the K-centered Fermi surface than at the $Γ$-centered Fermi surface, which can be attributed to the stronger electron-lattice coupling at the K-centered Fermi surface. Our demonstration of band structure engineering suggests a new role for light as a tool for controlling the functionalities of solid-state materials.

cond-mat.str-el↗

arXiv2015

Laboratory hard X-ray photoelectron spectroscopy of La$_{1-x}$Sr$_{x}$MnO$_{3}$

A laboratory hard X-ray photoelectron spectroscopy (HXPS) system equipped with a monochromatic Cr K$α$ ($hν= 5414.7$ eV) X-ray source was applied to an investigation of the core-level electronic structure of La$_{1-x}$Sr$_x$MnO$_3$. No appreciable high binding-energy shoulder in the O $1s$ HXPS spectra were observed while an enhanced low binding-energy shoulder structure in the Mn $2p_{3/2}$ HXPS spectra were observed, both of which are manifestation of high bulk sensitivity. Such high bulk sensitivity enabled us to track the Mn $2p_{3/2}$ shoulder structure in the full range of $x$, giving us a new insight into the binding-energy shift of the Mn $2p_{3/2}$ core level. Comparisons with the results using the conventional laboratory XPS ($hν= 1486.6$ eV) as well as those using a synchrotron radiation source ($hν= 7939.9$ eV) demonstrate that HXPS is a powerful and convenient tool to analyze the bulk electronic structure of a host of different compounds.

cond-mat.str-el↗