We have studied the electronic structure of ferrimagnetic Mn2VAl single crystals by means of soft X-ray absorption spectroscopy (XAS), X-ray absorption magnetic circular dichroism (XMCD) and resonant soft X-ray inelastic scattering (RIXS). We have successfully observed the XMCD signals for all the constitute elements. The Mn L2,3 XAS and XMCD spectra are reproduced by spectral simulations based on density-functional theory, indicating the itinerant character of the Mn 3d states. On the other hand, the V 3d electrons are rather localized since the ionic model can qualitatively explain the V L2,3 XAS and XMCD spectra. This picture is consistent with local dd excitations revealed by the V L3 RIXS.

In this study, we systematically investigate three-dimensional (3D) momentum ( k)-resolved electronic structures of Ruddlesden-Popper-type iridium oxides Sr n+1 Ir n O 3n+1 using soft-x-ray (SX) angle-resolved photoemission spectroscopy (ARPES). Our results provide direct evidence of an insulator-to-metal transition that occurs upon increasing the dimensionality of the IrO 2 -plane structure. This transition occurs when the spin-orbit-coupled j eff = 1/2 band changes its behavior in the dispersion relation and moves across the Fermi energy. In addition, an emerging band along the (0,0,0)-R(π,π,π) direction is found to play a crucial role in the metallic characteristics of SrIrO 3 . By scanning the photon energy over 350 eV, we reveal the 3D Fermi surface in SrIrO 3 and k z -dependent oscillations of photoelectron intensity in Sr 3 Ir 2 O 7 . In contrast to previously reported results obtained using low-energy photons, folded bands derived from lattice distortions and/or magnetic ordering make significantly weak (but finite) contributions to the k-resolved photoemission spectrum. At the first glance, this leads to the ambiguous result that the observed k-space topology is consistent with the unfolded Brillouin zone (BZ) picture derived from a nonrealistic simple square or cubic Ir lattice. Through careful analysis, we determine that a superposition of the folded and unfolded band structures has been observed in the ARPES spectra obtained using photons in both ultraviolet and SX regions. To corroborate the physics deduced using low-energy ARPES studies, we propose to utilize SX-ARPES as a powerful complementary technique, as this method surveys more than one whole BZ and provides a panoramic view of electronic structures.

We present a detailed study on the 4f ground-state symmetry of the pressure-induced superconductor CeCu 2 Ge 2 probed by soft x-ray absorption and hard x-ray photoemission spectroscopy. The revised Ce 4f ground states are determined as | 7 = √ 0.45 |J z = ± 5 2 − √ 0.55 |∓ 3 2 with-type in-plane rotational symmetry. This gives an in-plane magnetic moment consistent with the antiferromagnetic moment as reported in neutron measurements. Since the in-plane symmetry is the same as that for the superconductor CeCu 2 Si 2 , we propose that the charge distribution along the c axis plays an essential role in driving the system into a superconducting phase.

We present clear experimental evidence for the momentum-dependent heavy fermionic electronic structures of the 4f -based strongly correlated system CeNi 2 Ge 2 by soft x-ray angle-resolved photoemission spectroscopy. A comparison between the experimental three-dimensional quasiparticle dispersion of LaNi 2 Ge 2 and CeNi 2 Ge 2 has revealed that heavy fermionic electronic structures are seen in the region surrounding a specific momentum. Furthermore, the wave vectors between the observed "heavy spots" are consistent with a result of neutron scattering reflecting magnetic correlations, which could be a trigger for the superconductivity in CeNi 2 Ge 2 .

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