Momentum-resolved resonant photoelectron spectroscopic study for 1T-TiSe2_2: Observation of negative q in the Fano resonance due to inter-atomic interaction in the valence band

The remarkable properties of (1T-)TiSe$_2$ among the transition metal dichalcogenides have attracted the attention of many researchers due to its peculiar behavior during the charge density wave (CDW) transition. Therefore, it is highly desirable to study its electronic structure down to the atomic orbitals. In the present research, we applied momentum-resolved resonant photoelectron spectroscopy to study TiSe$_2$ at the Ti2p-Ti3d absorption edge by using a momentum microscope, which can simultaneously detect the electronic states in a wide $(k_x,k_y)$ range. We have also used constant initial state (CIS) spectroscopy and density functional theory (DFT) calculations to reveal the hybridization between the Ti3d and Se4p orbitals within the valence band at the Gamma point at room temperature. In addition, an interesting result comes from our analysis of the CIS spectrum for the energy band located at a binding energy of 2 eV at the M-point. This band, mainly composed of the Se4p orbital, exhibited a Fano line profile at the Ti2p edge, with a negative value of the parameter "$q$". This is the first clear evidence of the inter-atomic interaction during the valence band photoelectron emission process. This behavior differs significantly from the standard resonant photoelectron emission, which usually involves intra-atomic interactions. It also differs from the multi-atom resonant photoelectron emission (MARPE) observed in the core-level photoelectron emission, as we focus on the photoelectron emission from the valence band in this research

The K computer Operations: Experiences and Statistics

AbstractThe K computer, released on September 29, 2012, is a large-scale parallel supercomputer system consisting of 82,944 compute nodes. We have been able to resolve a significant number of operation issues since its release. Some system software components have been fixed and improved to obtain higher stability and utilization. We achieved 94% service availability because of a low hardware failure rate and approximately 80% node utilization by careful adjustment of operation parameters. We found that the K computer is an extremely stable and high utilization system

Quantum key distribution at 1550 nm using a pulse heralded single photon source

Quantum key distribution with pulsed heralded single photon source was performed over 40 km of fiber for the first time to our knowledge. QBER was measured to be 4.23% suggesting security against unconditional attack