R. Peng

Direct Observation of the Bandwidth Control Mott Transition in the NiS

The bulk electronic structure of NiS

_{2-x}

_{2-x}

Se

Se

_x

_x

Multiband System

is studied across the bandwidth-control Mott transition (BCMT) by soft X-ray angle-resolved photoemission spectroscopy. The microscopic picture of the BCMT in this multiband non-half-filled system is revealed for the first time. We show that Se doping does not alter the Fermi surface volume. When approaching the insulating phase with decreasing Se concentration, we observed that the Fermi velocity continuously decreases. Meanwhile, the coherent quasiparticle weight continuously decreases and is transferred to higher binding energies, until it suddenly disappears across the Mott transition. In the insulating phase, there is still finite spectral weight at the Fermi energy, but it is incoherent and dispersionless due to strong correlations. Our results provide a direct observation of BCMT, and unveil its distinct characters in a multiband non-half-filled system.

Electronic structure of the BaTi 2 As 2 O parent compound of the titanium-based oxypnictide superconductor

The electronic structure of BaTi2As2O, a parent compound of the newly discovered titanium-based oxypnictide superconductors, is studied by angle-resolved photoemission spectroscopy. The electronic structure shows multi-orbital nature and possible three-dimensional character. An anomalous temperature-dependent spectral weight redistribution and broad lineshape indicate the incoherent nature of the spectral function. At the density-wave-like transition temperature around 200 K, a partial gap opens at the Fermi patches. These findings suggest that BaTi2As2O is likely a charge density wave material in the strong interaction regime.

Temperature-induced orbital selective localization and coherent-incoherent crossover in single-layer FeSe / Nb : BaTiO 3 / KTaO 3

Iron chalcogenide superconductors are multiorbital materials with strong electron correlations. Here we use angle-resolved photoemission spectroscopy to study orbital dependent correlation effects in single-layer

Impurity scattering effects on the superconducting properties and the tetragonal-to-orthorhombic phase transition in FeSe

mathrm{FeSe}/mathrm{Nb}:{mathrm{BaTiO}}_{3}/{mathrm{KTaO}}_{3}

Electronic structure of the titanium-based oxypnictide superconductor Ba 0.95 Na 0.05 Ti 2 Sb 2 O and direct observation of its charge density wave order

, an iron chalcogenide superconductor with high interfacial superconductivity, nondegenerate electron pockets, and varied electron correlation compared with single-layer

Preparation of underdoped Bi2Sr2Ca2Cu3O10+δ single crystals

mathrm{FeSe}/{mathrm{SrTiO}}_{3}