Understanding the quantum critical behavior in the vicinity of a quantum phase transition remains one of the major challenges of condensed matter physics. In particular, the unconventional criticality, which cannot be explained by the spin fluctuation theory, has attracted much attention in strongly correlated electron systems. In this article, we review our recent findings of a novel quantum phase transition and superconductivity associated with the valence or orbital instability in 4f-electron systems revealed by high pressure experiments.
The resonance state localized on adsorbate has been shown to play a crucial role in photo-induced adsorbate dynamics. The observed non-equilibrium dynamics in hot-carrier induced desorption of CO on Cu (100) has been understood from the temperature- and mode-dependent friction coefficients deduced from the position and lifetime of the lowest-lying 2π resonance of CO molecule.
Intermolecular energy transfer is an essential dynamic process in photosynthesis and various energy-converting devices. So far, optical spectroscopy has been widely used to investigate the dynamic phenomenon. However, the spatial resolution of the conventional method is limited, and nanoscale spatial features in the energy transfer are still unknown. Here we demonstrate an atomic-scale investigation of energy transfers between a free-base phthalocyanine and a magnesium phthalocyanine (H2Pc and MgPc) using newly developed absorption/emission spectroscopy based on scanning tunneling microscopy (STM). A luminescence signal from H2Pc was detected while locally exciting a nearby MgPc with the tunnelling current of STM, clearly indicating an energy transfer from MgPc to H2Pc. The mechanism of the energy transfer is proven to be resonance energy transfer because charge transfer is prohibited by the energy-level alignment at the MgPc-H2Pc heterojunction. The fundamental insights into energy transfers pave the path for realizing excitonic circuits with molecular architectures on solid surfaces.
A few samples of double hypernuclei with two units of strangeness provided basic information on ΛΛ and Ξ N interaction. We expect a rapid progress in this field for not only experiment but also theory with the on-going E07 experiment at J-PARC.