We review recent developments on Σ hypernuclear studies solving mysterious problems on the Σ hyperon behaviors in atoms, nuclei, and neutron-stars matter. To explain the data of Σ-atomic X-ray measurements and nuclear (π-, K+) spectra, we investigate Σ-nucleus potentials which are phenomenologically determined on the basis of several models; the repulsion and attraction in the potentials originate from Σ N interaction connected with flavor SU (3) nature and quark Pauli-forbidden states. We also discuss isoscalar and isovector components of the Σ-nucleus potential, considering solutions of the Σ narrow-width and 4Σ He bound-state problems.
Evaporation and drying are phenomena we see in our everyday life. They are also very important in industries. Though the subject is old, there are many questions which need to be answered from physics point of view. What determines the evaporation rate, how the structure evolves during evaporation, and how we can control the structure of the dried materials. Here I review recent works on these topics, focusing on the evaporation of droplets placed on a substrate. I discuss how the solvent evaporation is coupled with flow and shape change of the droplet, and how it affects the structure of the materials left on the substrate.
High temperature superconductivity appears in the cuprates when a spin order is destroyed, while the role of charge is less known. In this review, we describe our recent 63Cu-nuclear magnetic resonance study that discovered a long-range charge density wave (CDW) order in Bi2Sr2-x Lax CuO6+δ , setting in above the superconducting dome, under an in-plane field H||>10 T. The doping dependence of the onset temperature TCDW scales with the pseudogap temperature T *, which suggests that the T * is a high-temperature fingerprint of the CDW. The TCDW smoothly takes over the spin order temperature TN beyond a critical doping level at which superconductivity starts to emerge. These results provide new insights into the relationship between spin order, CDW and the pseudogap, and their connections to high-temperature superconductivity.
A new experiment to measure anomalous magnetic moment and electric dipole moment of muon is proposed by introducing a new muon beam with low emittance. The experiment will examine the possible deviation from the standard model of particle physics that was indicated in the previous measurement. The low-emittance muon beam is realized by re-accelerating nearly-stopped muons. An experiment to accelerate negative muonium ions to 90 keV was carried out with a radio frequency quadrupole cavity. This is a first ever demonstration of muon acceleration with RF field.
We introduce the Sachdev–Ye–Kitaev (SYK) model, which was introduced in a condensed matter theoretical context but has quickly drawn attention as one of the candidate theories for the non-gravity side of the holography principle, also known as the gauge/gravity duality. The model is known to satisfy the chaos bound of the Lyapunov exponent as in the case of certain black holes. We then review the holography principle and the SYK model and introduce the out-of-time order correlator (OTOC), which reveals the Lyapunov exponent of a quantum chaotic system. Finally, we explain our proposal for the experimental realization of the SYK model using cold atoms and molecules in an optical lattice in a way that OTOC is measurable. Experimental realization of theories that define quantum gravity would pave the way to the experimental study of quantum gravity, where condensed matter theorists and cold atom experimentalists can contribute.
In exotic superconductors including high-Tc cuprates, the interactions mediating electron pairs are widely considered to have a magnetic rather than the conventional electron-phonon origin. Interest in such exotic pairing was initiated by the 1979 discovery of heavy-fermion superconductivity in CeCu2Si2 . A hallmark of unconventional pairing is that the superconducting energy gap changes sign as a function of electron momentum, often leading to gap nodes. Here we report low-temperature specific heat, thermal conductivity, and magnetic penetration depth measurements in CeCu2Si2 , demonstrating the absence of gap nodes at any point on the Fermi surface. Moreover, electron-irradiation experiments reveal that the full-gap superconductivity is extremely robust against impurities, implying that there is no sign change in the gap function. Our findings reveal that, contrary to the long-standing belief, heavy electrons with extremely strong Coulomb repulsion can condense into non sign-changing and fully gapped s-wave superconducting state, which has an on-site attractive pairing interaction.