Evidence of Two-Source King Plot Nonlinearity in Spectroscopic Search for New Boson.

Optical precision spectroscopy of isotope shifts can be used to test for new forces beyond the standard model, and to determine basic properties of atomic nuclei. We measure isotope shifts on the highly forbidden ^{2}S_{1/2}→^{2}F_{7/2} octupole transition of trapped ^{168,170,172,174,176}Yb ions. When combined with previous measurements in Yb^{+} and very recent measurements in Yb, the data reveal a King plot nonlinearity of up to 240σ. The trends exhibited by experimental data are explained by nuclear density functional theory calculations with the Fayans functional. We also find, with 4.3σ confidence, that there is a second distinct source of nonlinearity, and discuss its possible origin.

Evidence for Nonlinear Isotope Shift in Yb

We measure isotope shifts for five Yb^{+} isotopes with zero nuclear spin on two narrow optical quadrupole transitions ^{2}S_{1/2}→^{2}D_{3/2}, ^{2}S_{1/2}→^{2}D_{5/2} with an accuracy of ∼300 Hz. The corresponding King plot shows a 3×10^{-7} deviation from linearity at the 3σ uncertainty level. Such a nonlinearity can indicate physics beyond the Standard Model (SM) in the form of a new bosonic force carrier, or arise from higher-order nuclear effects within the SM. We identify the quadratic field shift as a possible nuclear contributor to the nonlinearity at the observed scale, and show how the nonlinearity pattern can be used in future, more accurate measurements to separate a new-boson signal from nuclear effects.

Multislip Friction with a Single Ion.

A trapped ion transported along a periodic potential is studied as a paradigmatic nanocontact frictional interface. The combination of the periodic corrugation potential and a harmonic trapping potential creates a one-dimensional energy landscape with multiple local minima, corresponding to multistable stick-slip friction. We measure the probabilities of slipping to the various minima for various corrugations and transport velocities. The observed probabilities show that the multislip regime can be reached dynamically at smaller corrugations than would be possible statically, and can be described by an equilibrium Boltzmann model. While a clear microscopic signature of multislip behavior is observed for the ion motion, the frictional force and dissipation are only weakly affected by the transition to multistable potentials.

Hexagonal GaN nanorod-based photonic crystal slab as simultaneous yellow broadband reflector and blue emitter for phosphor-conversion white light emitting devices.

We report a hexagonal GaN nanorod-based two-dimensional photonic crystal (PhC) slab for phosphor-conversion white light emitting devices analyzed by three-dimensional finite-difference time-domain simulation; this slab has a broad reflection band at yellow wavelength with low Fabry-Pérot background at normal incidence. For practical use as a wavelength-selective reflector, a buffer layer under the PhC slab is employed to sustain the nanorods in the PhC slab. However, we observed that the buffer layer placed below the slab destroys the broad reflection band due to evanescent coupling of electromagnetic field in the slab and the buffer layer. By introducing small-sized base pillars between the slab and the buffer layer, we could decouple the interaction between the slab and the buffer layer and maintain the broad reflection band without any unexpected dips. Since this GaN nanorod-based PhC slab is designed for practical light emitting devices by considering dielectric and transparent conducting layers, this structure is directly applicable for developing hybrid white light emitting devices having both an (active) blue-color-emitting nanorod emitters and a (passive) normal reflector of phosphor emission.

Melittin-induced alterations in morphology and deformability of human red blood cells using quantitative phase imaging techniques.

Here, the actions of melittin, the active molecule of apitoxin or bee venom, were investigated on human red blood cells (RBCs) using quantitative phase imaging techniques. High-resolution real-time 3-D refractive index (RI) measurements and dynamic 2-D phase images of individual melittin-bound RBCs enabled in-depth examination of melittin-induced biophysical alterations of the cells. From the measurements, morphological, intracellular, and mechanical alterations of the RBCs were analyzed quantitatively. Furthermore, leakage of haemoglobin (Hb) inside the RBCs at high melittin concentration was also investigated.