Ideal Unconventional Weyl Point in a Chiral Photonic Metamaterial

Unconventional Weyl points (WPs), carrying topological charge 2 or higher, possess interesting properties different from ordinary charge-1 WPs, including multiple Fermi arcs that stretch over a large portion of the Brillouin zone. Thus far, such WPs have been observed in chiral materials and acoustic metamaterials, but there has been no clean demonstration in photonics in which the unconventional photonic WPs are separated from trivial bands. We experimentally realize an ideal symmetry-protected photonic charge-2 WP in a three-dimensional topological chiral microwave metamaterial. We use field mapping to directly observe the projected bulk dispersion, as well as the two long surface arcs that form a noncontractible loop wrapping around the surface Brillouin zone. The surface states span a record-wide frequency window of around 22.7% relative bandwidth. We demonstrate that the surface states exhibit a novel topological self-collimation property and are robust against disorder. This work provides an ideal photonic platform for exploring fundamental physics and applications of unconventional WPs.Comment: 6 pages, 4 figure

Predictive Bias Towards Neutral Stimuli in Non-Clinical Anxious Individuals

The relationship among predictive bias towards neutral stimuli, trait anxiety and gender in non-clinical individuals is studied. According to the scores on Trait Anxiety Inventory (TAI), 31 individuals are randomly selected from the highest 20% scorers as the high anxiety group, and 31 individuals from the lowest 20% scorers as the low anxiety group. Three types of stimulus situations are designed in the experiment, that is, 100% predictable, 50% predictable and unpredictable stimulus situations. MANOVA, which is performed on the reaction of high/low anxiety groups under three stimulus situations, shows that significant differences exist between high anxiety and low anxiety group under the 50% predictable and unpredictable conditions. Independent sample T test shows significant gender differences on predictive bias exist only in high anxiety group. Results of this study show that predictive bias towards neutral stimulus can be found in non-clinical anxious individuals and is significantly correlated with trait anxiety. In addition, predictive bias is more evident in high anxious female