Demonstration of iodide-dependent UVA-triggered growth inhibition in Saccharomyces cerevisiae cells and identification of its suppressive molecules.

Upon white light illumination, the growth of the budding yeast Saccharomyces cerevisiae was extremely impaired only in the presence of iodide ions, but not fluoride, chloride and bromide ions. Action spectroscopy revealed that the maximum wavelength of the light is around at 373 nm, corresponding to the UVA region. Using a genetic approach, several genes, including OPY1, HEM1, and PAU11, were identified as suppressors of this growth inhibition. This iodide-dependent UVA-triggered growth inhibition method, along with its suppressive molecules, would be beneficial for understanding cell growth processes in eukaryotes and can be utilized for medium sterilization using UVA light.

Room-Temperature Type-II Multiferroic Phase Induced by Pressure in Cupric Oxide.

According to previous theoretical work, the binary oxide CuO can become a room-temperature multiferroic via tuning of the superexchange interactions by application of pressure. Thus far, however, there has been no experimental evidence for the predicted room-temperature multiferroicity. Here, we show by neutron diffraction that the multiferroic phase in CuO reaches 295 K with the application of 18.5 GPa pressure. We also develop a spin Hamiltonian based on density functional theory and employing superexchange theory for the magnetic interactions, which can reproduce the experimental results. The present Letter provides a stimulus to develop room-temperature multiferroic materials by alternative methods based on existing low temperature compounds, such as epitaxial strain, for tunable multifunctional devices and memory applications.

Magnetically Induced Polarization in Centrosymmetric Bonds.

We reveal the microscopic origin of electric polarization P[over →] induced by noncollinear magnetic order. We show that in Mott insulators, such P[over →] is given by all possible combinations of position operators r[over →][over ^]_{ij}=(r[over →]_{ij}^{0},r[over →]_{ij}) and transfer integrals t[over ^]_{ij}=(t_{ij}^{0},t_{ij}) in the bonds, where r[over →]_{ij}^{0} and t_{ij}^{0} are spin-independent contributions in the basis of Kramers doublet states, while r[over →]_{ij} and t_{ij} stem solely from the spin-orbit interaction. Among them, the combination t_{ij}^{0}r[over →]_{ij}, which couples to the spin current, remains finite in the centrosymmetric bonds, thus yielding finite P[over →] in the case of noncollinear arrangement of spins. The form of the magnetoelectric coupling, which is controlled by r[over →]_{ij}, appears to be rich and is not limited to the phenomenological law P[over →]∼ε_{ij}×[e_{i}×e_{j}] with ε_{ij} being the bond vector connecting the spins e_{i} and e_{j}. Using density-functional theory, we illustrate how the proposed mechanism works in the spiral magnets CuCl_{2}, CuBr_{2}, CuO, and α-Li_{2}IrO_{3}, providing a consistent explanation for the available experimental data.