A new method to induce molecular low bias negative differential resistance with multi-peaks

According to a first-principles study of the transport properties of two thiolated anthracene-9,10-diono molecules sandwiching ethyl, a new method to induce molecular low bias negative differential resistance with multi-peaks for strong n- or p-type molecules is proposed. The anthracene-9,10-diono molecule shows strong n-type characteristics when in contact with Au and Ag electrodes via a thiolate. The multiple negative differential resistance effect originated from the molecule-electrode couple is different between Ag and Au electrodes. Our investigations may promise potential for applications in molecular devices with low power dissipation and multifunction in the future.

The ferroelectric polarization of Y2CoMnO6 aligns along the b-axis: the first-principles calculations

Double-perovskite A2BB'O6 oxides with magnetic B and B' ions and E*-type antiferromagnetic order (E*-AFM, i.e. the ↑↑↓↓ structure) are believed to exhibit promising multiferroic properties, and Y2CoMnO6 (YCMO) is one candidate in this category. However, the microscopic origins for magnetically induced ferroelectricity in YCMO remain unclear. In this study, we perform detailed symmetry analysis on the exchange striction effect and lattice distortion, plus the first-principles calculations on YCMO. The E*-AFM state as the ground state with other competing states such as ferromagnetic and A-antiferromagnetic orders is confirmed. It is observed that the ferroelectricity is generated by the exchange striction associated with the E*-AFM order and chemically ordered Mn/Co occupation. Both the lattice symmetry consideration and first-principles calculations predict that the electric polarization aligns along the b-axis. The calculated polarization reaches up to 0.4682 μC cm(-2), mainly from the ionic displacement contribution. The present study presents a comprehensive understanding of the multiferroic mechanisms in YCMO and is of general significance for predicting emergent multiferroicity in other double-perovskite magnetic oxides.

Ferroelectricity driven magnetism at domain walls in LaAlO3/PbTiO3 superlattices

Charge dipole moment and spin moment rarely coexist in single-phase bulk materials except in some multiferroics. Despite the progress in the past decade, for most multiferroics their magnetoelectric performance remains poor due to the intrinsic exclusion between charge dipole and spin moment. As an alternative approach, the oxide heterostructures may evade the intrinsic limits in bulk materials and provide more attractive potential to realize the magnetoelectric functions. Here we perform a first-principles study on LaAlO₃/PbTiO₃ superlattices. Although neither of the components is magnetic, magnetic moments emerge at the ferroelectric domain walls of PbTiO₃ in these superlattices. Such a twist between ferroelectric domain and local magnetic moment, not only manifests an interesting type of multiferroicity, but also is possible useful to pursuit the electrical-control of magnetism in nanoscale heterostructures.