Structural anomalies and multiferroic behavior in magnetically frustrated TbMn2 O5
Abstract:
The magnetostructural phase diagram of multiferroic TbMn2O 5 was investigated as a function of temperature and magnetic field by neutron diffraction. It was observed that dielectric and magnetic anomalies were associated with steps in the magnetic propagation vector, and in the structural parameters. The geometrically frustrated magnetic structure were found to be stabilized by "canted antiferroelectric" displacements of the Mn3+ ions. It was found that the Tb moments order ferromagnetically at low temperatures in an applied field, while the Mn magnetic structure is largely unchanged.Photo-induced chirality in a nonchiral crystal
Abstract:
Chirality, a pervasive form of symmetry, is intimately connected to the physical properties of solids, as well as the chemical and biological activity of molecular systems. However, inducing chirality in a nonchiral material is challenging because this requires that all mirrors and all roto-inversions be simultaneously broken. Here, we show that chirality of either handedness can be induced in the nonchiral piezoelectric material boron phosphate (BPO4) by irradiation with terahertz pulses. Resonant excitation of either one of two orthogonal, degenerate vibrational modes determines the sign of the induced chiral order parameter. The optical activity of the photo-induced phases is comparable to the static value of prototypical chiral α-quartz. Our findings offer new prospects for the control of out-of-equilibrium quantum phenomena in complex materials.