Physics Colloquium, Manfred Fiebig, Department of Materials, ETH Zurich, Switzerland

Abstract:

Systems with strong electronic correlations lead to a fascinating variety of phenomena such as magnetic order, superconductivity, multiferroicity and much more. Although well-established non-optical characterization methods are at our disposal for investigating these states of matter, there are certain aspects of the ferroic state that these techniques cannot grasp.

In my talk, I will therefore focus on the interplay of ferroic order and light, emitted from intense laser sources. On the one hand, the laser light can be employed to detect ferroic states. Nonlinear optical techniques like doubling of the frequency of a light wave in a material (termed second harmonic generation, SHG) are extremely sensitive to ferroic states. They can detect even elusive varieties like multiferroic domains, improper ferroic order or novel types of ferroic order like ferrotoroidicity (a spontaneous order of magnetic whirls). On the other hand, the light can manipulate ferroic order, for example by promoting photoinduced phase transitions or the optically controlled reversal of a magnetic or electric order-parameter.