"Light-Matter Interaction in Charge Density Waves" by Anshul Kogar (MIT)

Wednesday, February 27, 2019 - 4:00pm to 5:00pm
Condensed Matter Physics Seminar

Light-Matter Interaction in Charge Density Waves

Anshul Kogar

Massachusetts Institute of Technology

When electrons in a solid are excited with light, they can alter the free energy landscape and access regions that are beyond reach in thermal equilibrium. This accessibility becomes of importance in the presence of phase competition, when one state of matter is favored over another by only a small energy scale that, in principle, is surmountable with light. In this talk, I will discuss a few of our recent ultrafast electron diffraction results on charge density wave (CDW) materials showing that, under far-from-equilibrium conditions, we observe strong evidence for topological defects. These defects are crucial in explaining how the amplitude of the CDW recovers well before long-range phase coherence. I will also show that in certain CDW materials, these defects can be manipulated with light to form metastable structures. Lastly, I will show that light can be used to unleash a CDW that is not present in equilibrium.


4-330 PAB