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Transient Reflectance Of Photoexcited Cd3As2, Christopher P. Weber, Ernest Arushanov, Bryan S. Berggren, Tahereh Hosseini, Nikolai Kouklin, Alex Nateprov
Transient Reflectance Of Photoexcited Cd3As2, Christopher P. Weber, Ernest Arushanov, Bryan S. Berggren, Tahereh Hosseini, Nikolai Kouklin, Alex Nateprov
Physics
We report ultrafast transient-grating measurements of crystals of the three-dimensional Dirac semimetal cadmium arsenide, Cd3As2, at both room temperature and 80 K. After photoexcitation with 1.5-eV photons, charge-carriers relax by two processes, one of duration 500 fs and the other of duration 3.1 ps. By measuring the complex phase of the change in reflectance, we determine that the faster signal corresponds to a decrease in absorption, and the slower signal to a decrease in the light's phase velocity, at the probe energy. We attribute these signals to electrons' filling of phase space, first near the photon …
Critical Point Pairs For Smectic-A* - Smectic-C* Phase Transitions., Ted Cassirer
Critical Point Pairs For Smectic-A* - Smectic-C* Phase Transitions., Ted Cassirer
Physics
Liquid crystals is a class of materials possessing properties from both solids and fluids. Similar to solids the molecules arrange themselves in some sort of order. In the liquid crystal state there are multiple phases, smectic being one of them. In a smectic liquid crystal the molecules are aranged (along $z$) in layers. Of the smectic liquid crystals there exists different phases. In the smectic-A (Sm-A) phase the avarage tilt is $0$ relative to $z$ and in the Smectic-C (Sm-A) phase the avarage tilt is non-zero relative to $z$. Normally the liquid crystal will transition between the two phases by …