Quasiparticle excitation in and around the vortex core of underdoped YBa_2Cu_4O_8 studied by site-selective NMR

We report a site-selective ^{17}O spin-lattice relaxation rate T_1^{-1} in the vortex state of underdoped YBa_2Cu_4O_8. We found that T_1^{-1} at the planar sites exhibits an unusual nonmonotonic NMR frequency dependence. In the region well outside the vortex core, T_1^{-1} cannot be simply explained by the density of states of the Doppler-shifted quasiparticles in the d-wave superconductor. Based on T_1^{-1} in the vortex core region, we establish strong evidence that the local density of states within the vortex core is strongly reduced.Comment: 5 pages, 3 figure

Microcavity lasing of optically excited cadmium sulfide thin films at room temperature

We report what is believed to be the first observation of lasing of an optically pumped thin CdS film formed by laser ablation on glass. Laser action is observed at room temperature, and the emission peak is at 501 nm. X-ray diffraction shows that the polycrystalline films are of wurtzite structure and have (002) preferred orientation. Fabry–Perot laser modes are spaced 16 nm apart, indicating a cavity length of 2.9 µm. The cavity is formed by consistently self-formed microcavities within the hexagonal lattice