Crystal structure, thermal and spectral studies and growth of nonlinear optical L-lysinium fluoride crystal.

In current study properties of L-lysinium fluoride (L-Lys⋅HF) are determined by X-ray diffraction, infrared and Raman spectroscopy, SHG and by UV-vis transmittance spectrum measurement. L-Lys⋅HF (C6H15FN2O2), crystallizes in a monoclinic system with space group P21, a=5.464(1)Å, b=7.4717(15)Å, c=10.252(2)Å, α=γ=90°, ß=99.17(3)°, Z=2, ρc=1.336Mg/m(3), ρm=1.335(2)Mg/m(3). By means of evaporation method high quality L-Lys⋅HF single crystals are grown from aqueous solutions. L-Lys⋅HF crystal is transparent in the wavelength region 240-1100nm and it exhibits powder SHG efficiency 0.65 times that of potassium dihydrogen phosphate (KDP).

From a single-band metal to a high-temperature superconductor via two thermal phase transitions.

The nature of the pseudogap phase of cuprate high-temperature superconductors is a major unsolved problem in condensed matter physics. We studied the commencement of the pseudogap state at temperature T* using three different techniques (angle-resolved photoemission spectroscopy, polar Kerr effect, and time-resolved reflectivity) on the same optimally doped Bi2201 crystals. We observed the coincident, abrupt onset at T* of a particle-hole asymmetric antinodal gap in the electronic spectrum, a Kerr rotation in the reflected light polarization, and a change in the ultrafast relaxational dynamics, consistent with a phase transition. Upon further cooling, spectroscopic signatures of superconductivity begin to grow close to the superconducting transition temperature (T(c)), entangled in an energy-momentum-dependent manner with the preexisting pseudogap features, ushering in a ground state with coexisting orders.