Magnetic excitations investigated by ultrashort pulse excitation in high-Tc superconductors

Abstract

We have investigated the relaxation of elementary excitations in underdoped Bi2212 by ultrafast Raman spectroscopy. In x́ý symmetry, a broad feature has been observed around 2500 cm−1 in the Stokes side and assigned to B1g two-magnon peak. In investigating the power dependence of the broad feature, we observed a super-linear behavior in B1g symmetry, which is ascribed to the excess magnon population generated through the non-radiative relaxation across the CT gap. We observed a fast relaxation component around 0.4 ps and a long lifetime component greater than 20 ps for the B1g two-magnon peak.