Objectif
High-temperature superconductivity is achieved by chemically doping holes into the antiferromagnetic CuO2 planes of compounds such as La2CuO4. Recent neutron diffraction studies have provided evidence that the holes tend to segregate into periodically spaced domain walls that separate antiferromagnetic stripes of Cu spins. These phase separation effects are even more obvious in a related nonsuperconducting analog system, hole-doped La2CuO4. The present proposal is aimed at experimental and theoretical studies of the lattice and spin excitations (phonons and magnons) associated with these novel electronic correlations. The spin- and charge-density waves must induce new modes. A search of the additional lines associated with these new modes in the phonon frequency range at different temperatures will be performed with Raman (RLS) and Far Infrared (FIR) spectroscopies. The spin wave analysis will be used to interpret antiferromagnetic resonance (AFMR) and Brillouin light scattering (BLS) measurements of the magnetic excitations. All work will be performed on high quality single crystals. The most important result is a value of interaction constants between the charge, spins, and lattice systems that can obtain from RLS, BLS, FIR and AFMR measurements. The overall goal is to gain a better understanding of the connection between charge segregation and superconductivity in the copper-oxide superconductors.
Thème(s)
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52056 Aachen
Allemagne