Recent research highlights

Local quasiparticle density of states and Fourier transformed local density of states in YBa₂Cu₃O_7-δ (Y-123).

Left image: The LDOS modulations of Y-123 at H = 5T and 6 K over a (22 x 29) nm² area, showing patterns associated with density-wave modulations and vortices (circled objects) for ω = (a) -9 meV ~ -Δ', (b) -23 meV ~ -Δ_SC, (c) -33 meV ~ -V_CO and (d) -53 meV. We note that the vortex contrasts are the most apparent at |ω| <~ Δ_SC and become nearly invisible for |ω| >>V_CO. The vanishing contrast at high energies may be due to the onset of Cu-O optical phonons (~ 50 meV for the cuprates) so that both the collective modes and quasiparticles become scattered inelastically. Right image: FT studies of the conductance maps of Y-123: |F(k,ω)| at H = 5T and ω = -12 meV. We identify three sets of ω-independent wave-vectors in addition to the reciprocal lattice constants and the (π,π) resonance: Q_PDW and Q_CDW along (π,0)/(0,π) and Q_SDW along (π,π), which are circled for clarity. For more information on the measurements in the hole-type cuprate Y-123, please see arxiv:0906.1776 and arxiv:0808.3016. For more information on the vortex-state measurements in the infinite-layer electron-type cuprate La_0.1Sr_0.9CuO₂ (La-112), please see arxiv:0809.0541.