Experimental Investigation of the Competing Orders and Quantum Criticality in Hole- and Electron-Doped Cuprate Superconductors

Yeh, N. -C.; Chen, C. -T.; Zapf, V. S.; Beyer, A. D.; Hughes, C. R.; Park, M. -S.; Kim, K. -H.; Lee, S. -I.

Experimental Investigation of the Competing Orders and Quantum Criticality in Hole- and Electron-Doped Cuprate Superconductors

Authors

Description

We investigate the issues of competing orders and quantum criticality in cuprate superconductors via experimental studies of the high-field thermodynamic phase diagrams and the quasiparticle tunneling spectroscopy. Our results suggest substantial field-induced quantum fluctuations in all cuprates investigated, and their correlation with quasiparticle spectra implies that both electron- (n-type) and hole-doped (p-type) cuprate superconductors are in close proximity to a quantum critical point that separates a pure superconducting (SC) phase from a phase consisting of coexisting SC and a competing order. We further suggests that the relevant competing order is likely a spin-density wave (SDW) or a charge density wave (CDW), which can couple to an in-plane Cu-O bond stretching longitudinal optical (LO) phonon mode in the p-type cuprates but not in the n-type cuprates. This cooperative interaction may account for the pseudogap phenomenon above Tc only in the p-type cuprate superconductors.
10 pages, 4 figures. Invited paper for the 2004 Taiwan International Conference on Superconductors