Yeh, N.-C. and Beyer, A. D. and Teague, M. L. and Lee, S.-P. and Tajima, S. and Lee, S. I. (2010) Spectroscopic Evidence for Competing Order-Induced Pseudogap Phenomena and Unconventional Low-Energy Excitations in High-T_c Cuprate Superconductors. Journal of Superconductivity and Novel Magnetism, 23 (5). pp. 757-765. ISSN 1557-1939 http://resolver.caltech.edu/CaltechAUTHORS:20100701-083439398
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The low-energy excitations of cuprate superconductors exhibit various characteristics that differ from those of simple Bogoliubov quasiparticles for pure d_(x2−y2)-wave superconductors. Here, we report experimental studies of spatially resolved quasiparticle tunneling spectra of hole- and electron-type cuprate superconductors that manifest direct evidences for the presence of competing orders (COs) in the cuprates. In contrast to conventional type-II superconductors that exhibit enhanced local density of states (LDOS) peaking at zero energy near the center of field-induced vortices, the vortex-state LDOS of YBa_2Cu_3O_(7−δ) (Y-123) and La_(0.1)Sr_(0.9)CuO_2 (La-112) remains suppressed inside the vortex core, with pseudogap (PG)-like features at an energy larger (smaller) than the superconducting (SC) gap Δ_(SC) in Y-123 (La-112). Energy histograms of the SC and PG features reveal steady spectral shifts from SC to PG with increasing magnetic field H. These findings may be explained by coexisting COs and SC: For hole-type cuprates with PG above T_c, the primary CO gap (V_(CO)) is larger than Δ_(SC) and the corresponding COs are charge/pair-density waves with wave-vectors parallel to (π, 0)/(0,π). For electron-type cuprates without PG above T_c, V_(CO) is smaller than Δ_(SC) and the CO wave-vector is along (π,π). This CO scenario may be extended to the ARPES data to consistently account for the presence (absence) of Fermi arcs in hole- (electron)-type cuprates. Fourier transformation of the vortex-state LDOS in Y-123 further reveals multiple sets of energy-independent wave-vectors due to field-enhanced pair- and spin-density waves. These results imply important interplay of SC with low-energy collective excitations.
|Additional Information:||© 2010 Springer Science+Business Media, LLC. Received: 8 January 2010. Accepted: 11 January 2010. Published online: 29 January 2010 This work was jointly supported by the Moore Foundation and the Kavli Foundation through the Kavli Nanoscience Institute at Caltech, and the NSF Grant DMR-0405088. The work at Sogang University was supported by the Center of Superconductivity from the program of Acceleration Research of MOST/KOSEF of Korea and Special fund of Sogang University. The authors thank Dr. A.I. Rykov for growing the YBa2Cu3O7−δ single crystal used in this work and Professor S.A. Kivelson, Professor S.-C. Zhang, and Professor R.A. Klemm for useful discussions. ADB acknowledges the support of Intel Graduate Fellowship.|
|Subject Keywords:||Local density of states; Competing orders; Fermi arcs; Pseudogap; Cuprate superconductivity|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||05 Aug 2010 22:01|
|Last Modified:||26 Dec 2012 12:11|
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