2001/08/15 by Yayu Wang, Zhu‐An Xu, Z. A. Xu +6 · 6 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic and transport properties of perovskites and related materials #Physics of Superconductivity and Magnetism #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.64.224519
published as Phys. Rev. B 64, 224519 (2001). · 10 pages, 10 figures
arxiv created 2001/08/15 · openalex publication_date 2001/11/21 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The diffusion of vortices down a thermal gradient produces a Josephson signal which is detected as a vortex Nernst effect. In a recent report by Xu et al. [Nature 406, 486 (2000)], an enhanced Nernst signal identified with vortex-like excitations was observed in a series of La_2\ensuremath-xSrxCuO4 (LSCO) crystals at temperatures 50--100 K above Tc. To pin down the onset temperature T_\ensuremathν of the vortexlike signal in the lightly doped regime (0.03<~x<~0.07), we have reanalyzed the carrier contribution to the Nernst signal in detail. By supplementing Nernst measurements with thermopower and Hall-angle data, we isolate the off-diagonal Peltier conductivity \ensuremathαxy and show that its profile provides an objective determination of T_\ensuremathν. With the results, we revise the phase diagram for the fluctuation regime in LSCO to accommodate the lightly doped regime. In the cuprate Bi2Sr_2\ensuremath-yLayCuO6, we find that the carrier contribution is virtually negligible for y in the range 0.4--0.6. The evidence of an extended temperature interval with vortexlike excitations is even stronger in this system. Finally, we discuss how T_\ensuremathν relates to the pseudogap temperature T* and the implications of strong fluctuations between the pseudogap state and the d-wave superconducting state.