Evidence for the strain critical point in high Tc superconductors

D. Di Castro; G. Bianconi; M. Colapietro; A. Pifferi; N. L. Saini; S. Agrestini; A. Bianconi

doi:10.1007/s100510070010

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Condensed Matter and Complex Systems

Eur. Phys. J. B 18, 617-624 (2000)
https://doi.org/10.1007/s100510070010

Evidence for the strain critical point in high T_c superconductors

D. Di Castro¹, G. Bianconi², M. Colapietro³, A. Pifferi⁴, N. L. Saini⁵, S. Agrestini⁵ and A. Bianconi⁵^a

¹ Dipartimento di Fisica, Università di Roma "La Sapienza", 00185 Roma, Italy
² Department of Physics, Notre Dame University, 46566 Indiana, USA
³ Dipartimento di Chimica, Università di Roma "La Sapienza", 00185 Roma, Italy
⁴ Istituto Strutturistica Chimica, Area della Ricerca, CNR, Monterotondo Stazione, Italy
⁵ Unità INFM and Dipartimento di Fisica, Università di Roma "La Sapienza", 00185 Roma, Italy

Corresponding author: ^a bianconi@superstripes.com

Received: 25 September 2000
Published online: 15 December 2000

Abstract

We report experimental evidence for the phase diagram of doped cuprate superconductors as a function of the micro-strain ε of the planar Cu-O bond length, measured by Cu K-edge EXAFS, and hole doping δ. The local lattice distortions are measured by EXAFS and the charge ordering is measured by synchrotron radiation diffuse X-ray diffraction. This phase diagram shows a QCP at P( $\varepsilon_{\rm c}\delta_{\rm c}$ ) where for $\varepsilon > \varepsilon_{\rm c}$ charge-orbital-spin stripes and free carriers co-exist. The superconducting phase occurs in the region of critical fluctuations around this QCP. The function $T_{\rm c}(\varepsilon, \delta)$ of two variables shows its maximum at the strain QCP. The critical fluctuations near this strain QCP give the self-organization of a metallic superlattice of quantum wires "superstripes" that favors the amplification of the critical temperature.