Normal state tunneling conductance of perovskite oxides: implications for high-Tc superconductors

Srikanth, H. ; Rajeev, K. P. ; Shivashankar, G. V. ; Raychaudhuri, A. K. (1992) Normal state tunneling conductance of perovskite oxides: implications for high-Tc superconductors Physica C: Superconductivity, 195 (1-2). pp. 87-92. ISSN 0921-4534

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/092145...

Related URL: http://dx.doi.org/10.1016/0921-4534(92)90078-Q

Abstract

We have investigated tunneling conductances in disordered, normally conducting perovskite oxides close to the metal-insulator transition. We show that the normal state tunneling conductance of perovskite oxides can be cast in a general form G(V)=G0[1+⋎V/Vn] with 1≥n≥0.5 and where V is an intrinsic energy scale. The exponent n graduall y increases from 0.5 to 1 as the metal-insulator (M-I) transition is approached. In the high-Tc Bi(2212) cuprates, the normally observed, linear G(V)(n=1) can be made sub-linear (n<1) by substitution of Ca with Y. From the similarity of the linear conductances, we suggest proximity to the M-I transition as a likely cause for this G(V)⊻ V dependence. In systems showing linear conductances (n⋍1), we find that ∂G/∂V⋍Gα0 with α⋍1 and the intrinsic energy scale V⋍25-75 meV in the different oxides investigated.

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