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Bi-Weekly Seminar

Intrinsic Electronic Instabilities, Magic Doping Levels, Wigner Lattices and High Temperature Superc(...)

by: Prof. Pei Hor

Date: Friday June 27, 2003

Time: 12:00 pm – 1:00 pm

Location: Houston Science Center – Building 593 — Room 102

Overview

We present a systematic study of the super-oxygenated La2-xSrxCuO4+ system. We show (i) that around room temperature, there are energetically favored intrinsic electronic instabilities of doped holes occur at some magic doping levels p = 1/N2 where p is the number of holes per copper atom and N = 2, 3, 4 | in the CuO2 plane, (ii) that at low temperature, there are only two intrinsic Tc's, Tc ~15K and Tc ~ 30K, in the under-doped La2-xSrxCuO4+. We argue that these instabilities are the manifestations of 2D electronic Wigner lattices and further show that they are intimately related to the occurrences of the intrinsic Tc ~15K and Tc ~ 30K superconducting transitions in La2-xSrxCuO4 single crystals. Based on (i), (ii) and our detailed studies of the far-infrared charge dynamics focusing on samples near N = 4, we find that only a very small (< 1 %) amount of the total holes participated in the nearly dissipationless normal state charge transport and superconductivity. These free carriers are riding on and massively screened by the rest of the holes organized in 2D Wigner lattice state. This unique composite system of charge carriers provides further insights into the understanding of the cuprate physics.

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