Evidence for a Metal-Insulator Transition in Overdoped Cuprates: New Raman Results
Transport properties play a major role in the characterization of correlated metals such as the cuprates. The usual dc and optical conductivity measurements, however, suffer from the missing momentum resolution in the strongly anisotropic CuO2 plane. The problem can be partially solved by using electronic Raman scattering. Here, the response is proportional to the conductivity. Additionally, different parts of the Fermi surface can be projected out by using polarized light. With this technique we study the electron dynamics in the normal state of cuprates over a wide range of doping. The strong anisotropy of the electron relaxation which evolves below a doping level of 0.22 holes/CuO2 is interpreted in terms of an unconventional metal-insulator-transition with an anisotropic gap. A phenomenology is developed which allows a quantitative understanding of the Raman results and provides a scenario which links single- and many-particle properties.
KeywordsRelaxation Rate Fermi Surface Doping Level Quantum Phase Transition Optimal Doping
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