Far-infrared investigation of the pseudogap in underdoped Pb{sub 2}Sr{sub 2}(Y/Ca)Cu{sub 3}O{sub 8}
- Department of Physics, Brock University, St. Catharines, Ontario, L2S 3A1 (CANADA)
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L2S 4M1 (CANADA)
- Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7 (CANADA)
- Department of Chemistry and Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, L2S 4M1 (CANADA)
The optical conductivity of underdoped Pb{sub 2}Sr{sub 2}(Y/Ca)Cu{sub 3}O{sub 8} has been obtained from 40 to 700thinspcm{sup {minus}1} via Kramers-Kronig analysis of the c-axis-polarized reflectance measured at temperatures between 10 and 300 K. In the normal state at the lowest and highest frequencies where it is least obscured by a large phonon contribution, the background c-axis optical conductivity of underdoped Pb{sub 2}Sr{sub 2}(Y/Ca)Cu{sub 3}O{sub 8} is observed to decrease systematically as the temperature is lowered from 300 to near 150 K. Upon lowering the temperature further, the optical conductivity remains constant until the superconducting transition temperature of 65 K is reached, whereupon, at the lowest frequencies only, a further depression is observed due to the removal of spectral weight into the superconducting condensate. The spectral weight which is redistributed into the {delta}-function condensate is estimated to derive from frequencies below 425thinspcm{sup {minus}1}. The depressed conductivity in the normal state is attributed to the formation of a pseudogap similar to that previously observed for underdoped YBa{sub 2}Cu{sub 3}O{sub 7{minus}y}, YBa{sub 2}Cu{sub 4}O{sub 8}, and La{sub 2{minus}x}Sr{sub x}CuO{sub 4}. The temperature dependence suggests that the pseudogap is fully formed at a temperature of the order 150 K. This corresponds closely to the temperature range where a change in slope of the ab-plane dc resistivity, and a decrease in the {sup 63}Cu NMR Knight shift are observed. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 632649
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 14 Vol. 56; ISSN 0163-1829; ISSN PRBMDO
- Country of Publication:
- United States
- Language:
- English
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