Probing thin-film YBa2Cu3O7−δ superconductors by second-harmonic generation with the use of femtosecond laser pulses

Jane K. Rice; S. W. McCauley; A. P. Baronavski; J. S. Horwitz; D. B. Chrisey

doi:10.1103/PhysRevB.47.6086

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Probing thin-film YBa2Cu3O7−δ superconductors by second-harmonic generation with the use of femtosecond laser pulses

Jane K. Rice, S. W. McCauley, A. P. Baronavski, J. S. Horwitz, D. B. Chrisey

DOI 10.1103/PhysRevB.47.6086 · Physical Review B

T1

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Abstract

High-temperature superconducting thin films of YBa2Cu3O7−δ are examined by measuring the second-harmonic generated (SHG) signal from an incident 60-fs laser pulse of 2.0 eV (620 nm) in air at room temperature. As oxygen stoichiometry is varied (0.00<δ<0.50), large changes in the SHG intensity are observed. The oxygen content of the films is independently determined by measuring (i) the c-axis lattice parameter derived from x-ray diffraction and (ii) the stoichiometry of the films determined by elastic backscattering spectrometry. We report a negative correlation of the SHG intensity with the c-axis parameter indicating that a known compression of the c axis leads to a larger SHG signal. An additional experiment in which the SHG intensity is monitored as a function of temperature (300–20 K) in vacuum is performed. A gradual increase of ∼50% in the SHG intensity is observed as the temperature is lowered, which can also be correlated to a decrease in the length of the c-axis parameter. Other experiments including rotation anisotropy and polarization of the incident and analyzer beams are also discussed.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	84	Pressure not reported	unknown
YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	57	Pressure not reported	unknown
YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	90	Pressure not reported	unknown
YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	60	Pressure not reported	unknown
La1.8Sr0.2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown