| Summary: | 碩士 === 國立臺灣師範大學 === 物理學系 === 104 === Since the high-temperature superconductor YBa2Cu3O7-δ(YBCO) was found, the modulation of its superconductivity became a popular topic among the field of materials science. Recent researches have revealed that different direction of the ferroelectric polarization in the multiferroics BiFeO3 (BFO) grown upon the superconductor YBCO leads to the variant critical temperature Tc of YBCO, and deducedthat interaction between ferroelectricity and superconductivity has abilities to suppress or raise superconducting properties of YBCO. To observe the superconducting states of YBCO near the domains (DMs) and the domain walls (DWs) of BFO, YBCO was grown on BFO. The electronic structures of the specimens YBa2Cu3O7-δ/ BiFeO3 (109°DWs) and YBa2Cu3O7-δ/ BiFeO3 (71°DWs) at the interface were measured by cross-sectional scanning tunneling microscopy (XSTM) directly in this study. Through the experimental result, how the superconducting state ofYBCO at the interface is influenced by the direction of ferroelectric polarization in BFO is revealed. The value of the superconducting energy gap 2Δis smaller when the direction of polarization points to YBCO than pointing away YBCO. In summary, the superconducting energy band gap of YBCO can be changed by the direction of ferroelectric polarization in BFO.
|
|---|
