Pressure effect on high-Tc cuprate superconductors 2010.06.16 Shimizu Lab. M1 KAMADA Yukihiro Contents Introduction • • • • About our group What’s pressure? Pressure effect on physical properties Motivation for high-Tc Experiment • About Diamond Anvil Cell (DAC) • My experiment Summary Introduction About our group Multiple extreme conditions Over 200 GPa High Pressure ～ 14 T Strong Magnetic Field Today’s main theme! Low Temperature ～ 15 mK Introduction What’s pressure? Changing physical properties 630 hPa （0.65 気圧） =63,000 Pa 1,013 hPa （1 気圧） =101,300 Pa 1 GPa = pressure @ trench × 10 = pressure @ surface × 10,000 = 1 万気圧 surface 200 m h k M G 2 MPa （20 気圧） =2,000,000 Pa continental shelf : 102 : 103 : 106 : 109 10,000 m 350 GPa （350 万気圧） trench 0.1 GPa （1000 気圧） =100,000,000 Pa Introduction Pressure effect on physical properties ※ Superconductivity ・ Electrical resistance is Zero ・ Meissner effect (perfect diamagnetism) pressure Able to change physical properties ・ Changing superconducting transition temperature (Tc) ・ etc… Kamerlingh Onnes, H., "The Superconductivity of Mercury." Comm. Phys. Lab. Univ. Leiden; Nos. 122 and 124, 1911. Introduction Motivation for high-Tc History of superconducting transition temperature (Tc) World record of high-Tc! Tc = 164 K @ 31 GPa L. Gao et al., Phys. Rev. B 50, 4260 (1994) Introduction Motivation for high-Tc HgBa2Cam-1CumO2m+2+d m = 3 is the best for high-Tc! My experiment d>0, supplying holes into the CuO2 layers Why? (not clear yet) c If we understand these reasons, we can make clear high-Tc system and realize higher Tc than now. a a 日本大学文理学部 マテリアルサイエンスにおける超高圧技術と高温超伝導研究 高橋 博樹 著 P.119 Introduction Motivation for high-Tc World record’s sample Not the best purity Not optimum dope under pressure → Sample with purity and optimum dope under pressure will be able to record higher Tc? Try to make a new world record! Experiment About Diamond Anvil Cell (DAC) 3 cm diamond gasket pressure medium sample 6 cm diamond Diamond Anvil Cell (DAC) ・culet (tip) size: 50 mm～1000 mm (1 mm) ・natural diamond ・synthetic diamond Merit: visible → X-ray small → set refrigerator Demerit: cannot use big samples ～ 350 GPa (≒ the center of the earth) Experiment My experiment Sample sample (high purity and under dope) 1.0 GPa Au wire Pt wire NaCl 70 mm SUS310S 150 mm 300 mm c-BN + epoxy ruby (pressure marker) 300 mm Highest Tc = 150 K @ 13 GPa Cooling with refrigerator and measuring electrical resistance Applying more pressure Sorry, but I’ll show you details on next semester’s presentation. Summary Pressure is very interesting method for changing physical properties. DAC is very useful for applying high pressure. My experiments • Measuring about Hg-1223’s pressure dependence of Tc • Highest Tc = 150 K @ 13 GPa Future → More experiments → New world record → Making clear high-Tc system about cuprate → Superconductivity @ room temperature pressure pleasure End Thank you for your attention!
© Copyright 2024 ExpyDoc
