Pressure Dependence of Superconductivity of Iron Chalcogenides Shimizu group M1 Hidenori Fujita Contents • Introduction – High pressure – Superconductor – KxFe2-ySe2 • My experiment – High pressure experiment – Sample & Data • Conclusion & Future work introduction • High Pressure – 1 GPa = 10,000 atm http://www.jsanet.or.jp/qanda/text/q1_03. html ≅ 100,000 m (water depth) – 360 GPa ≅ center of the earth 100,000m http://www.spring8.or.jp/ja/news_publi cations/research_highlights/no_57/ introduction • High Pressure – Pressure can change crystal structure • atomic distance, structure type ….. etc. pressurization Molecule Insulator pressurization monatomic metal (金属単原子) Introduction • Superconductivity (SC)超伝 導 – Zero resistance – Meissner effect – Emerge at low temperature – Application http://www.kek.jp/ja/New sRoom/Highlights/201105 12133324/ • Superconducting magnet • SQUID • Transmission line …. etc. http://www.st-h.ed.jp/oldpage/clubpage/kaken/physics/katudou/tyoudenndou.html Introduction • Pressure dependence of SC – Transition temperature can change with pressure Journal of the Physical Society of Japan Vol. 78, No. 6, June, 2009, 063705 http://www.jst.go.jp/pr/anno unce/20080424/ Introduction • History of Tc – Highest ≅ 170 K (under high pressure in HgBa2Ca2Cu3O8+δ(Hg1223) ) – Iron based superconductor • Tc < 60 K • Chalcogenide & pnictide Introduction • KxFe2-ySe2 – Tc of KxFe2-ySe2 decrease by applying pressure – SC phase re-emerge at higher pressure (at 11GPa) doi:10.1038/nature10813 Motivation • Research…. – difference of sample (amount of K) • Previous research : K0.8Fe1.7Se2 – behavior at high pressure My experiment • High pressure experiment – Apply pressure with Diamond Anvil Cell My experiment • High pressure experiment – How to measure the electrical resistance My experiment • Sample 1 Run 1 – Property and condition K0.66Fe1.78Se2 (amount of K is few) Run 2 My experiment • Sample 1 – Results Run 1 Run 2 8 120 K0.66Fe1.78Se2 100 0.6 GPa 80 2.78 GPa 60 5.32 G K0.66Fe1.78Se2 6 3.39 GPa 40 R (ohm) R (ohm) Pa 7 Pa 7.16 G 5 8.08 GPa 4 10.19 G 3 Pa a 2 11.31 GP 20 1 12.49 G 0 0 6.27 GPa 0 50 100 150 T (K) 200 250 300 Pa 0 50 100 150 T (K) 200 250 300 My experiment • Sample 1 – Results 1.5 Pa G 9 0 .1 R (ohm) K0.66Fe1.78Se2 1 1.0 1G 11.3 Pa G 12.49 0.5 0.0 Pa 0 20 40 60 T (K) 80 100 My experiment • Sample 2 – Property and condition K0.8Fe2Se2 (original composition) My experiment • Sample 2 – Results My experiment • Sample 1 – Results 2.05 K0.8Fe2Se2 2.04 R (ohm) 2.03 11.10 GPa 2.02 2.01 2.00 1.99 1.98 0 5 10 15 T (K) 20 25 Sample 1 Sample 2 60 60 previous data my data 50 50 40 40 T (K) T (K) previous data my data 30 30 20 20 10 10 0 0 0 2 4 6 8 10 P (GPa) 12 14 16 0 2 4 6 8 P (GPa) 10 12 14 16 Conclusion & Future work • SC1-phase remains – SC2-phase didn’t appear • Future work – Change the amount of Fe – Continue to research at high pressure
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