1 / 13

Superconductivity in HgBa 2 Ca m-1 Cu m O 2m+2+δ (m=1,2, and 3) under quasihydrostatic pressures

Superconductivity in HgBa 2 Ca m-1 Cu m O 2m+2+δ (m=1,2, and 3) under quasihydrostatic pressures. L. Gao et al ., Phys. Rev. B 50 , 4260 (1994) C. Ambrosch-Draxl et al ., Phys. Rev. Lett. 92 , 187004 (2004). Shimizu-group Hanzawa Akinori. Introduction Cuprates series

zandra
Download Presentation

Superconductivity in HgBa 2 Ca m-1 Cu m O 2m+2+δ (m=1,2, and 3) under quasihydrostatic pressures

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Superconductivity in HgBa2Cam-1CumO2m+2+δ (m=1,2, and 3) under quasihydrostatic pressures L. Gao et al., Phys. Rev. B 50, 4260 (1994) C. Ambrosch-Draxl et al., Phys. Rev. Lett. 92, 187004 (2004) Shimizu-group Hanzawa Akinori

  2. Introduction Cuprates series HgBa2Cam-1CumO2m+2+δ CuO2 layer hole concentration Motivation Experiments Results & Discussions Summary Contents

  3. Cuprates series Most of high-temperature superconductors belong to cuprates series. La-Ba-Cu-O Tc= 32 K Tc= 40 K at 1.4 GPa Y-Ba-Cu-O Tc= 90 K Tc= 91 K at 1.8 GPa Tl-Ba-Ca-Cu-O Tc= 116 K Tc= 131 K at 7.5 GPa Hg-Ba-Ca-Cu-O Tc=134 K

  4. HgBa2Cam-1CumO2m+2+δ CuO2 layer For High Temperature cuprate Superconductor (HTS), CuO2 Layer is very important factor. m=1 m=2 m=3 http://hiroi.issp.u-tokyo.ac.jp/Pages/crystal%20gallery.html

  5. CuO2 layer Mott Insulator：Spins are alternately up and down. When coulomb repulsion for two electrons in a Cu is big, Electrons cannot move freely. antiferromagnetism Cu (Insulator) Carriers are doped metalization valence : +2 → +3 The origin of occurring superconductivity.

  6. hole concentration Solid Symbols(●, ▲, and ■) are optimally doped. Tc is the highest on optimally doped at ambient pressure. Tc vs n, where n is the number of carriers per CuO2 layer: △ Hg-1201, ○ Hg-1212, □ Hg-1223; solid symbols: samples used in this study. Temperature under dope over dope metal optimal dope Anti Ferro super-conductor △ ○ □ Carrier concentration

  7. Motivation High pressure is employed in the study of HTS. ・ Ceiling of Tc under high pressure ? ・ The cause for pressure-induced Tc increase in these optimally doped compounds ?

  8. Experiment Electrical resistance measurement Diamond Anvil Cell (DAC) diamond pressure medium : MgO insulator : Al2O3 + epoxy tungsten leads 0.3μm gasket : stainless sample (～300×300×25 ) ruby pseude four-lead resistance measurement 300μm

  9. Results Tc reached ・・・ Hg-1223 : 164 K at 31 GPa Hg-1212 : 154 K at 29 GPa Hg-1201 : 118 K at 24 GPa Tc＝164 K for Hg-1223 is the highest Tc in the world !

  10. Discussion 1 Si (semiconductor) Based on the results of・・・ ② carriers are doped “modulation doping” ① amount of oxygen change gap is narrow ③ electrical current flow ③ enhance more Tceffectively ② electrons move into another semiconductor gap is wide ① impurity is doped http://ja.wikipedia.org/wiki/%E5%8D%8A%E5%B0%8E%E4%BD%93

  11. Discussion 2 n vs P (theory) Tc vs P (experiment) outer plane inner plane Pressure perpendicular to the CuO2 layer moves a CuO2 layer close to another CuO2 layer. This effect induces a charge transfer.

  12. Discussion 3 Each phase purity by X-ray data. ～80% ～90% ～95% These samples were the highest purity at that time. Tc can raise much more ! Now the purity is more improved ･･･

  13. Summary ・ Universal large Tc enhancement was observed in HgBa2Cam-1CumO2m+2+δ. ・ A record high temperature of 164 K was reached in Hg-1223 at 31 GPa. ・ If we use high purity sample, Tc will make a record high.

More Related