1. Charge Kondo Effect and Superconductivity in Tl-Doped PbTe Y. Matsushita,et.al. PRL 94, 157002 (2005) T. A. Costi and V. Zlatic PRL 108, 036402 (2012) Hiroyasu MATSUURA and Kazumasa MIYAKE 81 (2012) 113705 KITAOKA.LAB. M １ MAKI SHOUTA

2. Contents History of Superconductivity Properties of PbTe Kondo effect Valence Skipper (ex:Tl) Experimental report Summary

3. History of Superconductivity under high pressure 0 50 100 150 200 SmO 0.9 F 0.11 FeAs LaO 0.89 F 0.11 FeAs LaOFeP Hg-Ba-Ca-Cu-O （） Tl-Ba-Ca-Cu-O Bi-Sr-Ca-Cu-O Y-Ba-Cu-O MgB 2 NbNb Ge Nb N NbC NbNb Pb high-T c cuprate metal iron-based system Transition temperature (K) 1900192019401960198020002020 Year HgHg La-Ba-Cu-O Discovery of superconducting phenomenon 1911 1986 High-T c cuprate superconductor 2006 Iron-based high-T c superconductor 77 163 1979 Heavy fermion superconductor CeCu 2 Si 2 heavy fermion system PuCoGa 5

4. Properties of PbTe NaCl structure, (space group Fm3m) Pb 2+ (6s 2 6p 2-2 ),Te 2- (5s 2 5p 4+2 ) PbTe : Eg(4.2K)=0.119eV PbTe : Eg(300K)=0.31eV Si : Eg(300K)=1.11eV Ge : Eg(300K)=0.67eV Tl-doping is hole doping to valence band 0.646nm

5. SC in Tl-Doped PbTe TcTc X= 0

6. Tl-Doped PbTe ρ0ρ0 X=1.3% X=0.8% X=0.4% X=0.3% X=0.2% X=0.1% X=0% ρ 0 ー ρ min ρ0ρ0 ρ min ρ 0 ∝ X → impurity density Increase of resistivity(ρ 0 ー ρ min) 《ｘ＞０．３》

7. Kondo effect The Kondo effect is caused by dilute magnetic impurities in a nonmagnetic host Fermi Sea Localized electron Conduction electron Spin singlet

8. Kondo effect The Kondo effect is caused by dilute magnetic impurities in a nonmagnetic host Fermi Sea Localized electron Conduction electron

9. Kondo effect The Kondo effect is caused by dilute magnetic impurities in a nonmagnetic host Fermi Sea Localized electron Conduction electron

10. Valence Skipper-Tl Energy Energy High Low Tl +1 Tl +2 Tl +3 Tl +1 ＜ Tl +3 ＜＜ Tl +2 6s6p Tl ・・・ Tl 1+ ・・・ Tl 2+ ・・・ Tl 3+ ・・・ Tl 1+ and Tl 3+ have no magnetic moment Why did we expect for Kondo-like behavior? -2e 0e0e

11. Experimental Report 1 Pr 1-x La x Pb 3 Pb1-xTlxTe It Isn’t based on ‘Spin-Kondo effect’ but ‘Chage Kondo effect’!! Ex)Kondo effect

12. Valence Skipper -Tl E n : total energy of n+ ionic state U n : effective intra-atomic Coulomb repulsion for n+ ionic state U(ns 1 ) < U(ns 0 ), U(ns 2 ) For valence skipper Electron in ns 1 state feels effectively intra-atomic attraction Negative U (attractive force between electrons) image

13. 6.46Å About 16Å Negative U Attractive force between electrons Charge fluctuation causes SC? X=1% 2-dimensions

14. Behavior of electron in Tl-Doped PbTe Negative U Attractive force between electrons Charge fluctuation causes SC? 0e0e 0e0e -2 e 6.46Å About 16Å image X>25%

15. Behavior of electron in Tl-Doped PbTe Negative U Attractive force between electrons Charge fluctuation causes SC? image X>25%

16. Summary PbTe is semi-conductor (narrow gap ). But Pb1- xTlxTe(X>0.3%) became SC. low-temperature resistivity upturn is observed by only Pb1- xTlxTe(X>0.3%). This behavior can be understood by ‘Charge Kondo effect’ So the theory predicts that ‘Charge Kondo effect’ relates to SC.

17. END