H.Sakakibara et al., PRB-85, (2012) H.Sakakibara et al., PRB-89, (2014) MORISHITA Naoki Kusakabe laboratory M1 Division of Frontier Materials Science, Department of Material Engineering Science Graduate School of Engineering Science, Osaka University

 Introduction ◦ Superconductivity and superconductors  Theoretical models and approaches ◦ Conventional Modeling: The Single-orbital Model ◦ New Modeling : The Two-orbital model ◦ Sakakibara’s Rule  Summary Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 2/15

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 3/15 Introduction Phenomena ・ zero resistivity ・ Meissner effect ・ pinning effect ・ Josephson effect Temperature （ K ） Resistivity （ Ω ） Applications ・ power line ・ linear motor train ・ NMR/MRI ・ SQUID

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 4/15 Introduction Block layer(s) Buffer layer(s)

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 5/15 Introduction liquid nitrogen temperature 77(K)↓ 30(K) (1986) 90(K) (1987) 135(K) (1993) 153(K) (under high-pressure) (2013) 166(K)!? (under high-pressure) (2005)

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 6/15 Theoretical models and approaches Wannierized wave functionWhole structure on the Cu-O plane Conventional Modeling

 The Hubbard model(single-orbital) Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 7/15 Theoretical models and approaches 0.15 holes per site = optimal doping ( 最適ドープ ) Conventional Modeling We know much about superconductivity of this model.

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 8/15 Theoretical models and approaches H.Sakakibara et al., PRB-85, (2012) Conventional Modeling

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 9/15 Theoretical models and approaches ◆:Theory (single-orbital model) H.Sakakibara et al., PRB- 89, (2014) ● ● Conventional Modeling

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 10/15 Theoretical models and approaches New Modeling H.Sakakibara et al., PRB-85, (2012)

 Two-orbital model Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 11/15 Theoretical models and approaches Bad for S.C. ／ (^o^) ＼ Good for S.C. ＼ (^o^) ／ New Modeling

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 12/15 Theoretical models and approaches H.Sakakibara et al.,PRB- 89, (2014) New Modeling

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 13/15 Theoretical models and approaches H.Sakakibara et al.,PRB- 89, (2014) (a)Theory(b)Experiment New Modeling

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 14/15 Theoretical models and approaches Our aim Large(→bad nesting…)Small(→good nesting!)

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ. 15/15 Thank you for your kind attention!

Kusakabe lab., Graduate School of Engineering Science, Osaka Univ.