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Superconductivity in Ba 1 - X K X BiO 3 (BKBO)

Superconductivity in Ba 1 - X K X BiO 3 (BKBO). H. Matsuura and K. Miyake, J. Phys. Soc. Jpn. 81 (2012) 113705 C. Varma PRL (1988) Physica B 296 (2001) 112}119 W.E. Pickett JETP LETTERS VOLUME 70, NUMBER 5 K. N. Mikhalev, S. V. Verkhovski et.al

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Superconductivity in Ba 1 - X K X BiO 3 (BKBO)

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  1. Superconductivityin Ba1-XKXBiO3(BKBO) H. Matsuura and K. Miyake, J. Phys. Soc. Jpn. 81 (2012) 113705 C. Varma PRL (1988) Physica B 296 (2001) 112}119 W.E. Pickett JETP LETTERS VOLUME 70, NUMBER 5 K. N. Mikhalev, S. V. Verkhovski et.al K.Kumagai.et,alPhysica C 274 (l 997) 209-220 B. A. Baumert et.al. Barium Potassium Bismuth Oxide: A Review Kitaoka Lab. M1 Maki Shouta

  2. Contents • Introduction • Discussion -Ba1-XKXBiO3(BKBO)&BaBiO3(BBO) -Valence Skipper(VS) -VS relate to Superconductivity(SC) • My work • Summary 1 contents

  3. Introduction 1975 spin Tcmax~12K BaPbXBi1-XO3 1988 Spin + orbital TCmax~30K Ba1-XKXBiO3 phonon 1 Spin/valence Introduction

  4. Phase diagram in Ba1-XKXBiO3(BKBO) TC~30K at X=0.37 On set Off set No magnetic phase Low carrier=5×1021/cm3 K concentration X 2 Highest TC inoxide (without cuprate) introduction-BKBO

  5. Previous study of BKBO system BKBO Bi(Pb) 6s electrons 3 introduction-BKBO

  6. Parent material BaBiO3(BBO) H. Matsuura and K. Miyake, J. Phys. Soc. Jpn. 81 (2012) 113705 Band calculation 2+ Ba Bi4+ 2- Tilting and Breathing q Bi5+ Bi5+ Bi5+ Bi5+ Insulator Band gap 2eV metallic Bi3+ Bi3+ Bi3+ Bi3+ (6s)2 R charge density wave(CDW) state (6s)0 -2e 1 0e discussion-BKBO

  7. Crystal structure and distortion I2/m Pm3m R3 R3 T(K) solubility limit Ibmm Ibmm I2/m Pm3m Ba1-XKXBiO3(BKBO) 2 SC discussion-BKBO B. A. Baumertet.al. Barium Potassium Bismuth Oxide: A Review

  8. K doping effect in Ba1-XKXBiO3(BKBO) K dope ↓ Hole dope T(K) Pm3m solubility limit R3 Commensurate CDW 　→　Incommensurate CDW Ibmm I2/m Tcmax~30K on set off set Temperature↑ Kconcentration↑ and 3 X~0.37 suppression of structural distortion K concentration X discussion-BKBO

  9. Properties of Ba1-XKXBiO3(BKBO) Tilting & breathing Distortion No? Tilting T(K) Insulator Pm3m solubility limit Band gap Semiconductor Metallic R3 SC Structure Monoclinic Orthorhombic Cubic Ibmm I2/m × 0 0.5 0.1 0.37 4 discussion-BKBO

  10. Superconductivity gap in BKBO ＋ 2Δ/kTC=3.5±0.5 Full gap Week-coupling SC 5 discussion-BKBO

  11. BCS superconductivity? α TC∝ ∝(1/M)α M:isotope mass Physica B 296 (2001) 112}119 W.E. Pickett BCS × Low carrier=5×1021/cm3 high TC Electron-phonon interaction constant λ=0.2 6 New theory Valence Skipper relate to SC mechanism? discussion-BKBO

  12. What is Valence Skipper? induce negative U • Missing valence state (ns)1 For example Bi4+ [Xe](4f)14(5d)10(6s)1(6p)0 6s0 Bi3+ H. Matsuura and K. Miyake, J. Phys. Soc. Jpn. 81 (2012) 113705 [Xe](4f)14(5d)10(6s)2(6p)0 6s1 condition 7 6s2 Bi5+ [Xe](4f)14(5d)10(6s)0(6p)0 discussion-VS

  13. Theory of SC by VS C. Varma PRL(1988) U:intra-atomic repulsion parameter(Bi-Bi) t:hopping(Bi-O) V:intra-atomic repulsion parameter(Bi-O) Δ:level CDW AF Bi5+ Bi3+ SC SC t≪Δ eliminatethe flexibility of oxygen attraction-repulsion ccccccccc 9 discussion-BKBO x x

  14. 39K-NMR in Ba1-XKXBiO3(BKBO) 39K NMR half-height 3kHz. solubility limit Pm3m R3 X=0.5 X=0.4 Spectrum dose not change by T and K concentration Ibmm I2/m X=0.3 × K’s s electron Conduction band 9 ? JETP LETTERS VOLUME 70, NUMBER 5 K. N. Mikhalev, S. V. Verkhovski et.al discussion-BKBO

  15. 39K-NMR in Ba1-XKXBiO3(BKBO) JETP LETTERS VOLUME 70, NUMBER 5 K. N. Mikhalev, S. V. Verkhovski et.al X=0.3 X=0.3 T1Q-1(s-1) T1-1(s-1) X=0.4 X=0.4 X=0.5 X=0.5 T(K) 1000/T(1/K) Normal metallic x small → peak large T1-1(s-1) 137Ba/135Ba-NMR BaPbXBi1-XO3 T1Q-1 (137eQ/135eQ)=2.4 10 Valence fluctuation large T(K) T1e-1 (137γ/135γ)=1.2 (137T1-1/135T1-1)=2.1 at T＞80K eQ : Quadrupole moment discussion-BKBO γ : gyromagnetic ratio K.Kumagai.et,alPhysicaC 274 (l 997) 209-220

  16. Evidence of valence fluctuation X=0.3 T1Q-1(s-1) T(K) X=0.4 Pm3m solubility limit R3 X=0.5 1000/T(1/K) Ibmm I2/m Valence fluctuation is largest nearly Tcmax on set off set CDW 11 X~0.37 K concentration X discussion-BKBO

  17. Evidence of valence fluctuation X=0.3 T1Q-1(s-1) X=0.4 X=0.5 1000/T(1/K) Likely behavior Heavy electron system Cuprate CDW 12 X~0.37 K concentration X discussion-BKBO

  18. Bi(Pb) 6s electronsrelate to TC? on set off set 6s0.4 6s1 K concentration X Bi(Pb) 6s electrons 13 TCmax~50K is limit ? H. Matsuura and K. Miyake, J. Phys. Soc. Jpn. 81 (2012) 113705 discussion-BKBO

  19. Low carrier ~ 1018~19/cm3 My work image • Pb1-xTlxTe Tc(K) Tl+ Tl3+ TC~0.3K at X=0.3% -2e 0e X(at.%) 0.646nm NaCl structure (space group Fm3m) VS 1 My work

  20. Summary • Ba1-XKXBiO3(BKBO)reaches highest TCat X=0.37 irrespective of low carrier density. • Some results are consistent with BCS theory. • In Tcmax, valence fluctuation becomes maximum. Valence Skipper Bi3+ Bi5+ Tl1+ Tl3+ ⇔ ⇔ ? High TCSC 1 Summary

  21. Thank you for your listening END

  22. appendix

  23. Theory of SC by VS C. Varma PRL(1988) U:intra-atomic repulsion parameter(Bi-Bi) t:hopping(Bi-O) V:intra-atomic repulsion parameter(Bi-O) Δ:level CDW attraction-repulsion SC t≪Δ eliminatethe flexibility of oxygen 9 x discussion-BKBO ~ 1 – t4/z2|U|2V2 x

  24. Phase diagram in Ba1-XKXBiO3(BKBO) TC~30K at X=0.37 On set Off set No magnetic phase Low carrier K concentration X Bi(Pb) 6s electrons 2 Highest TC inoxide (without cuprate) intriduction-BKBO

  25. BCS superconductivity? α TC∝ ∝(1/M)α M:isotope mass Physica B 296 (2001) 112}119 W.E. Pickett × BCS theory Low-carrier high TC ? × Electron-phonon interaction constant λ=0.2 6 K concentration X New theory Valence Skipper relate to SC mechanism? discussion-BKBO

  26. Properties of Ba1-XKXBiO3(BKBO) Tilting & breathing Distortion U,V ⇒larger No? Tilting T(K) Insulator CDW Pm3m Band gap Semiconductor Metallic High TC??? R3 Structure Monoclinic Orthorhombic Cubic SC Ibmm ~ 1 – t4/z2|U|2V2 x I2/m × 0 0.5 0.1 0.37 13 discussion-BKBO

  27. Theory of SC by VS C. Varma PRL(1988) U:intra-atomic repulsion parameter(Bi-Bi) t:hopping(Bi-O) V:intra-atomic repulsion parameter(Bi-O) Δ:level CDW AF Bi5+ Bi3+ SC SC t≪Δ eliminatethe flexibility of oxygen attraction-repulsion ccccccccc 9 Heavy electron system discussion-BKBO x x

  28. Bi+3 Bi+5 q Bi5+ Bi5+ Bi5+ Bi5+ Bi3+ Bi3+ Bi3+ Bi3+ R charge density wave(CDW) state

  29. AF CDW AF AF + SC T (K) SC SC SC AF + SC Hole or electron dope (high TC SC) Pressure (heavy electron system) Heavy electron system ~ 1 – t4/z2|U|2V2 x x

  30. Phase Diagram of HF system TK ∝ W exp(-1/JcfD(εF)) TRKKY ∝ D(εF) Jcf2 AFM : antiferromagnetism HF: heavy fermion state QCP : quantumcritical point < ( ) γ＝ρ(f)J

  31. Summary 1.BKBO • SC ,which has VS in the origin ,appearing condition 1.nearing CDW (due to VS) 2.condition which chemical potential is pinned when VS is doped • How to rise the TC • 1.control CDW (structure) • 2.negative U become large 1 2.PbTlTe Summary

  32. 同位体効果 TC∝(1/M)αj

  33. Properties of Ba1-XKXBiO3(BKBO) K dope ↓ Hall dope Incommensurate CDW Tcmax=30K K substitution Temperature and on set off set suppression of structural distortion 2 K concentration X X~0.37 discussion-BKBO

  34. まとめ ・バレンススキッピング起源の超伝導 が出てきそうな所 １．バレンススキッパー起源のCDW付近 ２．バレンススキッパーをドープしていき、 　　化学ポテンシャルがピン止めされるところ ３．Ag酸化物の可能性 ・転移温度を上げる方法 1. 価数を制御する（→結晶構造の制御） 2. 波動関数の広がりが大きいと ネガティブ-Uが大きくなる。 周期表で下の元素を使う。

  35. What is charge density wave(CDW)? 5 Introduction-VS

  36. すこし理論の話 C. Varma PRL(1988) 引力-斥力変換の対応 酸素の自由度の消去 引力-斥力変換 二次摂動

  37. "Tilting" and "Breathing" distortion • "Breathing" • "Tilting" 5 Introduction-VS

  38. 同位体効果

  39. No-tilt sample (thin film)

  40. Tilting & breathing Distortion No? Tilting Insulator Band gap Semiconductor Metallic Monoclinic Structure Cubic Orthorhombic × 0 0.5 0.1 0.37 5 Summary

  41. Charge density X

  42. q Bi5+ Bi5+ Bi5+ Bi5+ Bi3+ Bi3+ Bi3+ Bi3+ R TC~11K ρ(μΩ) BaPb0.8Bi0.2O3

  43. BaBiO3(BBO)&Ba1-XKXBiO3(BKBO) • These material has Perovskite structure with “tilting” and “breathing”. • In addition to band structure calcuration , BBO is metallic.However BBO is insulater　with band gap 2eV. 5 Introduction-BKBO

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