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Superconductivity
in Ba1-XKXBiO3(BKBO)
Kitaoka Lab.
M1 Maki Shouta
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,al Physica C 274 (l 997) 209-220
B. A. Baumert et.al. Barium Potassium Bismuth Oxide: A Review
Contents
▪Introduction
▪Discussion
-Ba1-XKXBiO3(BKBO)&BaBiO3(BBO)
-Valence Skipper(VS)
-VS relate to Superconductivity(SC)
▪My work
▪Summary
1
contents
Introduction
1975
Tcmax~12K
spin
BaPbXBi1-XO3
1988
TCmax~30K
Spin
+
orbital
Ba1-XKXBiO3
phonon
1
Spin/valence
Introduction
Phase diagram in Ba1-XKXBiO3(BKBO)
40
Ba
Bi3+
Bi5+
O
Tc (K)
30
(a)
TC~30K at X=0.37
Ba1-xKxBiO3
電気抵抗率より決定
20
オンセット
On set
オフセット
Off set
10
No magnetic phase
Low carrier=5×1021/cm3
0
0
0.2
0.4
0.6
K濃度
K concentration
X x
Highest TC in oxide
(without cuprate)
2
introduction-BKBO
Previous study of BKBO system
BaPbO3
KBiO3
BaBiO3
50
Tc (K)
40
30
(Ba,Rb)BiO3
20
10
0
1
BKBO
(Ba,K)BiO3
(Ba,K)(Pb,Bi)O3
Ba(Pb,Bi)O3
(Sr,Rb)BiO3
(Sr,K)BiO3
(K,Bi)BiO3
(K,La)BiO3
Ba(Pb,Sb)O3
0.8
0.6
0.4
0.2
0
Bi（Pb)
6s軌道の電子数
Bi(Pb) 6s
electrons
3
introduction-BKBO
Parent material BaBiO3(BBO)
Band calculation
H. Matsuura and K. Miyake, J. Phys. Soc. Jpn. 81 (2012) 113705
Ba
2+
Ba
Bi3+
Bi4+
2-
Tilting
and
Breathing
Bi5+
O
Insulator
metallic
Band gap 2eV
charge density wave(CDW) state
q
Bi5+
-2e
Bi3+
0e
Bi5+
Bi3+
Bi5+
Bi3+
Bi5+
Ba2+
Bi3+ (6s)2
Bi4+(6s)1
Bi5+ (6s)0
Ionic radii (Å)
1.61
1.03
0.76
Bi3+
R
1
discussion-BKBO
Crystal structure and distortion
lattice
systems
T(K)
R3
I2/m
Ibmm
solubility limit
Pm3m
Space group
rhombohedra
l
R3
monoclinic
I2/m
orthorhombic
Ibmm
cubic
Pm3m
Lattice image
Ba1-XKXBiO3(BKBO)
SC
B. A. Baumert et.al. Barium Potassium Bismuth Oxide: A Review
2
discussion-BKBO
K doping effect in Ba1-XKXBiO3(BKBO)
K dope
↓
Hole dope
Pm3m
T(K)
solubility limit
R3
I2/m
40
Tc (K)
30
Ibmm
K+
Ba2+
Ionic radii (Å)
1.64
1.61
Commensurate CDW
→ Incommensurate CDW
Ba1-xKxBiO3
(a)
Tcmax~30K
電気抵抗率より決定
20
オンセット
on set
オフセット
off set
Temperature↑
and K concentration↑
10
X~0.37
0
0
0.2
0.4
K濃度 x
K concentration
X
0.6
suppression of structural distortion
3
discussion-BKBO
Properties of Ba1-XKXBiO3(BKBO)
solubility limit
Pm3m
T(K)
R3
Ibmm
I2/m
SC
Tilting
&
breathing
Distortion
Band gap
Insul
ator
Structure
Monoclinic
0
No?
Tilting
Semiconductor
Metallic
Orthorhombic
0.1
Cubic
0.37
0.5
×
4
discussion-BKBO
Superconductivity gap in BKBO
＋
2Δ/kTC =3.5±0.5
Full gap
Week-coupling SC
5
discussion-BKBO
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
New theory
Valence Skipper relate to SC mechanism?
6
discussion-BKBO
What is Valence Skipper?
• Missing valence state (ns)1
For example
Bi3+
Bi4+
Bi5+
[Xe](4f)14(5d)10(6s)2(6p)0
[Xe](4f)14(5d)10(6s)1(6p)0
[Xe](4f)14(5d)10(6s)0(6p)0
▪ induce negative U
6s0
6s1
6s2
H. Matsuura and K. Miyake, J. Phys. Soc. Jpn. 81 (2012) 113705
condition
7
discussion-VS
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
t≪Δ
eliminate the flexibility of oxygen
CDW
SC
x
attraction-repulsion
ccccccccc
Bi3+
AF
SC
Bi5+
9
xdiscussion-BKBO
Ba1-XKXBiO3(BKBO)
Pm3m
R3
39K
NMR
half-height 3kHz.
I2/m
Ibmm
solubility
limit
39K-NMR in
X=0.5
X=0.4
X=0.3
Spectrum dose not change
by T and K concentration
K’s s electron
×
?
Conduction band
9
JETP LETTERS VOLUME 70, NUMBER 5 K. N. Mikhalev, S. V. Verkhovski et.al
discussion-BKBO
39K-NMR in
Ba1-XKXBiO3(BKBO)
JETP LETTERS VOLUME 70, NUMBER 5 K. N. Mikhalev, S. V. Verkhovski et.al
X=0.3
T1Q-1(s-1)
T1-1(s-1)
X=0.3
X=0.4
X=0.5
X=0.5
T1-1(s-1)
T(K)
Normal
metallic
X=0.4
1000/T(1/K)
x small → peak large
BaPbXBi1-XO3
137Ba/135Ba-NMR
T1Q-1
T(K)
T1e
-1
(137eQ/135eQ)=2.4
(137γ/135γ)=1.2
eQ : Quadrupole moment
γ : gyromagnetic ratio
Valence fluctuation large
10
(137T1-1/135T1-1)=2.1 at T＞80K
K.Kumagai.et,al Physica C 274 (l 997) 209-220
discussion-BKBO
Evidence of valence fluctuation
X=0.3
T1Q-1(s-1)
Pm3m
T(K)
solubility limit
R3
I2/m
Ibmm
X=0.4
X=0.5
40
Ba1-xKxBiO3
(a)
1000/T(1/K)
Tc (K)
30
電気抵抗率より決定
20
Valence fluctuation is
largest nearly Tcmax
オンセット
on
set
CDW
オフセット
off set
10
X~0.37
0
0
0.2
0.4
K濃度 x
K concentration
X
0.6
11
discussion-BKBO
Evidence of valence fluctuation
T1Q-1(s-1)
X=0.3
X=0.4
X=0.5
1000/T(1/K)
40
Likely behavior
Ba1-xKxBiO3
(a)
Tc (K)
30
Heavy electron system
Cuprate
電気抵抗率より決定
20
オンセット
CDW
オフセット
10
X~0.37
0
0
0.2
0.4
K濃度 x X
K concentration
12
0.6
discussion-BKBO
Bi(Pb) 6s electrons relate to TC?
BaPbO3
KBiO3
BaBiO3
40
50
Ba1-xKxBiO3
(a)
40
電気抵抗率より決定
20
Tc (K)
Tc (K)
30
on set
オンセット
オフセット
off set
30
20
10
10
6s0.4
0
0
6s1
0.2
0.4
0.6
0
1
K concentration
K濃度 xX
(Ba,Rb)BiO3
(Ba,K)BiO3
(Ba,K)(Pb,Bi)O3
Ba(Pb,Bi)O3
(Sr,Rb)BiO3
(Sr,K)BiO3
(K,Bi)BiO3
(K,La)BiO3
Ba(Pb,Sb)O3
0.8
0.6
0.4
0.2
0
Bi（Pb)
6s軌道の電子数
Bi(Pb) 6s
electrons
TCmax~50K is limit ?
13
H. Matsuura and K. Miyake,
J. Phys. Soc. Jpn. 81 (2012) 113705
discussion-BKBO
Low carrier ~ 1018~19/cm3
Tc(K)
My work
Pb1-xTlxTe
image
X(at.%)
TC~0.3K at X=0.3%
VS
6s
NaCl structure
(space group Fm3m)
Tl+
Tl3+
・・・
・・・
Tl+
Tl3+
-2e
0e
1
My work
Ba
Bi3+
Summary
Bi5+
O
▪ Ba1-XKXBiO3(BKBO) reaches highest TC at 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
Thank you for your listening
END
appendix
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
t≪Δ
attraction-repulsion
eliminate the flexibility of oxygen
CDW
SC
~ 1 – t4/z2|U|2V2
x 9x
discussion-BKBO
Phase diagram in Ba1-XKXBiO3(BKBO)
40
BaBiO3
(a)
TC~30K at X=0.37
Ba1-xKxBiO3
40
電気抵抗率より決定
20
10
50
Tc (K)
Tc (K)
30
オンセット
On set
オフセット
Off set
No magnetic phase
0.2
30
0.4
0.6
K濃度
K concentration
X x
(Ba,Rb)BiO3
20
10
Low carrier
0
0
BaPbO3
KBiO3
0
1
(Ba,K)BiO3
(Ba,K)(Pb,Bi)O3
(Sr,Rb)BiO3
Ba(Pb,Bi)O3
(Sr,K)BiO3
(K,Bi)BiO3
(K,La)BiO3
Ba(Pb,Sb)O3
0.8
0.6
0.4
0.2
0
Bi（Pb)
6s軌道の電子数
Bi(Pb) 6s
electrons
Ba
Bi3+
Bi5+
O
Highest TC in oxide
(without cuprate)
2
intriduction-BKBO
BCS superconductivity?
α
TC∝
∝(1/M)α
M:isotope mass
Physica B 296 (2001) 112}119 W.E. Pickett
?
BCS theory
×
high TC
Ba1-xKxBiO3
(a)
30
×
Tc (K)
Low-carrier
40
Electron-phonon interaction
constant λ=0.2
電気抵抗率より決定
20
オンセット
オフセット
10
0
0
0.2
0.4
K濃度 x X
K concentration
0.6
6
New theory
Valence Skipper relate to SC mechanism?
discussion-BKBO
Properties of Ba1-XKXBiO3(BKBO)
U,V ⇒ larger
Pm3m
T(K)
R3
CDW
High TC???
I2/m
Ibmm
SC
~ 1 – t4/z2|U|2V2
x
Ba
Tilting
&
breathing
Distortion
Band gap
Insul
ator
Structure
Monoclinic
0
Bi3+
No?
Tilting
Semiconductor
Metallic
13
Orthorhombic
0.1
Bi5+
O
Cubic
0.37
0.5
×
discussion-BKBO
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
t≪Δ
Bi3+
Bi5+
eliminate the flexibility of oxygen
CDW
SC
x
attraction-repulsion
ccccccccc
AF
SC
9
Heavy electron system xdiscussion-BKBO
Bi+3
Bi+5
charge density wave(CDW) state
q
Bi5+
Bi3+
Bi5+
Bi3+
Bi5+
Bi3+
Bi5+
Bi3+
R
T
(K)
AF
AF
AF
++
SC
SC
SC
CDW
Hole or electron dope (high TC SC)
Pressure (heavy electron system)
SC
~ 1 – t4/z2|U|2V2
AF
SC
Heavy electron system x
x
Phase Diagram of HF system
TK
∝ W exp(-1/J cf D(εF))
TRKKY ∝ D(εF) Jcf2
AFM : antiferromagnetism
HF : heavy fermion state
QCP : quantum critical point
<
γ＝ρ(f)J
(
)
Summary
1.BKBO
SC ,which has VS in the
origin ,appearing condition
1.nearing CDW (due to VS)
Ba
Bi3+
Bi5+
O
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
同位体効果
TC∝(1/M)αj
Properties of Ba1-XKXBiO3(BKBO)
K dope
↓
Hall dope
+
K
Ba2+
Ionic radii (Å)
1.64
1.61
Incommensurate CDW
40
and
suppression of structural distortion
Bi5+
O
Tcmax=30K
電気抵抗率より決定
20
オンセット
on set
オフセット
off set
10
Ba
Bi3+
30
K substitution
Tc (K)
Temperature
Ba1-xKxBiO3
(a)
0
0
X~0.37
0.2
0.4
0.6
K濃度 x
K concentration
X
2
discussion-BKBO
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。
What is charge density wave(CDW)?
K+
Ba2+
Bi3+
Bi5+
Ionic radii (Å)
1.64
1.61
1.03
0.76
5
Introduction-VS
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
"Tilting" and "Breathing" distortion
▪ "Breathing"
▪"Tilting"
5
Introduction-VS
同位体効果
No-tilt sample (thin film)
Distortion
Tilting
&
breathing
Band gap
Insul
ator
Structure
Monoclini
c
0
No?
Tilting
Semiconductor
Metallic
Cubic
Orthorhombic
0.1
0.37
0.5
×
5
Summary
arge density
X
q
Bi5+
Bi3+
Bi5+
Bi3+
Bi5+
Bi3+
Bi5+
Bi3+
ρ(μΩ)
R
TC~11K
BaPb0.8Bi0.2O3
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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