M1 colloquium
M. Hiraishi et al., Nature Phys. 10, 300-303 (2014)
S_IIMURA et al., Nature Commun. 3, 943 (2012)
S_IIMURA et al., Phys. Rev. B. 88, 060501(R) (2013)
Kitaoka Lab.
Takayoshi SHIOTA

Introduction
Superconductivity(properties, history)
 Iron-based superconductor
(structure, phase diagram)
 LaFeAs(O1-xFx)




Results
LaFeAs(O1-xHx)
Experiment
Theoretical calculation
Summary
introduction
Zero resistivity
Perfect diamagnetism
http://allnewscience.blogspot.jp/2010/07/anti-gravity.html
http://teachers.web.cern.ch/teachers/archiv/HST2001/accelerators/superconductivity/superconductivity.htm
introduction
1911
Transition temperature (K)
200
metal
heavy fermion system
high-Tc cuprate
163
iron-based system
150
Discovery of
superconducting
phenomenon
Hg-Ba-Ca-Cu-O
（under high pressure ）
Hg-Ba-Ca-Cu-O
Tl-Ba-Ca-Cu-O
1979
Heavy fermion
superconductor
Bi-Sr-Ca-Cu-O
100
Y-Ba-Cu-O
1986
77
50
MgB2
Hg
Pb
La-Ba-Cu-O
PuCoGa5
NbGe
Nb
NbC
NbN CeCu2Si2
LaFeAsO0.89F0.11
LaFePO
0
1900 1920 1940 1960 1980 2000 2020
Year
High-Tc cuprate
superconductor
SmFeAsO0.9F0.1
2006
Iron-based high-Tc
superconductor
introduction
Pn
Fe
Iron Pnictides
LnFePnO
Ae4M2O6Fe2Pn2
Ln =La, Ce, Pr,
Nd, Gd, Tb, Dy,
Er, Y
AeFe2Pn2
AFePn
Ae =Ba, Sr,
Ca, Eu
A =Li, Na
O
M
Ae
Ln
Ae
A
FeCh
Ae2Fe4Ch5
Iron Chalcogenides
introduction
Pn
hPn
hPn ~ 1.38Å
Fe
α
Regular tetrahedron
α = 109.5ﾟ
Mizuguchi et al. Supercond. Sci. Technol. 23 (2010) 054013.
C. H. LEE et al. J. Phys. Soc. Jpn., Vol. 77, No. 8
introduction
LnFeAsO
introduction
TS：Structural transition temperature
T< TS
LnFeAsO
introduction
TT<T
<TNS
TN：Magnetic transition temperature
Stripe antiferromagnetic state
LnFeAsO
introduction
TN：Magnetic transition temperature
T< TN
LnFeAs(O1-xFx)
O2- = F- + eElectron doping
introduction
Tc：Superconducting transition temperature
T< Tc
LnFeAs(O1-xFx)
O2- = F- + eElectron doping
Superconducting state
(cooper-pair)
The correlation between
magnetic/structural
fluctuation
and superconductivity?
introduction
Phase diagram
Band structure
E
εF
hole
(π,0)
Fermisurface
Electron
doping
k
Electron doping
Nesting weak
electron
introduction
AF：Antiferromagnetism
SC：Superconductivity
Nesting weak
The disappearance of SC
had not been confirmed
Problem
O2- → FLow solubility limit of F- in O2-
O2 - → HHydrogen behaves H- in oxide
Electron dopant as flourine
High solubility limit!
Results
x=0.08
Tc=29K
x
 x=0.01
kink in resistivity due to
structural or magnetic transition
was seen around 150K
 x≧0.08
zero resistivity due to
superconductivity
Tc =29K
Tc =18K
Results
x=0.36
Tc =36K
x
 x=0.08~0.53
zero resistivity due to
superconductivity
Results
x=0.08
Tc=29K
n=2
Fermi liquid
state
x=0.36
Tc =36K
x
0.04<x<0.21：
first dome(SC1)
0.21<x<0.53：
second dome(SC2)
n=1
Non-Fermi
liquid state
ρρ0  AT n
Electronic state around x=0.40
is different from x=0.10
Why??
Results
Weaker α-β nesting
γ
α
x = 0.08
x=0.21
Stronger γ-β/β-β nesting
x=0.40
β
Results
Χα-β
Χγ-β
0≦x≦0.05
Large χα-β (π,0) induces
stripe-type AFM ordering
0.05<x<0.20
Spin fluctuations at Q ∼ (π,0)
develop
x~0.20
Switching from χα-β to χγ -β
0.20<x
χγ –β becomes stronger
with increasing x
Nesting weak
x
Results
Electron
doping
Results
Hole
doping
These experiment and theoretical
calculation were performed in
LaFeAs(O1-xHx).



Two-dome superconducting phases (SC1,SC2) were found.
The ground state is an antiferromagnetic ordering
in 0≦x<0.05 (AFM1) and 0.40≦x≦0.51 (AFM2) .
These results suggest that superconductivity relates to
magnetism.