Institute of Physics Chinese Academy of Sciences IOP httppdaiphysutkedu Evolution of spin excitations in hightemperature FeAs based superconductors Chenglin Zhang Miaoyin Wang L W Harriger O Lipscombe ID: 830109
Download The PPT/PDF document "Pengcheng Dai The University of Tennesse..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Pengcheng Dai
The University of Tennessee (UT)
Institute of Physics, Chinese Academy of Sciences (IOP)
http://pdai.phys.utk.edu
Evolution of spin excitations in high-temperature FeAs-based superconductors
Slide2Chenglin Zhang, Miaoyin Wang, L. W. Harriger, O. Lipscombe
UT/ORNL
Meng Wang, Huiqian Luo, Shiliang LiIOP/BeijingJeff Lynn, Songxue ChiNIST center for neutron research
M. D. Lumsden, D. L. AbernathyHFIR and SNS, ORNLG. F. Chen, Nanlin Wang
IOP, BeijingD. T. Adroja, T. G. PerringISISTao Xiang (
IOP, Beijing),
Jiangping Hu (Purdue,
IOP, Beijing)
Slide3Phase diagrams of copper oxide and iron arsenide superconductors.
Mazin, Nature 464, 183 (2010).
Slide4Statement of the problem
How spin-waves in the parent compounds are modified as holes and electrons are doped into the parent compounds of high-
Tc superconductors?How superconductivity interacts with spin excitations? What spin excitations can tell us about gap symmetry?
Slide5Lattice structures of iron-based superconductors
LaFeAsO
1111Tn=150 K
BaFe2As2122Tn=150-200K
LiFeAs111
Tn ?
FeTe
11
Tn
=60 K
Slide6Localized magnets
What about
FeAs? What are the effective exchange couplings in FeAs?
Exchange couplings between local moments
Fermi surface
nesting in metals
La
2
CuO
4
Coldea
et al. PRL 86 5377 (2001)
J
= 112
meV
Slide7Spin structures of Fe-based parent compounds
CaFe2As2
122FeTe11
Slide8Spin structures of Fe-based parent compounds
(
Rb,K,Cs)Fe1.6Se2Tn=550 K, and parent compound is an insulator!
Slide9The Heisenberg Model
Slide10Low Temperature Ca(122)
Ca(122)
Jun Zhao et. al., Nature Physics 5, 555 (2009)
Slide11SJ1a = 49
SJ1b
= -5.7SJ2 = 19SJc = 5.3 meV
Magnetic exchange couplings in CaFe
2As2Jun Zhao
et al., Nature Physics 5, 555 (2009).
Slide12Wave vector dependence of spin-waves in
B
aFe2As2
Slide13Wave vector dependence of spin-waves in
B
aFe2As2
Slide14Model calculation
of spin-waves in
BaFe2As2SJ1a
= 59 meVSJ1b
= -9 meVSJ2= 13
meV
SJ3
= 2
meV
,
Similar to Jun Zhao
et al.,
Nature Physics 5, 555 (2009).
Slide15Comparison of Low T Exchange Couplings
J
1a
J
1b
J
2
J
c
BaFe
2
As
2
(7K)
59.2
-9.2
13.6
1.8
CaFe
2
As
2
(10K)
49.9
-5.7
18.9
5.3
Slide16Spin waves in FeTe
Slide17Spin waves in FeTe
SJ1a
= -17 meVSJ1b = -51
meVSJ2a=SJ2b = 22 meV
SJ3 = 6.8 meV
Lispcombe
et al.,
PRL (2011).
Slide18Spin structures of
Rb
0.8Fe1.6Se2 insulating parent compounds
Slide19Spin waves of insulating
Rb
Fe1.6Se2 along c-axis
Slide20Slide21Spin waves of
Rb
Fe1.6Se2 in the ab-plane
Slide22Slide23Slide24Model spin waves of
Rb
Fe1.6Se2
Slide25Slide26J
1a
J
1b
J
2
J
c
BaFe
2
As
2
(7K)
59.2
-9.2
13.6
1.8
CaFe
2
As
2
(10K)
49.9
-5.7
18.9
5.3
J
1a
J
1b
J
2
J
c
FeTe
(7K)
-17
-51
22
0
RbFe
1.6
As
2
(5 K)
-36
15
12 to 16
1.4
Bottom line, similarities between different Fe-based parent compounds
Slide27Why does this have anything to do with superconductivity?
Slide28Electron-doping hardly affects spin excitations in Fe-based superconductors
Slide29The effective of electron-doping on spin excitations
Slide30Low-energy spin excitations knows superconductivity, and can mediate pairing.
Slide31Summary
Spin waves in parent compounds have a common feature that is associated with J2 of the effective exchange coupling constant.
Electron-doping hardly affects the spin excitations in Fe-based superconductors.