ARPES studies on the pairing mechanism of iron-based superconductorsp

Hong DingHong Ding

Institute of Physics Chinese Academy of SciencesInstitute of Physics, Chinese Academy of Sciences

Hong Kong Forum of Physics, December 18, 2010

CollaboratorsARPES:

IOP: P. Richard, T. Qian, J. Dong, Y.-B. Huang, N. Xu, Y.-B. Shi, X.-P. Wang, Jon Bowen

Boston College: Y.-M. Xu, M. Neupane, Z.-H. Pan

Tohoku Univ.: K. Nakayama, T. Kawahara, K. Sugawara, T. Arakane, Y. Sekiba, A. Takayama S Souma T Sato T TakahashiTakayama, S. Souma, T. Sato, T. Takahashi

PSI: M. Shi, X.-Y. Cui，R. Elia, R. Milan

Renmin Univ.: Z.-H. Liu, S.-C. Wang

UVSOR: K. Terashima ALS: Alexei Fedorov

Theory:IOP: X. Dai, Z. Fang BC: Z. Wang Purdue: J.-P. Hu

Samples:

IOP: J.-L. Luo, N.-L. Wang, H.-Q. Luo, H.-H. Wen

Renmin Univ.: G.-F. Chen

Zhejiang Univ : L J Li G H Cao Z -A XuZhejiang Univ.: L. J. Li, G. H. Cao, Z.-A. Xu

UT: C.-L. Zhang, P.-C. Dai

Crystal structure of iron pnictides

１１

１１１１ １２２

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１１１１ １２２

U i lit iUniversality in Fermi surface topology

２１１１３ ３２２２５

& superconducting gap?

Phase diagram of Ba122 system

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Electron doping

Hole doping

M N l Xi 1005 2966 Electron-hole symmetry?M. Neupane et al., arXiv: 1005.2966

Fermi surface evolutionHeavily OD Slightly OD OPT UD

QAF QAF QAF QAF

H l d iTc = 3 K Tc = 22 K Tc = 37 K Tc = 26 K

Hole dopingParent OPTUD Heavily OD

QQAFQAF QAF

Electron dopingTc = 0 K Tc = 11 K Tc = 25 K Tc = 0 KTN = 135 K

5

Optimally hole doped Ba0.6K0.4Fe2As2 (Tc ~ 37K)

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Observation of superconducting gap

2/T 72/Tc ~ 7H. Ding et al., EPL 83, 47001 (2008)

A FS-dependent “kink” observed in SC state

P. Richard et al., PRL 102, 047003 (2009)

A.D.Christianson et al., Nature 456, 930 (2008) ~ 13 meV, similar to neutron resonance mode ~ 14 meV

Consistent with extended s± pairing p gmodel

M M Korshunov and I Eremin Phys Rev B 78 140509 (R) (2008)M.M. Korshunov and I. Eremin, Phys. Rev. B 78, 140509 (R) (2008)

Momentum dependence of the superconducting gap

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K. Nakayama et al., EPL 85, 67002 (2009)

J1 – J2 model predicts almost isotropic s± gap

Order parameters in momentum Space

Real space configurationof pairing symmetry

local interactionsJ1- J2

-

-- +++

-

coskxcosky, s±-wavpnictides: large J2 and FS nesting favor

cuprates: large J and FS topology favor cosk cosk )

K. Seo, A. B. Bernevig, J. Hu PRL 101, 206404 (2008)

cuprates: large J1 and FS topology favor coskx – cosky), d-wave

I. MazinD.H. Lee S. Graser

Most weak-coupling theories predict anisotropic s± gap

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PRB 79, 060502 (2009)EPL 85, 37005 (2009) NJP 11, 025016 (2009)The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

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when

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overdoped Ba0.3K0.7Fe2As2 (Tc ~ 20K)

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underdoped Ba0.75K0.25Fe2As2 (Tc = 26K)

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A distinct pseudogap emerges on the nesting FS region

Doping dependence of the SC gap in Ba1-xKxFe2As2

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Electron doped BaFe1.85Co0.15As2 (Tc = 25.5K)

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“111” - Electron doped NaFe0.95Co0.05As (Tc = 18K)

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“11” – FeTe1-xSex (Tc = 13 - 14K)

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FeTe0.7Se0.3 (Tc = 13K) FeTe0.5Se0.5 (Tc = 14K)The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

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K. Nakayama et al., PRL 105, 197001 (2010) New result

kz dependence of SC gaps Ba0 6K0 4Fe2As2kz dependence of SC gaps Ba0.6K0.4Fe2As2

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kz dependence of the SC gap h FS

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on the FS

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Fermi surface dependent nodeless superconducting gapThe image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

H. Ding et al., EPL 83, 47001 (2008) Y.-M. Xu et al., accepted by Nature Physics