1. Correlation-enhanced odd-parity inter-orbital singlet pairing of LiFeAs
R. Nourafkan, G. Kotliar, A.-M.S. Tremblay
Department of physics, Université de Sherbrooke
R. Nourafkan, G. Kotliar and A.-M.S. Tremblay, arXiv:
March meeting, Baltimore 2016

2. LiFeAs
Tc = 18K
Quasiparticle interference (AF) spin- fluctuation mediated mechanism M. P. Allan et al. Nat. Phys. 11, 177 (2015).
Polarized neutron diffraction: singlet pairing J. D. Wright et al.Rev. B 88, (2013). J. Brand, et al., Phys. Rev. B 89, (2014).
Long-lived moments: large U J. D. Wright, et al., Rev. B 88, (2013).
PRB. 88, (2013)

3. Objective: Mechanism Relative gap magnitude on Fermi surfaces
Angular dependence of gaps
Symmetry
ARPES
S. V. Borisenko, et al., Symmetry 4, 251 (2012)
K. Umezawa, et al. Phys. Rev. Lett. 108,
(2012).

4. Method Electronic structure: LDA + DMFT Pairing : AFM fluctuations
Eliashberg equations
2-Fe unit cell
Nonsymmorphic: anisotropic spin fluctuations
Odd = w.r.t mirror symmetry about the xy plane

5. Fluctuation mediated pairing
G. Esirgen and N. E. Bickers, Phys. Rev. B 57, 5376 (1998).
Z.Y. Meng, et al. Phys. Rev. Lett. 113,

6. Fluctuation mediated pairing
G. Esirgen and N. E. Bickers, Phys. Rev. B 57, 5376 (1998).
Z.Y. Meng, et al. Phys. Rev. Lett. 113,

7. Spin-charge fluctuations

8. Previous studies One Fe unit cell BCS approximation to Eliashberg
On the FS (not according to exp.) H. Miao, et al. Nat Commun 6, 7056 (2015).
Y. Wang, et al. Phys. Rev. B 88, (2013).
C. Platt, et al., Phys. Rev. B 84, (2011).
F. Ahn, et al., Phys. Rev. B 89, (2014).
Z. P. Yin, et al., Nat. Phys. 10, 845 (2014).
T. Saito et al., Phys. Rev. B 90, (2014).
T. Yamada, et al., Physical Society of Japan 83, (2014),

9. Odd-parity spin-singlet pairing
PREVIOUS STUDIES
J. Hu, Phys. Rev. X 3, (2013).
N. Hao et al., Phys. Rev. B 89, (2014).
Y. Wang, et al., Phys. Rev. Lett. 114, (2015).
Odd-parity spin-singlet pairing

10. RESULTS

11. Electronic Structure (LDA+DMFT: U=4 eV, J=0.8 eV)
See also: J. Ferber, Phys. Rev. B 85, (2012).
Z. P. Yin, et al., Nat. Mater. 10, 932 (2011).

12. Fermi Surfaces (LDA+DMFT)

13. Spin fluctuations

14. RPA Dressed Susceptibilities
xy-xy
xz-xz
xy-xz
Js = 0.1Us, Us = 2:4 eV on top
Js = 0.3Us, Us = 1:68 eV

15. Pairing

16. Pairing Interaction and Pairing field
xy-xy
xz-xz
xy-xz
T = 10 meV

17. Leading Pairing Channel
xy-xy
xz-xz
xy-xz
xy-yz
kz = 0

18. SC Gap Value
Gap equation: pairing channel and symmetry not magnitude

19. Conclusion
Hund’s coupling promotes intra-orbital dxz/yz and inter-orbital magnetic susceptibility.
Leads to pairing with inter-orbital odd parity under glide- plane symmetry dxy-dxz/yz singlet pairing (Eliashberg).
Predominantly conventional S+- symmetry (small x2-y2) (subdominant is S+- orbital antiphase pairing)
Intra- and inter-orbital pairing and anisotropic spin-charge fluctuations leads to consistency with experiments on gaps.
Predict : not C4 symmetric

20. Merci Thanks Questions?

21. Extra

22. Electronic Structure (LDA+DMFT: U=4 eV, J=0.8 eV)
See also: J. Ferber, Phys. Rev. B 85, (2012).
Z. P. Yin, et al., Nat. Mater. 10, 932 (2011).

23. Fe t2g character of Fermi Surfaces

24. Non-symmorphic effects