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Enhanced Superconductivity in FeSe Monolayer on SrTiO3 Substrate

This study explores the enhanced superconductivity in FeSe monolayers on SrTiO3 substrates, investigating the effects of electron doping and charge transfer. Key findings include a critical temperature of ~65K. The research delves into interface atomic structures and the potential for achieving high Tc. The analysis also covers the thickness dependence of Tc, electron doping mechanisms, and the influence of bond-stretching vibrations on superconductivity.

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Enhanced Superconductivity in FeSe Monolayer on SrTiO3 Substrate

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  1. ‘Tc’ ~ 70 K: Fe-Based SC 200 Tc (K) 1UC FeSe on STO 100 ~ 70 K 55 K SmFeAsO 2012 LaFeAsO 2008 LaFePO 2006 0 1970 1980 1990 2000 2010 year

  2. FeSe Monolayer on a SrTiO3 Substrate Tc= 65±5 K (100 K ?) Se Fe Se SrTiO3 I. Mazin, Nature Mater. 14, 755 (2015). Review Dung-Hai Lee, Chin. Phys. B 24, 117405 (2015).

  3. FeSe Monolayer on a SrTiO3 Substrate Tc S. He, Q-K. Xue, X.J. Zhou et al., Nature Mater. 12, 605 (2013).

  4. FeSe Monolayer on a SrTiO3 Substrate Tc Tc = 108 K ?? Science Bulletin 60 (14), 1301-1304 (2015) S. He, Q-K. Xue, X.J. Zhou et al., Nature Mater. 12, 605 (2013). Z. Zhang, D.-L. Feng, Yayu Wang et al., arXiv: 1507.00129 J.F. Ge, Q.K. Xue et al., Nature Mater. 14, 285 (2015).

  5. Onset of Meissner effect in FeSe monolayer on Nb doped SrTiO3 substrate Z. Zhang, K.A. Moler, D.L. Feng, Yayu Wang, arXiv: 1507.00129; Science Bulletin 60 (14), 1301 (2015)

  6. Low-energymSR: Depth profile

  7. Thickness dependence of Tc for FeSe films on STO 80 60 Tc (K) 40 electron doping applying pressure Y. Mizuguchi et al., Appl. Phys. Lett. 93, 152505 (2008). Medvedev et al., Nature Materials 8, 630 (2009). Margadonna et al., Phys. Rev. B 80, 064506 (2009). 20 0 1UC 2UC 3UC 4UC 50UC ∞UC FeSe Thickness

  8. Pressure dependence of Tc for bulk FeSe J.P. Sun, T. Shibauchi et al., arXiv: 1512.06951; Nat. Commun. 7, 12146 (2016)

  9. Thickness dependence of Tc for FeSe films on STO 80 60 Tc (K) 40 electron doping applying pressure Y. Mizuguchi et al., Appl. Phys. Lett. 93, 152505 (2008). Medvedev et al., Nature Materials 8, 630 (2009). Margadonna et al., Phys. Rev. B 80, 064506 (2009). 20 0 1UC 2UC 3UC 4UC 50UC ∞UC FeSe Thickness

  10. Thickness dependence of Tc for FeSe films on STO 80 C. Tang, Q.-K. Xue et al., arXiv: 1509.08950; Phys. Rev. B92, 180507(R) (2015). 60 Y. Miyata, T. Takahashi et al., Nature Mater. 14, 775 (2015). Tc (K) C.H.P. Wen, D.-L. Feng et al., arXiv: 1508.05848; Nat. Commun. 7, 10840. 40 J. Shiogai et al., Nature Phys.12, 42 (2016). 20 0 1UC 2UC 3UC 4UC 50UC ∞UC FeSe Thickness

  11. SC of 2UC-FeSe (double-layer) on STO C. Tang, Q.-K. Xue et al., arXiv: 1509.08950; Phys. Rev. B92, 180507(R) (2015).

  12. Electron Doping into FeSe Films on STO K deposition Electric field SrTiO3 MgO Y. Miyata et al., Nature Mater. 14, 775 (2015). J. Shiogai et al., Nature Phys. 12, 42 (2016).

  13. Electron Doping into FeSe Films on STO K deposition Electric field Y. Miyata et al., Nature Mater. 14, 775 (2015). J. Shiogai et al., Nature Phys. 12, 42 (2016).

  14. Electron Doping into FeSe Films on STO K deposition C.-L. Song, Q.-K. Xue et al., arXiv: 1511.02007; Phys. Rev. Lett. 116, 157001 (2016). Y. Miyata et al., Nature Mater. 14, 775 (2015).

  15. Electron Doping into FeSe Films on STO I. Mazin, Nature Mater. 14, 755 (2015).

  16. FeSe Monolayer on SrTiO3: Interface Effect (1) Tc= 65±5 K Se Fe • Interface effects : • Electron transfer (doping) from O vacancies in the STO surface layer (?) • Doping/transfer is only to the bottom FeSe layer – Open question (?) Se SrTiO3 Se O O Dung-Hai Lee,Chin. Phys. B 24, 117405 (2015). Ti Review Ov O

  17. Interface Atomic Structure: 1UC-FeSe on STO F. Li, Q.-K. Xue et al., arXiv: 1512.05203. (State Key Labo. of Low-Dimensional QuantumPhysics, State Key Labo. of New Ceramics and Fine Processing, Tsinghua Univ.) Se O O Ti OV O Ti O O Sr TiO2-x

  18. FeSe Monolayer on SrTiO3: Charge Transfer (?) Hao Ding, Q-K. Xue et al., arXiv: 1603.00999; Phys. Rev. Lett. 117, 067001 (2016). J. Shiogai et al., Nature Phys. 12, 42 (2016).

  19. Enhanced Tc in Monolayer FeSe on STO 80 C. Tang, Q.-K. Xue et al., arXiv: 1509.08950; Phys. Rev. B92, 180507(R) (2015). 60 Y. Miyata, T. Takahashi et al., Nature Mater. 14, 775 (2015). Tc (K) C.H.P. Wen, D.-L. Feng et al., arXiv: 1508.05848; Nat. Commun. 7, 10840. 40 J. Shiogai et al., Nature Phys.12, 42 (2016). 20 0 1UC 2UC 3UC 4UC 50UC ∞UC FeSe Thickness

  20. FeSe Monolayer on a SrTiO3 Substrate Tc= 65±5 K Se Fe • Interface effects : • Electron transfer (doping) from O vacancies in STO (?) • An additional pairing channel from a coupling with the bond-stretchingO vibrations(W0~ 100 meV) in SrTiO3. Se SrTiO3 Se O O Dung-Hai Lee,Chin. Phys. B 24, 117405 (2015). Ti Review OV O

  21. FeSe on STO: Interface Effect (2) Dung-Hai Lee,Chin. Phys. B24, 117405 (2015).

  22. Proposed 1UC FeSe-TiO Complex Dung-Hai Lee,Chin. Phys. B 24, 117405 (2015).

  23. Enhanced Tc in Monolayer FeSe on STO 80 Tc = 60 K-class SC cannot be achieved by bulk and thicker films of FeSe. 60 Tc (K) 40 20 0 1UC 2UC 3UC 4UC 50UC ∞UC FeSe Thickness

  24. Summary of Tc and Gap in Bulk, Doped, and Monolayer FeSe S.N. Rebec, Z.-X.. Shen et al., arXiv: 1606.09358.

  25. Interface Atomic Structure: 1UC-FeSe on STO F. Li, Q.-K. Xue et al., arXiv: 1512.05203. aFeSe = 3.86 Å(3.76 Å) hSe= 1.31±0.01 Å (1.45 Å ) dSe-Ti = 3.58 Å hSeopt =1.38 Å a= 111.4°±0.9°(103.6°) a opt= 109.5° bulk FeSe

  26. FeSe Monolayer on a SrTiO3 (110) Substrate

  27. Small Electron Fermi Surface Pockets in FeSe L.P. Gor’kov, arXiv: 1510.03327; Phys. Rev. B 93, 060507 (2016).. B. Rosenstein et al., arXiv: 1601.07425. ● Validity of Migdal theorem - low EF The Fermi energy is small; EF ~ ħW0 EF ~ 60 meV ħW0 ~ 80-100 meV EF m* = m / [1 + m ln (EF/ħW0)]

  28. s-Wave SC Gap in Monolayer FeSe on STO Q. Fan, D.-L. Feng et al., Nature Phys. 11, 946 (2015).

  29. Exfoliated Monolayer Materials Anomalous charge transport

  30. Exfoliated Monolayer Materials “Magnetic graphene” MPS3(M: 3d-TM, Mn, Fe, Co, Ni) J.-G. Park (IBS-CCES, Seoul) Anomalous charge transport Bulk single crystal P.A. Joy & S. Vasudevan, PRB 46, 5425 (1992).

  31. Families of Iron-Based Superconductors Sr O V As Fe FeSe Sr4V2O6Fe2As2 LaFeAsO BaFe2As2 LiFeAs Tcmax = 55 K Tcmax = 39 K Tcmax = 22 K Tcmax = 8 K Tcmax = 38 K

  32. Families of Iron-Based Superconductors Sr O V As Fe FeSe Sr4V2O6Fe2As2 BaFe2As2 LaFeAsO LiFeAs KxFe2-ySe2 Ca4(Mg, Ti)3Fe2As2O8-y (Ca, La)Fe2As2 Tcmax = 55 K Tcmax = 39 K Tcmax = 22 K Tcmax = 8 K Tcmax = 38 K Tcmax = 55 K Tcmax = 45-49 K Tcmax = 48-49 K Tcmax = 47 K Already optimized !?

  33. Why is Fe-As(Se) unique ? Tc vs Bond Angle 1UC FeSe FeSe

  34. Tc vs Pn/Ch Height 1UC FeSe Y. Takano (NIMS)

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