Progress in Superconductivity and Cryogenics (한국초전도ㆍ저온공학회논문지)

The Korean Society of Superconductivity and Cryogenics (한국초전도저온학회)
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A review on angle resolved photoemission spectroscopy studies of Fe-based superconductors

  • Seo, J.J. (Department of Physics, Yonsei University) ;
  • Kim, C. (Department of Physics, Yonsei University)
  • Received : 2014.06.19
  • Accepted : 2014.06.27
  • Published : 2014.06.30
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Abstract

Since the discovery of iron-based superconductors in 2008, extensive and intensive studies have been performed to find the microscopic theory for the high temperature superconductivity in the materials. Electronic structure is the basic and essential information that is needed for the microscopic theory. Experimentally, angle resolved photoelectron spectroscopy (ARPES) is the most direct tool to obtain the electronic structure information, and therefore has played a vital role in the research. In this review, we review what has been done so far and what is needed to be done in ARPES studies of iron-based superconductors in search of the microscopic theory. This review covers issues on the band structure, orbital order/fluctuation, and gap structure/symmetries as well as some of the theories.

Keywords

References

  1. P. J. Hirschfeld et al, "Gap symmetry and structure of Fe-based superconductors," Rep. Prog. Phys., vol. 74, pp. 124508, 2011. https://doi.org/10.1088/0034-4885/74/12/124508
  2. I. I. Mazin et al, "Unconventional Superconductivity with a sign Reversal in the Order Parameter of $LaFeAsO_{1-x}F_x$," Phys. Rev. Lett., vol. 101, pp. 057003, 2008. https://doi.org/10.1103/PhysRevLett.101.057003
  3. F. F. Tafti et al, "Sudden reversal in the pressure dependence of $T_c$ in the iron-based superconductor $KFe_2As_2$," Nat. Phys., vol. 9, pp. 349, 2013. https://doi.org/10.1038/nphys2617
  4. Ch. Platt et al, "Mechanism for a pairing state with time-reversal symmetry breaking in iron-based superconductors," Phys. Rev. B, vol. 85, pp. 180502, 2012. https://doi.org/10.1103/PhysRevB.85.180502
  5. S. Graser et al, "Near-degeneracy of several pairing channels in multiorbital models for the Fe pnictides," New J. Phys, vol. 11, pp. 025016, 2009. https://doi.org/10.1088/1367-2630/11/2/025016
  6. R. Thomale et al, "Exotic d-Wave Superconducting state of Strongly Hole-Doped $KxBa_{1-x}Fe_2As_2$," Phys. Rev. Lett., vol. 107, pp. 117001, 2011. https://doi.org/10.1103/PhysRevLett.107.117001
  7. K. Suzuki et al, "Spin fluctuations and unconventional pairing in $KFe_2As_2$," Phys. Rev. B, vol. 84, pp. 144514, 2011. https://doi.org/10.1103/PhysRevB.84.144514
  8. S. Maiti et al , "Evolution of the superconducting state of Fe-based compounds with doping," Phys. Rev. Lett., vol. 107, pp. 147002, 2011. https://doi.org/10.1103/PhysRevLett.107.147002
  9. R. Fernades et al, "Suppression of superconductivity by Neel type magnetic fluctuations in the iron pnictides," Phys. Rev. Lett., vol. 110, pp. 117004, 2013. https://doi.org/10.1103/PhysRevLett.110.117004
  10. W. C. Lee et al, "Pairing state with a time-reversal symmetry breaking in FeAs-based superconductors," Phys. Rev. Lett., vol. 102, pp. 217002, 2009. https://doi.org/10.1103/PhysRevLett.102.217002
  11. V. Stanev et al, "Three-band superconductivity and the order parameter that breaks time-reversal symmetry," Phys. Rev. B, vol. 81, pp. 134522, 2010. https://doi.org/10.1103/PhysRevB.81.134522
  12. Ch. Platt et al, "Mechanism for a pairing state with time-reversal symmetry breaking in iron-based superconductors," Phys. Rev. B, vol. 85, pp. 180502, 2012. https://doi.org/10.1103/PhysRevB.85.180502
  13. P. Dai et al, "Magnetism and its microscopic origin in iron-based high temperature superconductors," Nat. Phys., vol. 8, pp. 709, 2012. https://doi.org/10.1038/nphys2438
  14. S. Liang et al, "Nematic state of Pnictides Stabilized by interplay between Spin, Orbital and Lattice Degreeds of Freedom," Phys. Rev. Lett., vol. 111, pp. 047004, 2013. https://doi.org/10.1103/PhysRevLett.111.047004
  15. W. Lv et al, "Orbital ordering and unfrustrated (${\pi}$,0) magnetism from degenerate double exchange in the iron pnictides," Phys. Rev. B, vol. 82, pp. 045125, 2010. https://doi.org/10.1103/PhysRevB.82.045125
  16. W.-G. Yin et al, "Unified picture for magnetic correlations in iron-based superconductors," Phys. Rev. Lett., vol. 105, pp. 107004, 2010. https://doi.org/10.1103/PhysRevLett.105.107004
  17. R. Fernades et al, "Preemptive nematic order, pseudogap, and orbital order in the iron pnictides," Phys. Rev. B, vol. 85, pp. 024534, 2012. https://doi.org/10.1103/PhysRevB.85.024534
  18. M. Yi et al, "Symmetry breaking orbital anisotropy observed for detwinned $Ba(Fe_{1-x}Co_x)_2As_2$ above the spin density wave transition," Proc. Natl. Acad. Sci., vol. 108, pp. 6878, 2011. https://doi.org/10.1073/pnas.1015572108
  19. M. Yi et al, "Electronic reconstruction through the structural and magnetic transitions in detwinned NaFeAs," New J. Phys., vol. 14, pp. 073019, 2012 https://doi.org/10.1088/1367-2630/14/7/073019
  20. Y. Zhang et al, "Symmetry breaking via orbital-dependent reconstruction of electronic structure in detwinned NaFeAs," Phys. Rev. B, vol. 85, pp. 085121, 2012. https://doi.org/10.1103/PhysRevB.85.085121
  21. J. Paglione et al, "High-temperature superconductivity in iron-based mateirals," Nat. Phys., vol. 6, pp. 1759, 2010.
  22. C.-H. Lee et al, "Effect of Structural Parameters on Superconductivity in Fluorine-Free $Ba(Fe_{1-x}Co_x)_2As_2$ (Ln=La, Nd)," J. Phys. Soc. Jpn., vol. 77, pp. 083704, 2008. https://doi.org/10.1143/JPSJ.77.083704
  23. Y Mizuguchi et al, "Anion height dependence of $T_c$ for the Fe-based superconductor," Superconductor Science and Technology, vol. 23, pp. 05401, 2010.
  24. Kazuhiko Kuroki et al, "Pnictogen height as a possible switch between high-$T_c$ nodeless and low-$T_c$ nodal pairings in the iron-based superconductors," Phys. Rev. B, vol. 79, pp. 224511, 2009. https://doi.org/10.1103/PhysRevB.79.224511
  25. J. Zhao et al, "Structural and magnetic phase diagram of $CeFeAsO_{1-x}F_x$ and its relation to high-temperature superconductivity," Nat. Mater., vol. 7, pp. 953, 2008. https://doi.org/10.1038/nmat2315
  26. http://www.physics.berkeley.edu/research/lanzara/research/pnictide.html
  27. H. Kontani et al, "Origin of orthombic transition, magnetic transition, and shear-modulus softening in iron pnictide superconductors: Analysis based on the orbital fluctuations theory," Phys. Rev. B, vol. 84, pp. 024528, 2011. https://doi.org/10.1103/PhysRevB.84.024528
  28. H. Kontani et al, "Orbital fluctuation theory in iron-based superconductors: s++-wave superconductivity, structure transition , and impurity-induced nematic order," Sol. Stat. Comm., vol. 152, pp. 718, 2012. https://doi.org/10.1016/j.ssc.2012.01.012
  29. T. Saito et al, "Orbital fluctuation theory in iron pnictides: Effects of As-Fe-As bond angle, isotope substitution, and $Z_2$ orbital pocket on superconductivity," Phys. Rev. B, vol. 82, pp. 144510, 2010. https://doi.org/10.1103/PhysRevB.82.144510
  30. Y. Ono et al, "Structural transition, ferro-orbital order and its fluctuation-mediated S++-wave superconductivity in iron pnictides," Sol. Stat. Comm., vol. 152, pp. 701, 2012. https://doi.org/10.1016/j.ssc.2012.01.017
  31. S. Kasahara et al, "Electronic nematicity above the structural and superconducting transition in $BaFe_2(As_{1-x}P_x)_2$," Nature, vol. 486, pp. 7403, 2012.
  32. M. Daghofer et al, "Orbital-weight redistribution triggered by spin order in the pnictides," Phys. Rev. B, vol. 81, pp. 180514, 2010. https://doi.org/10.1103/PhysRevB.81.180514
  33. M. Yoshizawa et al, "Anomalous elastic behavior and its correation with superconductivity in iron-based superconductor $Ba(Fe_{1-x}Co_x)_2As_2$," Mod. Phys. Lett. B, vol. 26, pp. 1230011, 2012.
  34. D. Liu et al, "Electronic origin of high-temperature superconductivity in single-layer FeSe superconductor," Nat. Comm., vol. 3, pp. 1946, 2012.
  35. L. X. Yang et al, "Surface and bulk electronic structures of LaFeAsO studied by angle-resolved photoemission spectroscopy," Phys. Rev. B, vol. 82, pp. 104519, 2010. https://doi.org/10.1103/PhysRevB.82.104519
  36. S. V. Borisenko et al, "Superconductivity without Nesting in LiFeAs," Phys. Rev. Lett., vol. 105, pp. 067002, 2010. https://doi.org/10.1103/PhysRevLett.105.067002
  37. A. Damascelli ,"Probing the Electronic Structure of complex systems by ARPES," Physica Scripta., T109, 2004.
  38. I. I. Mazin et al, "Superconductivity gets an iron boost," Nature, vol. 464, pp. 183, 2010. https://doi.org/10.1038/nature08914
  39. M.M. Korshunov et al, "Theory of magnetic excitations in iron-based layered superconductors," Phys. Rev. B, vol. 78, pp. 140509 2008. https://doi.org/10.1103/PhysRevB.78.140509
  40. A. V. Chubukov, "Pairing mechanism in Fe-based superconductors," Annu Rev. Condens. Mat. Phys., vol. 3, pp. 57, 2012. https://doi.org/10.1146/annurev-conmatphys-020911-125055
  41. F. Wang et al ,"The electron-pairing mechanism of iron-based superconductors," Science, vol. 332, pp. 200, 2011. https://doi.org/10.1126/science.1200182
  42. Q. Si et al, "Strong correlations and magnetic frustration in the high $T_c$ iron pnictides," Phys. Rev. Lett., vol. 101, pp. 076501, 2008.
  43. Q. Si et al," Correlation effects in the iron pnictides," New J. Phys., vol. 11, pp. 045001, 2009. https://doi.org/10.1088/1367-2630/11/4/045001
  44. K. Seo et al, "Pairing symmetry in a two-orbital exchange coupling model of oxypnictides," Phys. Rev. Lett., vol. 101, pp. 206404, 2008. https://doi.org/10.1103/PhysRevLett.101.206404
  45. F. Ma et al,"Arsenic-bridged antiferromagnetic superexchange interactions in LaFeAsO," Phys. Rev. B, vol. 78, pp. 224517, 2008 https://doi.org/10.1103/PhysRevB.78.224517
  46. M. M. Qazilbash et al, "Electronic correlations in the iron pnictides," Nat. Phys., vol. 5, pp. 647, 2009. https://doi.org/10.1038/nphys1343
  47. T. Terashima et al., "Fermi surface and mass enhancement in $KFe_2As_2$ from de Haas-Van Alphen effect measurements," J. Phys. Soc. Jpn., vol. 79, pp. 053702, 2010. https://doi.org/10.1143/JPSJ.79.053702
  48. K. Nakamura et al, "Ab initio derivation of low-energy model for iron-based superconductors LaFeAsO and LaFePO," J. Phys. Soc. Jpn., vol. 77, pp. 093711, 2008. https://doi.org/10.1143/JPSJ.77.093711
  49. D. S. Inosov et al, "Crossover from weak to strong pairing in unconventional superconductors," Phys. Rev. B, vol. 83, pp. 213520, 2011.
  50. Z. P. Yin et al, "Kinetic frustration and the nature of the magnetic and paramagnetic states in iron pnictides and iron chalcogenides," Nat. Mater., vol. 10, pp. 932, 2011. https://doi.org/10.1038/nmat3120
  51. C. He et al, "Electronic-structure-driven magnetic and structure transitions in superconducting NaFeAs single crystals measured by angle-resolved photoemission spectroscopy," Phys. Rev. Lett., vol. 105, pp. 117002, 2010. https://doi.org/10.1103/PhysRevLett.105.117002
  52. A. Nicholson et al., "Role of degeneracy, hybridization, and nesting in the properties of multi-orbital systems," Phys. Rev. B, vol. 84, pp. 094519, 2011. https://doi.org/10.1103/PhysRevB.84.094519
  53. M. Y. Wang et al, "Spin waves and magnetic exchange interactions in insulating $Rb_{0.89}Fe_{1.58}Se_2$," Nat. Comm., vol. 2, pp. 580, 2011. https://doi.org/10.1038/ncomms1573
  54. M. S. Liu et al, " Nature of magnetic excitations in superconducting $BaFe_{1.9}Ni_{0.1}As_2$." Nat. Phys., vol. 8, pp. 376, 2012. https://doi.org/10.1038/nphys2268
  55. H. Park et al., "Magnetic excitation spectra in $BaFe_2As_2$: A two-particle approach within a combination of the density functional theory and the dynamical mean-field theory method," Phys. Rev. Lett., vol. 107, pp. 137007, 2011. https://doi.org/10.1103/PhysRevLett.107.137007
  56. H. Gretarsson et al, "Revealing the dual nature of magnetism in iron pnictides and iron chalcogenides using x-ray emission spectroscopy," Phys. Rev. B, vol. 84, pp. 100509, 2011. https://doi.org/10.1103/PhysRevB.84.100509
  57. F. Bondino et al, "Evidence for Strong Itinerant Spin Fluctuations in the Normal State of $CeFeAsO_{0.89}F_{0.11}$ Iron-Oxypnictide Superconductors," Phys. Rev. Lett., vol. 101, pp. 267001, 2008. https://doi.org/10.1103/PhysRevLett.101.267001
  58. M. Yi et al, "Electronic structure of the $BaFe_2As_2$ family of iron-pnictide superconductors," Phys. Rev. B, vol. 80, pp. 024515, 2009. https://doi.org/10.1103/PhysRevB.80.024515
  59. W. Malaeb et al, "Abrupt change in the energy gap of superconducting $Ba_{1-x}K_xFe_2As_2$ single crystals with hole doping," Phys. Rev. B, vol. 86, pp. 165117, 2012. https://doi.org/10.1103/PhysRevB.86.165117
  60. N. Xu et al, "Effects of Ru substitution on electron correlations and Fermi-surface dimensionality," Phys. Rev. B, vol. 86, pp. 064505, 2012. https://doi.org/10.1103/PhysRevB.86.064505
  61. Z. R. Ye et al, "Orbital selective correlations between nesting/scattering/Lifshitz transition and the superconductivity in $AFe_{1-x}Co_xAs$(A=Li, Na)," arXiv 1303.0682v1.
  62. S. V. Borisenko et al, "Superconductivity without nesting in LiFeAs," Phys. Rev. Lett., vol. 105, pp. 067002, 2010. https://doi.org/10.1103/PhysRevLett.105.067002
  63. T. Qian et al, "Absence of holelike Fermi surface in superconducting $K_{0.8}Fe_{1.7}Se_2$ revealed by ARPES," Phys. Rev. Lett., vol. 106, pp. 187001, 2011. https://doi.org/10.1103/PhysRevLett.106.187001
  64. Y. Zhang et al, "Nodeless superconducting gap in $A_xFe_2Se_2$(A=K, Cs) revealed angle-resolved photoemission spectroscopy," Nat. Mater., vol. 10, pp. 2981, 2011.
  65. Y. Zhang et al, "Heavily electron-doped electronic structure and isotropic superconducting gap in $A_xFe_2Se_2$ (A=K, Cs)," Nat. Mater., vol. 10, pp. 273, 2011. https://doi.org/10.1038/nmat2981
  66. D. Mou et al, "Distinct Fermi surface topology and nodelss superconducting gap in a $(Tl_{0.58}Rb_{0.42})Fe_{1.72}Se_2$ superconductor," Phys. Rev. Lett., vol. 106, pp. 107001, 2011. https://doi.org/10.1103/PhysRevLett.106.107001
  67. H. Miao et al, "Coexistence of orbital degeneracy lifting and superconductivity in iron-based superconductors," Phys. Rev. B, vol. 89, pp. 220503, 2014. https://doi.org/10.1103/PhysRevB.89.220503
  68. S. V. Borisenko et al, "One-Sign Order Parameter in Iron Based Superconductor," Symmetry, vol. 4, pp. 251, 2012. https://doi.org/10.3390/sym4010251
  69. H. Miao et al, "Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in $FeTe_{0.55}Se_{0.45}$," Phys. Rev. B, vol. 85, pp. 094506, 2012. https://doi.org/10.1103/PhysRevB.85.094506
  70. N. Xu et al, "Angle-resolved photoemission observation of isotropic superconducting gaps in isovalent Ru-substituted $Ba(Fe_{0.75}Ru_{0.25})_2As_2$," Phys. Rev. B, vol. 87, pp. 094513, 2013. https://doi.org/10.1103/PhysRevB.87.094513
  71. H. Ding et al, "Observation of Fermi-surface-dependent nodeless superconducting gaps in $Ba_{0.6}K_{0.4}Fe_2As_2$," Eur. Phys. Lett., vol. 83, pp. 47001, 2008. https://doi.org/10.1209/0295-5075/83/47001
  72. K. Terashima et al, "Fermi surface nesting induced strong pairing in iron-based superconductors," Proc. Natl. Acad. Sci., vol. 106, pp. 7330, 2009. https://doi.org/10.1073/pnas.0900469106
  73. Y. B. Huang et al, "Angle-resolved photoemission studies of the superconducting gap symmetry in Fe-based superconductors," Am. Ist. Phys. Adv., vol. 2, pp. 041409, 2012.
  74. T. Shimojima et al ,"Orbital Independent Superconducting Gaps in Iron Pnictides," Science, vol. 332, pp.564, 2011. https://doi.org/10.1126/science.1202150
  75. K. Umezawa et al, "Unconventional Anisotropic s-Wave Superconducting Gaps of the LiFeAs Iron-Pnictide Superconductor," Phys. Rev. Lett., vol. 108, pp. 037002, 2012. https://doi.org/10.1103/PhysRevLett.108.037002
  76. T. Kondo et al, "Momentum Dependence of the Superconducting Gap in $NdFeAsO_{0.9}F_{0.1}$ Single Crystals Measured by Angle Resolved Photoemission Spectroscopy," Phys. Rev. Lett., vol. 101, pp. 147003, 2008. https://doi.org/10.1103/PhysRevLett.101.147003
  77. K. Okazaki et al, "Octet-Line Node Structure of Superconducting Order Parameter in $KFe_2As_2$," Science, vol. 337, pp. 1314, 2012. https://doi.org/10.1126/science.1222793
  78. Y. Zhang et al, "Nodal superconducting-gap structure in ferropnictide superconductor $BaFe_2(As_{0.7}P_{0.3})_2$," Nat. Phys., vol. 8, pp. 2248, 2012.
  79. S. O. Diallo et al, "Itinerant magnetic excitations in antiferromagnetic $CaFe_2As_2$," Phys. Rev. Lett., vol. 102, pp. 187206, 2009. https://doi.org/10.1103/PhysRevLett.102.187206
  80. R. A. Ewings et al, "Itinerant spin excitations in $SrFe_2As_2$ measured by inelastic neutron scattering," Phys. Rev. B, vol. 83, pp. 214519, 2011. https://doi.org/10.1103/PhysRevB.83.214519
  81. J. Zho et al. "Spin waves and magnetic exchange interaction in $CaFe_2As_2$," Nat. Phys., vol. 5, pp. 555, 2011.
  82. L. W Harriger et al, "Nematic spin fluid in the tetragonal phase of $BaFe_2As_2$," Phys. Rev. B, vol. 84, pp. 054544, 2011. https://doi.org/10.1103/PhysRevB.84.054544
  83. H. Chen et al, "Coexistence of the spin-density wave and superconductivity in $Ba_{1-x}K_xFe_2As_2$," Euro. Phys. Lett., vol. 85, pp. 17006, 2009. https://doi.org/10.1209/0295-5075/85/17006
  84. D. K. Pratt et al, "Coexistence of competing Antiferromagnetic and Superconducting Phases in the Underdoped $Ba(Fe_{0.953}Co_{0.047})_2As_2$ Compound Using X-ray and Neutron Scattering Techniques," Phys. Rev. Lett., vol. 103, pp. 087001, 2009. https://doi.org/10.1103/PhysRevLett.103.087001
  85. S. Kasahara et al, "Evolution from non-Fermi to Fermi-liquid transport via isovalent doping in $BaFe_2(As_{1-x}P_x)_2$ superconductors," Phys. Rev. B, vol. 82, pp. 184519, 2010. https://doi.org/10.1103/PhysRevB.82.184519
  86. Z. R. Ye et al, "Doping dependence of the electronic structure in phosphorus-doped ferropnictide superconductor $BaFe_2(As_{1-x}P_x)_2$ studied by angle-resolved photoemission spectroscopy," Phys. Rev. B, vol. 86, pp. 035136, 2012. https://doi.org/10.1103/PhysRevB.86.035136
  87. M. J. Eom et al, "Evolution of transport properties of $BaFe_{2-x}Ru_xAs_2$ in a wide range of isovalent Ru substitution," Phys. Rev. B, vol. 85, pp. 024536, 2012. https://doi.org/10.1103/PhysRevB.85.024536
  88. K. Kirshenbaum et al, "Universal pair-breaking in transition-metal-substituted iron-pnictide superconductors," Phys. Rev. B, vol. 86, pp. 14505, 2012. https://doi.org/10.1103/PhysRevB.86.014505
  89. A. S. Sefat et al, "Superconductivity at 22K in Co-Doped $BaFe_2As_2$ Crystals," Phys. Rev. Lett., vol. 101, pp. 117004, 2008. https://doi.org/10.1103/PhysRevLett.101.117004
  90. H.-Y. Liu et al, "Pseudogap and Superconducting Gap in $SmFeAs(O_{1-x}F_x)$ Superconductor from Photoemission Spectroscopy," Chin. Phys. Lett., vol. 25, pp. 3761, 2008. https://doi.org/10.1088/0256-307X/25/10/066
  91. T. Sato et al, "Superconducting Gap and Pseudogap in Iron-Based Layered Superconductor $La(O_{1-x}F_x)FeAs$," J. Phys. Soc. Jpn., vol. 77, pp. 063708, 2008. https://doi.org/10.1143/JPSJ.77.063708
  92. H. Ikeda et al., "Pseudogap and Superconductivity in Iron-Based Layered Superconductor Studied by Flucutation-Exchange Approximation," J. Phys. Soc. Jpn., vol. 77, pp. 123707, 2008. https://doi.org/10.1143/JPSJ.77.123707
  93. T. Shimojima et al, "Pseudogap formation above the superconducting dome in iron pnictides," Phys. Rev. B, vol. 89, pp. 045101, 2014. https://doi.org/10.1103/PhysRevB.89.045101
  94. Y. Ishida et al, "Unusual Pseudogap Features Observed in Iron Oxypnictide Superconductors," J. Phys. Soc. Jpn., vol. 77, pp. 61, 2008.
  95. K. Ahilan et al, "$F^{19}$ NMR investigation of the iron pnictide superconductor $LaFeAsO_{0.89}F_{0.11}$," Phys. Rev. B, vol. 78, pp. 100501, 2008. https://doi.org/10.1103/PhysRevB.78.100501
  96. D. R. Garcia et al, "Core-level and valence-band study using angle-integrated photoemission on $LaFeAsO_{0.9}F_{0.1}$," Phys. Rev. B, vol. 78, pp. 245119, 2008. https://doi.org/10.1103/PhysRevB.78.245119
  97. T. Mertelj et al, "Distinct Pseudogap and Quasiparticle Relaxation Dynamics in the Superconducting State of Nearly Optimally Doped $SmFeAsO_{0.8}F_{0.2}$ Single Crystals," Phys. Rev. Lett., vol. 102, pp. 117002, 2009. https://doi.org/10.1103/PhysRevLett.102.117002
  98. M. A. Tanatar et al, "Pseudogap and its critical point in the heavily doped $Ba(Fe_{1-x}Co_x)_2As_2$ from c-axis resistivity measurements," Phys. Rev. B, vol. 82, pp. 134528, 2010. https://doi.org/10.1103/PhysRevB.82.134528
  99. S. H. Baek et al, "Pseudogap-like phase in $Ca(Fe_{1-x}Co_x)_2As_2$ revealed by 75As NQR," Phys. Rev. B, vol. 84, pp. 094510, 2011. https://doi.org/10.1103/PhysRevB.84.094510
  100. Y. C. Wen et al, "Gap Opening and Orbital Modification of Superconducting FeSe above the Structural Distortion," Phys. Rev. Lett., vol. 108, pp. 267002, 2012. https://doi.org/10.1103/PhysRevLett.108.267002
  101. S. J. Moon et al, "Infrared Measurement of the Pseudogap of P-Doped and Co-doped High-Temperature $BaFe_2As_2$ Superconductors," Phys. Rev. Lett., vol. 109, pp. 027006, 2012. https://doi.org/10.1103/PhysRevLett.109.027006
  102. K. Hashimoto et al, "A sharp peak of the zero-temperature penetration depth at optimal composition in $BaFe_2(As_{1-x}P_x)_2$," Science, vol. 336, pp. 1554, 2012. https://doi.org/10.1126/science.1219821
  103. P. Walmsley et al, "Quasiparticle mass enhancement close to the quantum critical point in $BaFe_2(As_{1-x}P_x)_2$," arXiv:1303.3396 https://doi.org/10.1103/PhysRevLett.110.257002
  104. J. K. Dong et al, "Quantum criticality and nodal superconductivity in the FeAs-based superconductor $KFe_2As_2$," Phys. Rev. Lett., vol. 104, pp. 087005, 2010. https://doi.org/10.1103/PhysRevLett.104.087005
  105. J. Dai et al, "Iron pnictides as a new setting for quantum criticality," Proc. Natl. Acad. Sci., vol. 106, pp. 4118, 2009. https://doi.org/10.1073/pnas.0900886106
  106. Y. Nakai et al, "Unconventional superconductivity and antiferro magnetic quantum critical behavior in the isovalent doped $BaFe_2(As_{1-x}P_x)_2$," Phys. Rev. Lett., vol. 105, pp. 107003, 2010. https://doi.org/10.1103/PhysRevLett.105.107003
  107. F. Zheng et al, "Antiferromagnetic FeSe monolayer on $SrTiO_3$: The charge doping and electric field effects," Scientific Reports, vol. 3, pp. 2213, 2013. https://doi.org/10.1038/srep02213
  108. Q.-Y. Wang et al, "Interface-induced High-Temperature Superconductivity in Single Unit-Cell FeSe Films on $SrTiO_3$," Chin. Phys. Lett., vol. 29, pp. 037402, 2012. https://doi.org/10.1088/0256-307X/29/3/037402
  109. S.-L He et al, "Phase diagram and high temperature superconductivity at 65K in tuning carrier concentration of single-layer FeSe films," Nat. Mater., vol. 12, pp. 605, 2013. https://doi.org/10.1038/nmat3648
  110. S. Y. Tan. et al, "Interface-induced superconductivity and strain-dependent spin density wave in FeSe/$SrTiO_3$ thin films," Nat. Mater., vol. 12, pp. 634, 2013. https://doi.org/10.1038/nmat3654
  111. Y. Y. Xiang et al, "High-temperature superconductivity at the FeSe/$SrTiO_3$ interface," Phys. Rev. B, vol. 86, pp. 134508, 2012. https://doi.org/10.1103/PhysRevB.86.134508

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