FeSe基超导体的拉曼散射研究
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摘要
拉曼散射是现代凝聚态物理研究的基础实验手段之一,利用其技术上的特色,可以探测凝聚态物质的各类激发及其耦合.FeSe基超导体具有块材、单层、缺位相、插层结构等不同的结构形态、丰富的电子和磁相图、从几K到40 K以上的易调节超导转变温度,因此形成了研究超导性质的一个理想平台,近些年引发了超导领域很多研究者的研究兴趣.本文首先对FeSe基超导体的结构、磁性和电子结构进行介绍,着重阐述了拉曼散射测量在FeSe基超导体研究中取得的研究进展.在声子拉曼响应方面,主要介绍FeSe基超导体的结构与其超导电性之间的关系;在磁的拉曼响应方面,分别对FeSe基材料的双磁子、自旋声子耦合等研究结果进行讨论;在电子拉曼响应方面,主要针对FeSe基超导体中的向列相问题进行了相关分析;最后对单层FeSe超导体和相关的拉曼测量做简要介绍.
Raman scattering is one of the fundamental techniques in modern condensed matter physics. Its technical uniqueness allows to probe a variety of excitations in condensed matter and their couplings. FeSe-based superconductors have abundant structural phases like bulk, monolayer, Fe-deficient phases, and intercalated phases. Meanwhile, they exhibit rich electronic and magnetic phase diagrams and easily tunable superconducting transition temperatures ranged from a few Kelvins up to more than 40 K. This leads to the formation of an ideal research platform for superconductivity and has attracted a great deal of interest in the field. In this paper, we made a brief introduction to the structural phases,magnetism and electronic structures of FeSe-based superconductors. And we focused on the recent progress on Raman scattering studies of FeSe-based superconductors. For phononic Raman scattering, we introduced the Raman scattering measurement of the phonons in the Fe(Se,Te) system firstly. Next, in order to further explore the influence of doping on Tc, we discussed the doping/substitution of A-sites and Fe-sites of A_xFe_(2-y)Se_2. Finally, we studied the correlation between superconductivity and various structures. We then discussed two-magnon and spin-phonon coupling in the materials. We discussed the relationship between magnetic order and superconductivity, and the effect of magnetic order on phonons.For electronic Raman response, we presented the discussions and analysis on electronic nematic phases. We introduced the observation of nematic phases by different measurement methods. And we discussed the origin of nematic phases:spin fluctuations or/and orbital(charge) fluctuations, different measurement methods have different conclusions. Finally,we introduced the studies in monolayer FeSe and some Raman scattering results there. We introduced the discovery of Tc above 77 K in monolayer FeSe/SrTiO_3. And we discussed many novel physical properties such as the opening of energy gap in 1 UC FeSe/NbSTO and the charge transfer and ferroelectric phase transition between 1-UC thin film and NbSTO substrate.
Raman scattering is one of the fundamental techniques in modern condensed matter physics. Its technical uniqueness allows to probe a variety of excitations in condensed matter and their couplings. FeSe-based superconductors have abundant structural phases like bulk, monolayer, Fe-deficient phases, and intercalated phases. Meanwhile, they exhibit rich electronic and magnetic phase diagrams and easily tunable superconducting transition temperatures ranged from a few Kelvins up to more than 40 K. This leads to the formation of an ideal research platform for superconductivity and has attracted a great deal of interest in the field. In this paper, we made a brief introduction to the structural phases,magnetism and electronic structures of FeSe-based superconductors. And we focused on the recent progress on Raman scattering studies of FeSe-based superconductors. For phononic Raman scattering, we introduced the Raman scattering measurement of the phonons in the Fe(Se,Te) system firstly. Next, in order to further explore the influence of doping on Tc, we discussed the doping/substitution of A-sites and Fe-sites of A_xFe_(2-y)Se_2. Finally, we studied the correlation between superconductivity and various structures. We then discussed two-magnon and spin-phonon coupling in the materials. We discussed the relationship between magnetic order and superconductivity, and the effect of magnetic order on phonons.For electronic Raman response, we presented the discussions and analysis on electronic nematic phases. We introduced the observation of nematic phases by different measurement methods. And we discussed the origin of nematic phases:spin fluctuations or/and orbital(charge) fluctuations, different measurement methods have different conclusions. Finally,we introduced the studies in monolayer FeSe and some Raman scattering results there. We introduced the discovery of Tc above 77 K in monolayer FeSe/SrTiO_3. And we discussed many novel physical properties such as the opening of energy gap in 1 UC FeSe/NbSTO and the charge transfer and ferroelectric phase transition between 1-UC thin film and NbSTO substrate.
引文
1 Kamihara Y,Watanabe T,Hirano M,et al.Iron-based layered superconductor La[O1-xFx]Fe As(x=0.05-0.12)with Tc=26 K.J Am Chem Soc,2008,130:3296-3297
2 Hsu F C,Luo J Y,Yeh K W,et al.Superconductivity in the Pb O-type structureα-FeSe.Proc Natl Acad Sci USA,2008,105:14262-14264[]
3 Wang X C,Liu Q Q,Lv Y X,et al.The superconductivity at 18 K in Li Fe As system.Solid State Commun,2008,148:538-540,ar Xiv:0806.4688
4 Rotter M,Tegel M,Johrendt D.Superconductivity at 38 K in the iron arsenide(Ba1-xKx)Fe2As2.Phys Rev Lett,2008,101:107006,ar Xiv:0805.4630
5 Chen G F,Li Z,Wu D,et al.Superconductivity at 41 K and Its competition with spin-density-wave instability in layered Ce O1-xFxFe As.Phys Rev Lett,2008,100:247002,ar Xiv:0803.3790
6 Zhu X,Han F,Mu G,et al.Transition of stoichiometric Sr2VO3Fe As to a superconducting state at 37.2 K.Phys Rev B,2009,79:220512,ar Xiv:0904.1732
7 Schuster W,Mikler H,Komarek K L.Transition metal-chalcogen systems.VII.The iron-selenium phase diagram.Monatshefte Chem,1979,110:1153-1170
8 Margadonna S,Takabayashi Y,Mc Donald M T,et al.Crystal structure of the new FeSe1-xsuperconductor.Chem Commun,2008,130:5607
9 Wu M K,Hsu F C,Yeh K W,et al.The development of the superconducting Pb O-typeβ-FeSe and related compounds.Phys C-Supercond,2009,469:340-349
10 Margadonna S,Takabayashi Y,Ohishi Y,et al.Pressure evolution of the low-temperature crystal structure and bonding of the superconductor FeSe(Tc=37 K).Phys Rev B,2009,80:064506,ar Xiv:0903.2204
11 Garbarino G,Sow A,Lejay P,et al.High-temperature superconductivity(Tconset at 34 K)in the high-pressure orthorhombic phase of FeSe.Europhys Lett,2009,86:27001,ar Xiv:0903.3888
12 Bao W,Huang Q Z,Chen G F,et al.A novel large moment antiferromagnetic order in K0.8Fe1.6Se2superconductor.Chin Phys Lett,2011,28:086104,ar Xiv:1102.0830
13 Niu X H,Peng R,Xu H C,et al.Surface electronic structure and isotropic superconducting gap in(Li0.8Fe0.2)OHFeSe.Phys Rev B,2015,92:060504,ar Xiv:1506.02825
14 Ye F,Chi S,Bao W,et al.Common crystalline and magnetic structure of superconducting A2Fe4Se5(A=K,Rb,Cs,Tl)single crystals measured using neutron diffraction.Phys Rev Lett,2011,107:137003
15 Watson M D,Kim T K,Rhodes L C,et al.Evidence for unidirectional nematic bond ordering in FeSe.Phys Rev B,2016,94:201107,ar Xiv:1603.04545
16 Mou D,Liu S,Jia X,et al.Distinct Fermi surface topology and nodeless superconducting gap in a(Tl0.58Rb0.42)Fe1.72Se2superconductor.Phys Rev Lett,2011,106:107001,ar Xiv:1101.4556
17 Zhao L,Liang A,Yuan D,et al.Common electronic origin of superconductivity in(Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/Sr Ti O3films.Nat Commun,2016,7:10608,ar Xiv:1505.06361
18 Liu D,Zhang W,Mou D,et al.Electronic origin of high-temperature superconductivity in single-layer FeSe superconductor.Nat Commun,2012,3:931,ar Xiv:1202.5849
19 Lei B,Cui J H,Xiang Z J,et al.Evolution of high-temperature superconductivity from a low-Tcphase tuned by carrier concentration in FeSe thin flakes.Phys Rev Lett,2016,116:077002,ar Xiv:1509.00620
20 Sun L,Chen X J,Guo J,et al.Re-emerging superconductivity at 48 kelvin in iron chalcogenides.Nature,2012,483:67-69,ar Xiv:1110.2600
21 Sun J P,Matsuura K,Ye G Z,et al.Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe.Nat Commun,2016,7:12146,ar Xiv:1512.06951
22 Devereaux T P,Hackl R.Inelastic light scattering from correlated electrons.Rev Mod Phys,2007,79:175-233
23 Paglione J,Greene R L.High-temperature superconductivity in iron-based materials.Nat Phys,2010,6:645-658,ar Xiv:1006.4618
24 Mizuguchi Y,Tomioka F,Tsuda S,et al.Superconductivity at 27 K in tetragonal FeSe under high pressure.Appl Phys Lett,2008,93:152505,ar Xiv:0807.4315
25 Medvedev S,Mc Queen T M,Troyan I A,et al.Electronic and magnetic phase diagram ofβ-Fe1.01Se with superconductivity at 36.7 K under pressure.Nat Mater,2009,8:630-633,ar Xiv:0903.2143
26 Masaki S,Kotegawa H,Hara Y,et al.Precise pressure dependence of the superconducting transition temperature of FeSe:Resistivity and77SeNMR study.J Phys Soc Jpn,2009,78:063704,ar Xiv:0903.2594
27 Xia T L,Hou D,Zhao S C,et al.Raman phonons ofα-Fe Te and Fe1.03Se0.3Te0.7single crystals.Phys Rev B,2009,79:140510,ar Xiv:0811.2350
28 Okazaki K,Sugai S,Niitaka S,et al.Phonon,two-magnon,and electronic Raman scattering of Fe1+yTe1-xSex.Phys Rev B,2011,83:035103,ar Xiv:1010.2374
29 Kumar P,Kumar A,Saha S,et al.Anomalous Raman scattering from phonons and electrons of superconducting.Solid State Commun,2010,150:557-560,ar Xiv:1004.1612
30 Qin Z,Zhang C,O’Malley S,et al.Crystal field excitations in the Raman spectra of.Solid State Commun,2010,150:768-771
31 Gnezdilov V,Pashkevich Y,Lemmens P,et al.Anomalous optical phonons in Fe Te chalcogenides:Spin state,magnetic order,and lattice anharmonicity.Phys Rev B,2011,83:245127,ar Xiv:1102.3688
32 Um Y J,Subedi A,Toulemonde P,et al.Anomalous dependence of c-axis polarized Fe B1gphonon mode with Fe and Se concentrations in Fe1+yTe1-xSex.Phys Rev B,2012,85:064519,ar Xiv:1202.0375
33 Gnezdilov V,Pashkevich Y G,Lemmens P,et al.Interplay between lattice and spin states degree of freedom in the FeSe superconductor:Dynamic spin state instabilities.Phys Rev B,2013,87:144508,ar Xiv:1301.1960
34 Popovi?Z V,Lazarevi?N,Bogdanovi?S,et al.Signatures of the spin-phonon coupling in Fe1+yTe1-xSexalloys.Solid State Commun,2014,193:51-55
35 Zhang A M,Liu K,Xiao J H,et al.Vacancy ordering and phonon spectrum of the iron-based superconductor K0.8Fe1.6Se2.Phys Rev B,2012,85:024518,ar Xiv:1101.2168
36 Litvinchuk A P,Hadjiev V G,Iliev M N,et al.Raman-scattering study of KxSr1-xFe2As2(x=0.0,0.4).Phys Rev B,2008,78:060503,ar Xiv:0807.2284
37 Tiedje O,Krasovskii E E,Schattke W,et al.Bridging from Th Cr2Si2-type materials to hexagonal dichalcogenides:An ab initio and experimental study of KCu2Se2.Phys Rev B,2003,67:134105
38 Zhang A M,Liu K,He J B,et al.Effect of iron content and potassium substitution in A0.8Fe1.6Se2(A=K,Rb,Tl)superconductors:A Raman scattering investigation.Phys Rev B,2012,86:134502,ar Xiv:1105.1198
39 Zhang A M,Xia T L,Liu K,et al.Superconductivity at 44 K in K intercalated FeSe system with excess Fe.Sci Rep,2013,3:1216,ar Xiv:1203.1533
40 Guo J,Jin S,Wang G,et al.Superconductivity in the iron selenide KxFe2Se2(0≤x≤1.0).Phys Rev B,2010,82:180520,ar Xiv:1012.2924
41 Wang D M,He J B,Xia T L,et al.Effect of varying iron content on the transport properties of the potassium-intercalated iron selenide KxFe2-ySe2.Phys Rev B,2011,83:132502,ar Xiv:1101.0789
42 Luo X G,Wang X F,Ying J J,et al.Crystal structure,physical properties and superconductivity in AxFe2Se2single crystals.New J Phys,2011,13:053011,ar Xiv:1101.5670
43 Ying T P,Chen X L,Wang G,et al.Observation of superconductivity at 30-46 K in AxFe2Se2(A=Li,Na,Ba,Sr,Ca,Yb and Eu).Sci Rep,2012,2:426,ar Xiv:1202.4340
44 Mizuguchi Y,Hara Y,Deguchi K,et al.Anion height dependence of Tcfor the Fe-based superconductor.Supercond Sci Technol,2010,23:054013,ar Xiv:1001.1801
45 Lu X F,Wang N Z,Zhang G H,et al.Superconductivity in Li Fe O2Fe2Se2with anti-Pb O-type spacer layers.Phys Rev B,2014,89:020507,ar Xiv:1309.3833
46 Lu X F,Wang N Z,Luo X G,et al.Superconductivity and phase diagram of(Li0.8Fe0.2)OHFeSe1-xSx.Phys Rev B,2014,90:214520,ar Xiv:1501.01157
47 Sugai S,Mizuno Y,Kiho K,et al.Pairing symmetry of the multiorbital pnictide superconductor Ba Fe1.84Co0.16As2from Raman scattering.Phys Rev B,2010,82:140504
48 Sugai S,Mizuno Y,Watanabe R,et al.Spin-density-wave gap with Dirac nodes and two-magnon Raman scattering in Ba Fe2As2.J Phys Soc Jpn,2012,81:024718,ar Xiv:1201.5207[]
49 Han M J,Yin Q,Pickett W E,et al.Anisotropy,itineracy,and magnetic frustration in high-Tciron pnictides.Phys Rev Lett,2009,102:107003,ar Xiv:0811.0034
50 Han M J,Savrasov S Y.Doping driven(π,0)nesting and magnetic properties of Fe1+xTe superconductors.Phys Rev Lett,2009,103:067001
51 Zhao J,Adroja D T,Yao D X,et al.Spin waves and magnetic exchange interactions in Ca Fe2As2.Nat Phys,2009,5:555-560,ar Xiv:0903.2686
52 Sugai S,Suzuki H,Takayanagi Y,et al.Carrier-density-dependent momentum shift of the coherent peak and the LO phonon mode in p-type high-Tcsuperconductors.Phys Rev B,2003,68:184504
53 Zhang A M,Xiao J H,Li Y S,et al.Two-magnon Raman scattering in A0.8Fe1.6Se2systems(A=K,Rb,Cs,and Tl):Competition between superconductivity and antiferromagnetic order.Phys Rev B,2012,85:214508,ar Xiv:1106.2706
54 Yan X W,Gao M,Lu Z Y,et al.Ternary iron selenide K0.8Fe1.6Se2is an antiferromagnetic semiconductor.Phys Rev B,2011,83:233205,ar Xiv:1102.2215
55 Lei B,Xiang Z J,Lu X F,et al.Gate-tuned superconductor-insulator transition in(Li,Fe)OHFeSe.Phys Rev B,2016,93:060501,ar Xiv:1503.02457
56 Jovanovi?V P,Fruchter L,Li Z Z,et al.Anisotropy of the in-plane angular magnetoresistance of electron-doped Sr1-xLaxCu O2thin films.Phys Rev B,2010,81:134520,ar Xiv:1004.4163
57 Fang M H,Pham H M,Qian B,et al.Superconductivity close to magnetic instability in Fe(Se1-xTex)0.82.Phys Rev B,2008,78:224503,ar Xiv:0807.4775
58 Yeh K W,Huang T W,Huang Y,et al.Tellurium substitution effect on superconductivity of theα-phase iron selenide.Europhys Lett,2008,84:37002,ar Xiv:0808.0474
59 Martinelli A,Palenzona A,Tropeano M,et al.From antiferromagnetism to superconductivity in Fe1+yTe1-xSex(0≤x≤0.20):Neutron powder diffraction analysis.Phys Rev B,2010,81:094115,ar Xiv:1002.3517
60 Bao W,Qiu Y,Huang Q,et al.Tunable(δπ,δπ)-type antiferromagnetic order inα-Fe(Te,Se)superconductors.Phys Rev Lett,2009,102:247001
61 Li S,de La Cruz C,Huang Q,et al.First-order magnetic and structural phase transitions in Fe1+ySexTe1-x.Phys Rev B,2009,79:054503,ar Xiv:0811.0195
62 Ksenofontov V,Wortmann G,Chumakov A I,et al.Density of phonon states in superconducting FeSe as a function of temperature and pressure.Phys Rev B,2010,81:184510,ar Xiv:1004.2007
63 Mc Queen T M,Huang Q,Ksenofontov V,et al.Extreme sensitivity of superconductivity to stoichiometry in Fe1+δSe.Phys Rev B,2009,79:014522,ar Xiv:0811.1613
64 Phelan D,Millican J N,Thomas E L,et al.Neutron scattering measurements of the phonon density of states of FeSe1-xsuperconductors.Phys Rev B,2009,79:014519,ar Xiv:0811.1215
65 Homes C C,Dai Y M,Schneeloch J,et al.Phonon anomalies in some iron telluride materials.Phys Rev B,2016,93:125135,ar Xiv:1602.08077
66 Xu B,Dai Y M,Shen B,et al.Anomalous phonon redshift in K-doped Ba Fe2As2iron pnictides.Phys Rev B,2015,91:104510,ar Xiv:1503.03838
67 Zhang Y,Chen F,He C,et al.Strong correlations and spin-density-wave phase induced by a massive spectral weight redistribution inα-Fe1.06Te.Phys Rev B,2010,82:165113
68 Lin P H,Texier Y,Taleb-Ibrahimi A,et al.Nature of the bad metallic behavior of Fe1.06Te inferred from its evolution in the magnetic state.Phys Rev Lett,2013,111:217002,ar Xiv:1306.2603
69 Stewart G R.Superconductivity in iron compounds.Rev Mod Phys,2011,83:1589-1652,ar Xiv:1106.1618
70 Fernandes R M,Chubukov A V,Schmalian J.What drives nematic order in iron-based superconductors?Nat Phys,2014,10:97-104
71 Chu J H,Analytis J G,De Greve K,et al.In-plane resistivity anisotropy in an underdoped iron arsenide superconductor.Science,2010,329:824-826
72 Tanatar M A,Blomberg E C,Kreyssig A,et al.Uniaxial-strain mechanical detwinning of Ca Fe2As2and Ba Fe2As2crystals:Optical and transport study.Phys Rev B,2010,81:184508,ar Xiv:1002.3801
73 Knolle J,Eremin I,Akbari A,et al.Nematic electronic structure in the“parent”state of the iron-based superconductor Ca(Fe1-xCox)2As2.Science,2010,327:181-184
74 Yi M,Lu D,Chu J H,et al.Symmetry-breaking orbital anisotropy observed for detwinned Ba(Fe1-xCox)2As2above the spin density wave transition.Proc Natl Acad Sci USA,2011,108:6878-6883,ar Xiv:1011.0050
75 Kasahara S,Shi H J,Hashimoto K,et al.Electronic nematicity above the structural and superconducting transition in Ba Fe2(As1-xPx)2.Nature,2012,486:382-385
76 Shimojima T,Sonobe T,Malaeb W,et al.Pseudogap formation above the superconducting dome in iron pnictides.Phys Rev B,2014,89:045101,ar Xiv:1305.3875
77 Zhang Y,He C,Ye Z R,et al.Symmetry breaking via orbital-dependent reconstruction of electronic structure in detwinned Na Fe As.Phys Rev B,2012,85:085121,ar Xiv:1111.6430
78 Yi M,Lu D H,Moore R G,et al.Electronic reconstruction through the structural and magnetic transitions in detwinned Na Fe As.New J Phys,2012,14:073019,ar Xiv:1111.6134
79 Rosenthal E P,Andrade E F,Arguello C J,et al.Visualization of electron nematicity and unidirectional antiferroic fluctuations at high temperatures in Na Fe As.Nat Phys,2014,10:225-232,ar Xiv:1307.3526
80 Nakayama K,Miyata Y,Phan G N,et al.Reconstruction of band structure induced by electronic nematicity in an FeSe superconductor.Phys Rev Lett,2014,113:237001,ar Xiv:1404.0857
81 Watson M D,Kim T K,Haghighirad A A,et al.Emergence of the nematic electronic state in FeSe.Phys Rev B,2015,91:155106,ar Xiv:1502.02917
82 Zhang P,Qian T,Richard P,et al.Observation of two distinct dxz/dyzband splittings in FeSe.Phys Rev B,2015,91:214503
83 Fedorov A,Yaresko A,Kim T K,et al.Effect of nematic ordering on electronic structure of FeSe.Sci Rep,2016,6:36834,ar Xiv:1606.03022
84 Huynh K K,Tanabe Y,Urata T,et al.Electric transport of a single-crystal iron chalcogenide FeSe superconductor:Evidence of symmetrybreakdown nematicity and additional ultrafast Dirac cone-like carriers.Phys Rev B,2014,90:144516,ar Xiv:1405.3815
85 Mc Queen T M,Williams A J,Stephens P W,et al.Tetragonal-to-orthorhombic structural phase transition at 90 K in the superconductor Fe1.01Se.Phys Rev Lett,2009,103:057002,ar Xiv:0905.1065
86 B?hmer A E,Arai T,Hardy F,et al.Origin of the tetragonal-to-orthorhombic phase transition in FeSe:A combined thermodynamic and NMRstudy of nematicity.Phys Rev Lett,2015,114:027001,ar Xiv:1407.5497
87 B?hmer A E,Hardy F,Eilers F,et al.Lack of coupling between superconductivity and orthorhombic distortion in stoichiometric singlecrystalline FeSe.Phys Rev B,2013,87:180505,ar Xiv:1303.2026
88 Wang Q,Shen Y,Pan B,et al.Strong interplay between stripe spin fluctuations,nematicity and superconductivity in FeSe.Nat Mater,2016,15:159-163,ar Xiv:1502.07544
89 Shamoto S,Matsuoka K,Kajimoto R,et al.Spin nematic susceptibility studied by inelastic neutron scattering in FeSe,ar Xiv:1511.04267
90 Baek S H,Efremov D V,Ok J M,et al.Orbital-driven nematicity in FeSe.Nat Mater,2015,14:210-214,ar Xiv:1408.1875
91 Wang F,Kivelson S A,Lee D H.Nematicity and quantum paramagnetism in FeSe.Nat Phys,2015,11:959-963,ar Xiv:1501.00844
92 Glasbrenner J K,Mazin I I,Jeschke H O,et al.Effect of magnetic frustration on nematicity and superconductivity in iron chalcogenides.Nat Phys,2015,11:953-958,ar Xiv:1501.04946
93 Yu R,Si Q.Antiferroquadrupolar and ising-nematic orders of a frustrated bilinear-biquadratic heisenberg model and implications for the magnetism of FeSe.Phys Rev Lett,2015,115:116401,ar Xiv:1501.05926
94 Luo C W,Chung C P,Wang S H,et al.Unveiling the hidden nematicity and spin subsystem in FeSe.npj Quant Mater,2017,2:32,ar Xiv:1603.08710
95 Massat P,Farina D,Paul I,et al.Charge-induced nematicity in FeSe.Proc Natl Acad Sci USA,2016,113:9177-9181,ar Xiv:1603.01492
96 Locquet J P,Perret J,Fompeyrine J,et al.Doubling the critical temperature of La1.9Sr0.1Cu O4using epitaxial strain.Nature,1998,394:453-456
97 Strongin M,Kammerer O F,Crow J E,et al.Enhanced superconductivity in layered metallic films.Phys Rev Lett,1968,21:1320-1323
98 Wang Q Y,Li Z,Zhang W H,et al.Interface-induced high-temperature superconductivity in single unit-cell FeSe films on Sr Ti O3.Chin Phys Lett,2012,29:037402,ar Xiv:1201.5694
99 Ge J F,Liu Z L,Liu C,et al.Superconductivity above 100 K in single-layer FeSe films on doped Sr Ti O3.Nat Mater,2015,14:285-289,ar Xiv:1406.3435
100 Zhang W,Li Z,Li F,et al.Interface charge doping effects on superconductivity of single-unit-cell FeSe films on Sr Ti O3substrates.Phys Rev B,2014,89:060506
101 Lee J J,Schmitt F T,Moore R G,et al.Interfacial mode coupling as the origin of the enhancement of Tcin FeSe films on Sr Ti O3.Nature,2014,515:245-248,ar Xiv:1312.2633
102 Peng R,Xu H C,Tan S Y,et al.Tuning the band structure and superconductivity in single-layer FeSe by interface engineering.Nat Commun,2014,5:5044
103 Peng R,Shen X P,Xie X,et al.Measurement of an enhanced superconducting phase and a pronounced anisotropy of the energy gap of a strained FeSe single layer in FeSe/Nb:Sr Ti O3/KTa O3heterostructures using photoemission spectroscopy.Phys Rev Lett,2014,112:107001
104 Zhang W H,Sun Y,Zhang J S,et al.Direct observation of high-temperature superconductivity in one-unit-cell FeSe films.Chin Phys Lett,2014,31:017401,ar Xiv:1311.5370
105 Zhang Z,Wang Y H,Song Q,et al.Onset of the Meissner effect at 65 K in FeSe thin film grown on Nb-doped Sr Ti O3substrate.Sci Bull,2015,60:1301-1304
106 Deng L Z,Lv B,Wu Z,et al.Meissner and mesoscopic superconducting states in 1-4 unit-cell FeSe films.Phys Rev B,2014,90:214513,ar Xiv:1311.6459
107 Sun Y,Zhang W,Xing Y,et al.High temperature superconducting FeSe films on Sr Ti O3substrates.Sci Rep,2015,4:6040,ar Xiv:1404.3464
108 Cui Y T,Moore R G,Zhang A M,et al.Interface ferroelectric transition near the gap-opening temperature in a single-unit-cell FeSe film grown on Nb-Doped Sr Ti O3substrate.Phys Rev Lett,2015,114:037002
109 Fleury P A,Scott J F,Worlock J M.Soft phonon modes and the 110 K phase transition in Sr Ti O3.Phys Rev Lett,1968,21:16-19
110 Bianchi U,Kleemann W,Bednorz J G.Raman scattering of ferroelectric Sr1-xCaxTi O3,x=0.007.J Phys-Condens Matter,1994,6:1229-1238
111 Scott J F.Interpretation of phonon anomalies in Sr Ti O3near 37 K.Ferroelectrics Lett Sect,1995,20:89-95
112 Taniguchi H,Yagi T,Takesada M,et al.Isotope effect on the soft-mode dynamics of Sr Ti O3studied by Raman scattering.Phys Rev B,2005,72:064111
113 Taniguchi H,Itoh M,Yagi T.Ideal soft mode-type quantum phase transition and phase coexistence at quantum critical point in18O-exchanged Sr Ti O3.Phys Rev Lett,2007,99:017602
114 Zhong W,Vanderbilt D.Competing structural instabilities in cubic perovskites.Phys Rev Lett,1995,74:2587-2590
115 Müller K A,Burkard H.Sr Ti O3:An intrinsic quantum paraelectric below 4 K.Phys Rev B,1979,19:3593-3602
116 Rowley S E,Spalek L J,Smith R P,et al.Ferroelectric quantum criticality.Nat Phys,2014,10:367-372,ar Xiv:0903.1445
117 Fleury P A,Worlock J M.Electric-field-induced Raman scattering in Sr Ti O3and KTa O3.Phys Rev,1968,174:613-623
118 Itoh M,Wang R,Inaguma Y,et al.Ferroelectricity induced by oxygen isotope exchange in strontium titanate perovskite.Phys Rev Lett,1999,82:3540-3543
119 Nilsen W G,Skinner J G.Raman spectrum of strontium titanate.J Chem Phys,1968,48:2240-2248
120 Uwe H,Yamaguchi H,Sakudo T.Ferroelectric microregion in KTa1-xNbxO3and Sr Ti O3.Ferroelectrics,1989,96:123-126
2 Hsu F C,Luo J Y,Yeh K W,et al.Superconductivity in the Pb O-type structureα-FeSe.Proc Natl Acad Sci USA,2008,105:14262-14264[]
3 Wang X C,Liu Q Q,Lv Y X,et al.The superconductivity at 18 K in Li Fe As system.Solid State Commun,2008,148:538-540,ar Xiv:0806.4688
4 Rotter M,Tegel M,Johrendt D.Superconductivity at 38 K in the iron arsenide(Ba1-xKx)Fe2As2.Phys Rev Lett,2008,101:107006,ar Xiv:0805.4630
5 Chen G F,Li Z,Wu D,et al.Superconductivity at 41 K and Its competition with spin-density-wave instability in layered Ce O1-xFxFe As.Phys Rev Lett,2008,100:247002,ar Xiv:0803.3790
6 Zhu X,Han F,Mu G,et al.Transition of stoichiometric Sr2VO3Fe As to a superconducting state at 37.2 K.Phys Rev B,2009,79:220512,ar Xiv:0904.1732
7 Schuster W,Mikler H,Komarek K L.Transition metal-chalcogen systems.VII.The iron-selenium phase diagram.Monatshefte Chem,1979,110:1153-1170
8 Margadonna S,Takabayashi Y,Mc Donald M T,et al.Crystal structure of the new FeSe1-xsuperconductor.Chem Commun,2008,130:5607
9 Wu M K,Hsu F C,Yeh K W,et al.The development of the superconducting Pb O-typeβ-FeSe and related compounds.Phys C-Supercond,2009,469:340-349
10 Margadonna S,Takabayashi Y,Ohishi Y,et al.Pressure evolution of the low-temperature crystal structure and bonding of the superconductor FeSe(Tc=37 K).Phys Rev B,2009,80:064506,ar Xiv:0903.2204
11 Garbarino G,Sow A,Lejay P,et al.High-temperature superconductivity(Tconset at 34 K)in the high-pressure orthorhombic phase of FeSe.Europhys Lett,2009,86:27001,ar Xiv:0903.3888
12 Bao W,Huang Q Z,Chen G F,et al.A novel large moment antiferromagnetic order in K0.8Fe1.6Se2superconductor.Chin Phys Lett,2011,28:086104,ar Xiv:1102.0830
13 Niu X H,Peng R,Xu H C,et al.Surface electronic structure and isotropic superconducting gap in(Li0.8Fe0.2)OHFeSe.Phys Rev B,2015,92:060504,ar Xiv:1506.02825
14 Ye F,Chi S,Bao W,et al.Common crystalline and magnetic structure of superconducting A2Fe4Se5(A=K,Rb,Cs,Tl)single crystals measured using neutron diffraction.Phys Rev Lett,2011,107:137003
15 Watson M D,Kim T K,Rhodes L C,et al.Evidence for unidirectional nematic bond ordering in FeSe.Phys Rev B,2016,94:201107,ar Xiv:1603.04545
16 Mou D,Liu S,Jia X,et al.Distinct Fermi surface topology and nodeless superconducting gap in a(Tl0.58Rb0.42)Fe1.72Se2superconductor.Phys Rev Lett,2011,106:107001,ar Xiv:1101.4556
17 Zhao L,Liang A,Yuan D,et al.Common electronic origin of superconductivity in(Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/Sr Ti O3films.Nat Commun,2016,7:10608,ar Xiv:1505.06361
18 Liu D,Zhang W,Mou D,et al.Electronic origin of high-temperature superconductivity in single-layer FeSe superconductor.Nat Commun,2012,3:931,ar Xiv:1202.5849
19 Lei B,Cui J H,Xiang Z J,et al.Evolution of high-temperature superconductivity from a low-Tcphase tuned by carrier concentration in FeSe thin flakes.Phys Rev Lett,2016,116:077002,ar Xiv:1509.00620
20 Sun L,Chen X J,Guo J,et al.Re-emerging superconductivity at 48 kelvin in iron chalcogenides.Nature,2012,483:67-69,ar Xiv:1110.2600
21 Sun J P,Matsuura K,Ye G Z,et al.Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe.Nat Commun,2016,7:12146,ar Xiv:1512.06951
22 Devereaux T P,Hackl R.Inelastic light scattering from correlated electrons.Rev Mod Phys,2007,79:175-233
23 Paglione J,Greene R L.High-temperature superconductivity in iron-based materials.Nat Phys,2010,6:645-658,ar Xiv:1006.4618
24 Mizuguchi Y,Tomioka F,Tsuda S,et al.Superconductivity at 27 K in tetragonal FeSe under high pressure.Appl Phys Lett,2008,93:152505,ar Xiv:0807.4315
25 Medvedev S,Mc Queen T M,Troyan I A,et al.Electronic and magnetic phase diagram ofβ-Fe1.01Se with superconductivity at 36.7 K under pressure.Nat Mater,2009,8:630-633,ar Xiv:0903.2143
26 Masaki S,Kotegawa H,Hara Y,et al.Precise pressure dependence of the superconducting transition temperature of FeSe:Resistivity and77SeNMR study.J Phys Soc Jpn,2009,78:063704,ar Xiv:0903.2594
27 Xia T L,Hou D,Zhao S C,et al.Raman phonons ofα-Fe Te and Fe1.03Se0.3Te0.7single crystals.Phys Rev B,2009,79:140510,ar Xiv:0811.2350
28 Okazaki K,Sugai S,Niitaka S,et al.Phonon,two-magnon,and electronic Raman scattering of Fe1+yTe1-xSex.Phys Rev B,2011,83:035103,ar Xiv:1010.2374
29 Kumar P,Kumar A,Saha S,et al.Anomalous Raman scattering from phonons and electrons of superconducting.Solid State Commun,2010,150:557-560,ar Xiv:1004.1612
30 Qin Z,Zhang C,O’Malley S,et al.Crystal field excitations in the Raman spectra of.Solid State Commun,2010,150:768-771
31 Gnezdilov V,Pashkevich Y,Lemmens P,et al.Anomalous optical phonons in Fe Te chalcogenides:Spin state,magnetic order,and lattice anharmonicity.Phys Rev B,2011,83:245127,ar Xiv:1102.3688
32 Um Y J,Subedi A,Toulemonde P,et al.Anomalous dependence of c-axis polarized Fe B1gphonon mode with Fe and Se concentrations in Fe1+yTe1-xSex.Phys Rev B,2012,85:064519,ar Xiv:1202.0375
33 Gnezdilov V,Pashkevich Y G,Lemmens P,et al.Interplay between lattice and spin states degree of freedom in the FeSe superconductor:Dynamic spin state instabilities.Phys Rev B,2013,87:144508,ar Xiv:1301.1960
34 Popovi?Z V,Lazarevi?N,Bogdanovi?S,et al.Signatures of the spin-phonon coupling in Fe1+yTe1-xSexalloys.Solid State Commun,2014,193:51-55
35 Zhang A M,Liu K,Xiao J H,et al.Vacancy ordering and phonon spectrum of the iron-based superconductor K0.8Fe1.6Se2.Phys Rev B,2012,85:024518,ar Xiv:1101.2168
36 Litvinchuk A P,Hadjiev V G,Iliev M N,et al.Raman-scattering study of KxSr1-xFe2As2(x=0.0,0.4).Phys Rev B,2008,78:060503,ar Xiv:0807.2284
37 Tiedje O,Krasovskii E E,Schattke W,et al.Bridging from Th Cr2Si2-type materials to hexagonal dichalcogenides:An ab initio and experimental study of KCu2Se2.Phys Rev B,2003,67:134105
38 Zhang A M,Liu K,He J B,et al.Effect of iron content and potassium substitution in A0.8Fe1.6Se2(A=K,Rb,Tl)superconductors:A Raman scattering investigation.Phys Rev B,2012,86:134502,ar Xiv:1105.1198
39 Zhang A M,Xia T L,Liu K,et al.Superconductivity at 44 K in K intercalated FeSe system with excess Fe.Sci Rep,2013,3:1216,ar Xiv:1203.1533
40 Guo J,Jin S,Wang G,et al.Superconductivity in the iron selenide KxFe2Se2(0≤x≤1.0).Phys Rev B,2010,82:180520,ar Xiv:1012.2924
41 Wang D M,He J B,Xia T L,et al.Effect of varying iron content on the transport properties of the potassium-intercalated iron selenide KxFe2-ySe2.Phys Rev B,2011,83:132502,ar Xiv:1101.0789
42 Luo X G,Wang X F,Ying J J,et al.Crystal structure,physical properties and superconductivity in AxFe2Se2single crystals.New J Phys,2011,13:053011,ar Xiv:1101.5670
43 Ying T P,Chen X L,Wang G,et al.Observation of superconductivity at 30-46 K in AxFe2Se2(A=Li,Na,Ba,Sr,Ca,Yb and Eu).Sci Rep,2012,2:426,ar Xiv:1202.4340
44 Mizuguchi Y,Hara Y,Deguchi K,et al.Anion height dependence of Tcfor the Fe-based superconductor.Supercond Sci Technol,2010,23:054013,ar Xiv:1001.1801
45 Lu X F,Wang N Z,Zhang G H,et al.Superconductivity in Li Fe O2Fe2Se2with anti-Pb O-type spacer layers.Phys Rev B,2014,89:020507,ar Xiv:1309.3833
46 Lu X F,Wang N Z,Luo X G,et al.Superconductivity and phase diagram of(Li0.8Fe0.2)OHFeSe1-xSx.Phys Rev B,2014,90:214520,ar Xiv:1501.01157
47 Sugai S,Mizuno Y,Kiho K,et al.Pairing symmetry of the multiorbital pnictide superconductor Ba Fe1.84Co0.16As2from Raman scattering.Phys Rev B,2010,82:140504
48 Sugai S,Mizuno Y,Watanabe R,et al.Spin-density-wave gap with Dirac nodes and two-magnon Raman scattering in Ba Fe2As2.J Phys Soc Jpn,2012,81:024718,ar Xiv:1201.5207[]
49 Han M J,Yin Q,Pickett W E,et al.Anisotropy,itineracy,and magnetic frustration in high-Tciron pnictides.Phys Rev Lett,2009,102:107003,ar Xiv:0811.0034
50 Han M J,Savrasov S Y.Doping driven(π,0)nesting and magnetic properties of Fe1+xTe superconductors.Phys Rev Lett,2009,103:067001
51 Zhao J,Adroja D T,Yao D X,et al.Spin waves and magnetic exchange interactions in Ca Fe2As2.Nat Phys,2009,5:555-560,ar Xiv:0903.2686
52 Sugai S,Suzuki H,Takayanagi Y,et al.Carrier-density-dependent momentum shift of the coherent peak and the LO phonon mode in p-type high-Tcsuperconductors.Phys Rev B,2003,68:184504
53 Zhang A M,Xiao J H,Li Y S,et al.Two-magnon Raman scattering in A0.8Fe1.6Se2systems(A=K,Rb,Cs,and Tl):Competition between superconductivity and antiferromagnetic order.Phys Rev B,2012,85:214508,ar Xiv:1106.2706
54 Yan X W,Gao M,Lu Z Y,et al.Ternary iron selenide K0.8Fe1.6Se2is an antiferromagnetic semiconductor.Phys Rev B,2011,83:233205,ar Xiv:1102.2215
55 Lei B,Xiang Z J,Lu X F,et al.Gate-tuned superconductor-insulator transition in(Li,Fe)OHFeSe.Phys Rev B,2016,93:060501,ar Xiv:1503.02457
56 Jovanovi?V P,Fruchter L,Li Z Z,et al.Anisotropy of the in-plane angular magnetoresistance of electron-doped Sr1-xLaxCu O2thin films.Phys Rev B,2010,81:134520,ar Xiv:1004.4163
57 Fang M H,Pham H M,Qian B,et al.Superconductivity close to magnetic instability in Fe(Se1-xTex)0.82.Phys Rev B,2008,78:224503,ar Xiv:0807.4775
58 Yeh K W,Huang T W,Huang Y,et al.Tellurium substitution effect on superconductivity of theα-phase iron selenide.Europhys Lett,2008,84:37002,ar Xiv:0808.0474
59 Martinelli A,Palenzona A,Tropeano M,et al.From antiferromagnetism to superconductivity in Fe1+yTe1-xSex(0≤x≤0.20):Neutron powder diffraction analysis.Phys Rev B,2010,81:094115,ar Xiv:1002.3517
60 Bao W,Qiu Y,Huang Q,et al.Tunable(δπ,δπ)-type antiferromagnetic order inα-Fe(Te,Se)superconductors.Phys Rev Lett,2009,102:247001
61 Li S,de La Cruz C,Huang Q,et al.First-order magnetic and structural phase transitions in Fe1+ySexTe1-x.Phys Rev B,2009,79:054503,ar Xiv:0811.0195
62 Ksenofontov V,Wortmann G,Chumakov A I,et al.Density of phonon states in superconducting FeSe as a function of temperature and pressure.Phys Rev B,2010,81:184510,ar Xiv:1004.2007
63 Mc Queen T M,Huang Q,Ksenofontov V,et al.Extreme sensitivity of superconductivity to stoichiometry in Fe1+δSe.Phys Rev B,2009,79:014522,ar Xiv:0811.1613
64 Phelan D,Millican J N,Thomas E L,et al.Neutron scattering measurements of the phonon density of states of FeSe1-xsuperconductors.Phys Rev B,2009,79:014519,ar Xiv:0811.1215
65 Homes C C,Dai Y M,Schneeloch J,et al.Phonon anomalies in some iron telluride materials.Phys Rev B,2016,93:125135,ar Xiv:1602.08077
66 Xu B,Dai Y M,Shen B,et al.Anomalous phonon redshift in K-doped Ba Fe2As2iron pnictides.Phys Rev B,2015,91:104510,ar Xiv:1503.03838
67 Zhang Y,Chen F,He C,et al.Strong correlations and spin-density-wave phase induced by a massive spectral weight redistribution inα-Fe1.06Te.Phys Rev B,2010,82:165113
68 Lin P H,Texier Y,Taleb-Ibrahimi A,et al.Nature of the bad metallic behavior of Fe1.06Te inferred from its evolution in the magnetic state.Phys Rev Lett,2013,111:217002,ar Xiv:1306.2603
69 Stewart G R.Superconductivity in iron compounds.Rev Mod Phys,2011,83:1589-1652,ar Xiv:1106.1618
70 Fernandes R M,Chubukov A V,Schmalian J.What drives nematic order in iron-based superconductors?Nat Phys,2014,10:97-104
71 Chu J H,Analytis J G,De Greve K,et al.In-plane resistivity anisotropy in an underdoped iron arsenide superconductor.Science,2010,329:824-826
72 Tanatar M A,Blomberg E C,Kreyssig A,et al.Uniaxial-strain mechanical detwinning of Ca Fe2As2and Ba Fe2As2crystals:Optical and transport study.Phys Rev B,2010,81:184508,ar Xiv:1002.3801
73 Knolle J,Eremin I,Akbari A,et al.Nematic electronic structure in the“parent”state of the iron-based superconductor Ca(Fe1-xCox)2As2.Science,2010,327:181-184
74 Yi M,Lu D,Chu J H,et al.Symmetry-breaking orbital anisotropy observed for detwinned Ba(Fe1-xCox)2As2above the spin density wave transition.Proc Natl Acad Sci USA,2011,108:6878-6883,ar Xiv:1011.0050
75 Kasahara S,Shi H J,Hashimoto K,et al.Electronic nematicity above the structural and superconducting transition in Ba Fe2(As1-xPx)2.Nature,2012,486:382-385
76 Shimojima T,Sonobe T,Malaeb W,et al.Pseudogap formation above the superconducting dome in iron pnictides.Phys Rev B,2014,89:045101,ar Xiv:1305.3875
77 Zhang Y,He C,Ye Z R,et al.Symmetry breaking via orbital-dependent reconstruction of electronic structure in detwinned Na Fe As.Phys Rev B,2012,85:085121,ar Xiv:1111.6430
78 Yi M,Lu D H,Moore R G,et al.Electronic reconstruction through the structural and magnetic transitions in detwinned Na Fe As.New J Phys,2012,14:073019,ar Xiv:1111.6134
79 Rosenthal E P,Andrade E F,Arguello C J,et al.Visualization of electron nematicity and unidirectional antiferroic fluctuations at high temperatures in Na Fe As.Nat Phys,2014,10:225-232,ar Xiv:1307.3526
80 Nakayama K,Miyata Y,Phan G N,et al.Reconstruction of band structure induced by electronic nematicity in an FeSe superconductor.Phys Rev Lett,2014,113:237001,ar Xiv:1404.0857
81 Watson M D,Kim T K,Haghighirad A A,et al.Emergence of the nematic electronic state in FeSe.Phys Rev B,2015,91:155106,ar Xiv:1502.02917
82 Zhang P,Qian T,Richard P,et al.Observation of two distinct dxz/dyzband splittings in FeSe.Phys Rev B,2015,91:214503
83 Fedorov A,Yaresko A,Kim T K,et al.Effect of nematic ordering on electronic structure of FeSe.Sci Rep,2016,6:36834,ar Xiv:1606.03022
84 Huynh K K,Tanabe Y,Urata T,et al.Electric transport of a single-crystal iron chalcogenide FeSe superconductor:Evidence of symmetrybreakdown nematicity and additional ultrafast Dirac cone-like carriers.Phys Rev B,2014,90:144516,ar Xiv:1405.3815
85 Mc Queen T M,Williams A J,Stephens P W,et al.Tetragonal-to-orthorhombic structural phase transition at 90 K in the superconductor Fe1.01Se.Phys Rev Lett,2009,103:057002,ar Xiv:0905.1065
86 B?hmer A E,Arai T,Hardy F,et al.Origin of the tetragonal-to-orthorhombic phase transition in FeSe:A combined thermodynamic and NMRstudy of nematicity.Phys Rev Lett,2015,114:027001,ar Xiv:1407.5497
87 B?hmer A E,Hardy F,Eilers F,et al.Lack of coupling between superconductivity and orthorhombic distortion in stoichiometric singlecrystalline FeSe.Phys Rev B,2013,87:180505,ar Xiv:1303.2026
88 Wang Q,Shen Y,Pan B,et al.Strong interplay between stripe spin fluctuations,nematicity and superconductivity in FeSe.Nat Mater,2016,15:159-163,ar Xiv:1502.07544
89 Shamoto S,Matsuoka K,Kajimoto R,et al.Spin nematic susceptibility studied by inelastic neutron scattering in FeSe,ar Xiv:1511.04267
90 Baek S H,Efremov D V,Ok J M,et al.Orbital-driven nematicity in FeSe.Nat Mater,2015,14:210-214,ar Xiv:1408.1875
91 Wang F,Kivelson S A,Lee D H.Nematicity and quantum paramagnetism in FeSe.Nat Phys,2015,11:959-963,ar Xiv:1501.00844
92 Glasbrenner J K,Mazin I I,Jeschke H O,et al.Effect of magnetic frustration on nematicity and superconductivity in iron chalcogenides.Nat Phys,2015,11:953-958,ar Xiv:1501.04946
93 Yu R,Si Q.Antiferroquadrupolar and ising-nematic orders of a frustrated bilinear-biquadratic heisenberg model and implications for the magnetism of FeSe.Phys Rev Lett,2015,115:116401,ar Xiv:1501.05926
94 Luo C W,Chung C P,Wang S H,et al.Unveiling the hidden nematicity and spin subsystem in FeSe.npj Quant Mater,2017,2:32,ar Xiv:1603.08710
95 Massat P,Farina D,Paul I,et al.Charge-induced nematicity in FeSe.Proc Natl Acad Sci USA,2016,113:9177-9181,ar Xiv:1603.01492
96 Locquet J P,Perret J,Fompeyrine J,et al.Doubling the critical temperature of La1.9Sr0.1Cu O4using epitaxial strain.Nature,1998,394:453-456
97 Strongin M,Kammerer O F,Crow J E,et al.Enhanced superconductivity in layered metallic films.Phys Rev Lett,1968,21:1320-1323
98 Wang Q Y,Li Z,Zhang W H,et al.Interface-induced high-temperature superconductivity in single unit-cell FeSe films on Sr Ti O3.Chin Phys Lett,2012,29:037402,ar Xiv:1201.5694
99 Ge J F,Liu Z L,Liu C,et al.Superconductivity above 100 K in single-layer FeSe films on doped Sr Ti O3.Nat Mater,2015,14:285-289,ar Xiv:1406.3435
100 Zhang W,Li Z,Li F,et al.Interface charge doping effects on superconductivity of single-unit-cell FeSe films on Sr Ti O3substrates.Phys Rev B,2014,89:060506
101 Lee J J,Schmitt F T,Moore R G,et al.Interfacial mode coupling as the origin of the enhancement of Tcin FeSe films on Sr Ti O3.Nature,2014,515:245-248,ar Xiv:1312.2633
102 Peng R,Xu H C,Tan S Y,et al.Tuning the band structure and superconductivity in single-layer FeSe by interface engineering.Nat Commun,2014,5:5044
103 Peng R,Shen X P,Xie X,et al.Measurement of an enhanced superconducting phase and a pronounced anisotropy of the energy gap of a strained FeSe single layer in FeSe/Nb:Sr Ti O3/KTa O3heterostructures using photoemission spectroscopy.Phys Rev Lett,2014,112:107001
104 Zhang W H,Sun Y,Zhang J S,et al.Direct observation of high-temperature superconductivity in one-unit-cell FeSe films.Chin Phys Lett,2014,31:017401,ar Xiv:1311.5370
105 Zhang Z,Wang Y H,Song Q,et al.Onset of the Meissner effect at 65 K in FeSe thin film grown on Nb-doped Sr Ti O3substrate.Sci Bull,2015,60:1301-1304
106 Deng L Z,Lv B,Wu Z,et al.Meissner and mesoscopic superconducting states in 1-4 unit-cell FeSe films.Phys Rev B,2014,90:214513,ar Xiv:1311.6459
107 Sun Y,Zhang W,Xing Y,et al.High temperature superconducting FeSe films on Sr Ti O3substrates.Sci Rep,2015,4:6040,ar Xiv:1404.3464
108 Cui Y T,Moore R G,Zhang A M,et al.Interface ferroelectric transition near the gap-opening temperature in a single-unit-cell FeSe film grown on Nb-Doped Sr Ti O3substrate.Phys Rev Lett,2015,114:037002
109 Fleury P A,Scott J F,Worlock J M.Soft phonon modes and the 110 K phase transition in Sr Ti O3.Phys Rev Lett,1968,21:16-19
110 Bianchi U,Kleemann W,Bednorz J G.Raman scattering of ferroelectric Sr1-xCaxTi O3,x=0.007.J Phys-Condens Matter,1994,6:1229-1238
111 Scott J F.Interpretation of phonon anomalies in Sr Ti O3near 37 K.Ferroelectrics Lett Sect,1995,20:89-95
112 Taniguchi H,Yagi T,Takesada M,et al.Isotope effect on the soft-mode dynamics of Sr Ti O3studied by Raman scattering.Phys Rev B,2005,72:064111
113 Taniguchi H,Itoh M,Yagi T.Ideal soft mode-type quantum phase transition and phase coexistence at quantum critical point in18O-exchanged Sr Ti O3.Phys Rev Lett,2007,99:017602
114 Zhong W,Vanderbilt D.Competing structural instabilities in cubic perovskites.Phys Rev Lett,1995,74:2587-2590
115 Müller K A,Burkard H.Sr Ti O3:An intrinsic quantum paraelectric below 4 K.Phys Rev B,1979,19:3593-3602
116 Rowley S E,Spalek L J,Smith R P,et al.Ferroelectric quantum criticality.Nat Phys,2014,10:367-372,ar Xiv:0903.1445
117 Fleury P A,Worlock J M.Electric-field-induced Raman scattering in Sr Ti O3and KTa O3.Phys Rev,1968,174:613-623
118 Itoh M,Wang R,Inaguma Y,et al.Ferroelectricity induced by oxygen isotope exchange in strontium titanate perovskite.Phys Rev Lett,1999,82:3540-3543
119 Nilsen W G,Skinner J G.Raman spectrum of strontium titanate.J Chem Phys,1968,48:2240-2248
120 Uwe H,Yamaguchi H,Sakudo T.Ferroelectric microregion in KTa1-xNbxO3and Sr Ti O3.Ferroelectrics,1989,96:123-126