Title
<研究ノート>鉄系超伝導体BaFe[2](As[1-x]Px)[2]にみる非
ブエルミ液体的電子輸送現象と量子臨界点的振る舞い
Author(s)
笠原, 成
Citation
低温物質科学研究センター誌 : LTMセンター誌 (2010),
17: 10-18
Issue Date
2010-12-01
URL
https://doi.org/10.14989/153265
Right
Type
Departmental Bulletin Paper
㕲⣔㉸ఏᑟయBaFe
2(As
1-xP
x)
2ࡳࡿ㠀ࣇ࢙࣑ࣝᾮయⓗ㟁Ꮚ㍺㏦⌧㇟
㔞Ꮚ⮫⏺Ⅼⓗࡿ⯙࠸
Non-Fermi Liquid Charge Transport Properties and Quantum Critical Point
Behaviors as Seen in BaFe
2(As
1-xP
x)
2Iron-Pnictide Superconductor
➟ཎ ᡂ
ி㒔Ꮫప ≀㉁⛉Ꮫ◊✲ࢭࣥࢱ࣮
Shigeru Kasahara
Research Center for Low Temperature and Materials Sciences, Kyoto University
Non-Fermi liquid like charge transport properties and quantum critical behaviors observed in high-quality single crystals of BaFe2(As1-xPx)2 are reviewed. Near the SDW end point, charge transport coefficients, including
resistivity, Hall coefficient and magnetoresistance, exhibit striking deviations from the conventional Fermi liquid properties. De Haas-van Alphen effect measurements in a wide range of superconducting dome reveal that the volume of the Fermi surfaces shrink and the effective masses are enhanced as x approaches the critical concentration with highest Tc.. It is also shown that antiferromagnetic fluctuations deduced from 31P-NMR
measurements are notably enhanced near this optimal composition, where magnetically ordered temperature T deduced from relaxation rate is found to vanish. It is likely that these trends originate from the many-body interaction which gives rise to high-temperature superconductivity in iron-pnictides.
㸬ࡣࡌࡵ 㖡㓟≀ࡸ㔜࠸㟁Ꮚ⣔ྜ≀࡞, ᙉ┦㛵㟁Ꮚ⣔⨨࡙ࡅࡽࢀࡿ≀㉁࡛ࡣ, ᚑ᮶ࡢࣇ࢙࣑ࣝᾮయ ㄽࡽࡁࡃ㐓⬺ࡋࡓ㍺㏦⌧㇟ࡀࡋࡤࡋࡤぢฟࡉࢀ࡚࠸ࡿ㸬≉, ࡇࡢࡼ࠺࡞㠀ࣇ࢙࣑ࣝᾮయⓗ࡞㍺ ㏦⌧㇟ࡣ, ᙉ☢ᛶࡸᙉ☢ᛶ⛛ᗎࡀᾘኻࡍࡿ࠸ࢃࡺࡿ“㔞Ꮚ⮫⏺Ⅼ”ࡢ㏆ഐ࡛ከࡃほ ࡉࢀ, ᙉ࠸☢Ẽ ᦂࡽࡂࡼࡗ࡚‽⢏Ꮚࡢ᭷ຠ㉁㔞ࡸᩓ᩿㠃✚ࡀࡁ࡞ኚㄪࢆཷࡅࡿࡇࡀ㆟ㄽࡉࢀ࡚࠸ࡿ㸬ࡉࡽ ⯆῝࠸ࡇ, ࡇࡢࡼ࠺࡞㠀ࣇ࢙࣑ࣝᾮయⓗ㍺㏦⌧㇟ࢆ♧ࡍ⣔ࡣ㉸ఏᑟ≧ែࢆ♧ࡍ≀㉁ࡀከࡃⓎ ぢࡉࢀ࡚࠾ࡾ, 㟁Ꮚ⣔ࡢᙉ࠸┦స⏝ࢆᫎࡋ࡚, ㉸ఏᑟ⛛ᗎ㛵ᩘࡀᚑ᮶ࡢ BCS ㉸ఏᑟࡣ␗࡞ࡿ㠀 ᚑ᮶ᆺ㉸ఏᑟࡀฟ⌧ࡍࡿࡇࡀከࡃぢฟࡉࢀ࡚ ࠸ࡿ㸬ᙉ┦㛵㟁Ꮚ⣔࠾ࡅࡿ㠀ࣇ࢙࣑ࣝᾮయⓗ࡞ ᣲືࡣ, 㔞Ꮚ⮫⏺Ⅼࡸ㠀ᚑ᮶ᆺࡢ㉸ఏᑟࡢⓎ⌧ ᶵᵓ῝ࡃ㛵ࡗࡓ㔜せ࡞ၥ㢟࡞ࡗ࡚࠸ࡿ㸬 ᮏ✏࡛⤂ࡍࡿ㕲◉⣲⣔ྜ≀࠾ࡅࡿ㉸ఏ ᑟࡣ, 2008 ᖺࡢ㕲࢜࢟ࢩࢽࢡࢱࢻ LaFeAs(O,F) ࠾ࡅࡿ㉸ఏᑟⓎぢࢆ➃ࡍࡿ᪂ࡋ࠸⣔࡛࠶ࡿ [1]㸬ࡑࡢᚋ, ḟࠎ㢮⦕ᵓ㐀≀㉁࡛ࡢ㉸ఏᑟࡀⓎ ぢࡉࢀ, ㉸ఏᑟ㌿⛣ ᗘ(Tc)ࡣⓎぢࡽഹᩘࣨ ᅗ 1. BaFe2As2⣔ࡢඖ⣲⨨┦ᅗ. (Ba1-xKx)Fe2As2 hole doping Ba(Fe1-䡕Co䡕)2As2 electron doping 2y BaFe2As2 x SC BaFe2(As1-xPx)2 “Isovalent doping” SC SC T -1 -0.8 -0.6 -0.4 -0.2 0.2 0.4 0.6 0.8 1 50 100 150 0 SDW Ba As Fe
᭶࡛ 55 K ࡲ࡛⮳ࡗ࡚࠸ࡿ㸬ࡇࢀࡣ㖡㓟≀ࢆ㝖࠸ࡓ㉸ఏᑟయࡢ୰࡛᭱ࡶ㧗࠸್࡛࠶ࡾ, 㕲ࢽࢡࢱ ࢻࡀ᪂ࡋ࠸㧗 ㉸ఏᑟ≀㉁య⣔࡛࠶ࡿࡇࡣ᫂ࡽ࡛࠶ࡿ㸬㕲⣔㉸ఏᑟయ࠾ࡅࡿ㧗࠸ Tc࡛ࡢ㟁Ꮚᑐ ᙧᡂࡘ࠸࡚Ⓨ⌧ᶵᵓࢆ⌮ゎࡋ, ཪ, ࡑࡢඛ, ࡼࡾ㧗 ࡛ࡢ㉸ఏᑟࡢྍ⬟ᛶࢆ᥈ࡿୖ࡛ࡶ, ≀⌮ⓗ ㉳ࡁ࡚࠸ࡿ㇟ࢆ᫂ࡽࡍࡿࡇࡀྍḞ࡞ࡿ㸬≉ࡇࡢ⣔࡛ࡣ, ୍㒊ࡢእࢆ㝖ࡁ, ẕ≀㉁ࡀඹ ㏻ࡋ࡚ṇ᪉ᬗࡽᩳ᪉ᬗࡢᵓ㐀┦㌿⛣ᙉ☢ᛶⓗࢫࣆࣥᐦᗘἼ(SDW)ࡢ┦㌿⛣ࢆ♧ࡋ, ࡇࢀ 㞄᥋ࡋ࡚㉸ఏᑟࡀฟ⌧ࡍࡿ㸬⌮ㄽⓗࡣ, ࡇࡢ⣔ඹ㏻ࡋ࡚Ꮡᅾࡍࡿ࣮࣍ࣝ㟁Ꮚࡽ࡞ࡿ㠀㐃⤖ࣇ ࢙࣑ࣝ㠃㛫࡛ࡢࢿࢫࢸࣥࢢ⏤᮶ࡋࡓᙉ☢ᛶᦂࡽࡂࢆࡋ࡚, ྛࣇ࢙࣑ࣝ㠃㛫࡛㉸ఏᑟ⛛ᗎ㛵ᩘ ࡢ➢ྕࡀ␗࡞ࡗࡓ s±≧ែࡤࢀࡿ᪂ࡋ࠸㉸ఏᑟᑐ≧ែࡀⓎぢᚋࡲࡶ࡞ࡃᥦࡉࢀ࡚࠸ࡿ[2,3]㸬ࡇࡢ ࡼ࠺࡞ᦂࡽࡂ㉸ఏᑟࡢ┦㛵ࢆㄪࡿୖ࡛ࡶ, ᖖఏᑟ≧ែࡢ㍺㏦⌧㇟ࡀᚑ᮶ࡢࣇ࢙࣑ࣝᾮయⓗ࡞ࡶࡢ , ࡑࢀࡶࡇࢀࡽࡽࡁࡃእࢀࡓ㠀ࣇ࢙࣑ࣝᾮయⓗᣲືࢆ♧ࡍࡢࡣ㔜せ࡞ၥ㢟࡞ࡗ࡚࠸ࡿ㸬 ᵝࠎ࡞㢮⦕ᵓ㐀ࢆ⯙ྎ㉳ࡇࡿ㕲⣔㉸ఏᑟࡢ≀⌮ࢆ⌮ゎࡍࡿⅭࡣ, ࡑࡢ୰ࡽ᫂ᛌ࡞ࣔࢹࣝ≀㉁ ࡞ࡿࡶࡢࢆぢฟࡋ, ୟࡘ, ≀⌮ࡢᮏ㉁ࢆࡍࡇࡢ࡞࠸⣧Ⰻ࡞༢⤖ᬗࢆ⯙ྎࡋࡓ㆟ㄽࡀྍ㑊
࡞ࡿ㸬ࡇࡢほⅬࡽ AEFe2As2 (AE = Ba, Sr, Ca)ࢆẕ≀㉁ࡋࡓ“122”⣔㕲ࢽࢡࢱࢻࡣ༢⤖ᬗヨᩱࢆᚓ
ࡸࡍࡃ, 㕲⣔㉸ఏᑟࢆ⌮ゎࡍࡿⅭࡢ㔜せ࡞⣔ࡋ࡚άⓎ◊✲ࡀ࡞ࡉࢀ࡚࠸ࡿ㸬ᅗ 1 ࡣ BaFe2As2ࢆẕ ≀㉁ࡋࡓ௦⾲ⓗඖ⣲⨨ຠᯝࡢᴫ␎ᅗ࡛࠶ࡿ㸬Ba ࢧࢺࢆ K ࡛⨨ࡍࡿࡇࡼࡾ࣮࣍ࣝࡀ, Fe ࢧ ࢺࢆ Co ➼⨨ࡍࡿࡇࡼࡾ㟁Ꮚࡀ࢟ࣕࣜࡋ࡚ࢻ࣮ࣉࡉࢀ, ࡇࢀకࡗ࡚ᵓ㐀┦㌿⛣ SDW㌿⛣ࡀᢚไࡉࢀ㉸ఏᑟࡀฟ⌧ࡍࡿ[4,5]㸬ࡇࡢ, ࡇࡢ⣔࡛ࡣẕ≀㉁ࡢᅽຊ༳ຍࡼࡗ࡚ࡶ㉸ఏ ᑟࡀㄏ㉳ࡉࢀࡿࡇࡀ▱ࡽࢀ࡚࠾ࡾ[6], ᭦, ඖ⣲⨨࠾࠸࡚ࡶ As ࢧࢺࢆ➼ཎᏊ౯ࡢ P ࡛⨨ࡁ ࠼ࡿࡇ࡛Ꮫⓗᅽຊࡀ⣔ᑟධࡉࢀ㉸ఏᑟࡀฟ⌧ࡍࡿ[7]㸬ཪ, Fe 㠃ෆࢆ Ru ࡛⨨ࡋࡓሙྜࡶ㉸ ఏᑟࡀฟ⌧ࡍࡿࡇࡀ▱ࡽࢀ࡚࠸ࡿ[8]㸬➹⪅ࡽࡣࡇࡢ࠺ࡕ BaFe2(As1-xPx)2╔┠ࡋ, ⣧Ⰻ༢⤖ᬗࡢస 〇ᖖఏᑟ≧ែ࡛ࡢ㍺㏦⌧㇟, ㉸ఏᑟࢠࣕࢵࣉᵓ㐀㛵ࡍࡿᐇ㦂ࢆ⾜࡞ࡗ࡚ࡁࡓ[9-18]㸬➼ཎᏊ౯ࡢඖ ⣲⨨࡛ SDW ┦ࡽ㉸ఏᑟ┦ࡲ࡛ᇶᗏ≧ែࢆኚྍ⬟࡞ࡇࡢ⣔ࡣ, ࡢ࢟ࣕࣜࢻ࣮ࣉㄏ㉳ࡢࡶࡢ ࡣ␗࡞ࡾ, x ࡢ್ࡼࡽࡎ⿵ൾ㔠ᒓ᮲௳ࡀᡂࡾ ❧ࡕ, 㕲⣔㉸ఏᑟయࡢ㍺㏦⌧㇟࡞ࢆ㆟ㄽࡍࡿ ୖ࡛㔜せ࡞ࣔࢹࣝ≀㉁࡞ࡿ㸬ࡑࡢ᭱㐺⨨ヨᩱ ࡛ࡢ㉸ఏᑟ㌿⛣ࡣ㕲⣔㉸ఏᑟయࡢ୰࡛ࡶᴟࡵ࡚ ᛴᓧ࡛࠶ࡾ, ᭦, ㉸ఏᑟࢆㄏ㉳ࡍࡿⅭࡣඖ⣲ ⨨ࡀᚲせ࡞㕲◉⣲⣔ࡢ㉸ఏᑟయࡢ୰࠶ࡗ࡚, ᗈ࠸⨨⠊ᅖ࡛☢Ẽ㔞Ꮚື(dHvA ື)ࡀほ ࡉࢀࡿࡢ⣧Ⰻࡉࢆ♧ࡍ㸬ᚑࡗ࡚, ࡇࡢ⣔ࡣ㕲 ⣔㉸ఏᑟࡢ≀⌮ࢆ⌮ゎࡍࡿୖ࡛ᴟࡵ࡚ዲ㐺࡞⣔ ࡛࠶ࡿゝ࠼ࡿ㸬ᮏ✏࡛ࡣ➼ཎᏊ౯ඖ⣲⨨⣔࡛ ࠶ࡿ BaFe2(As1-xPx)2ࢆࣔࢹࣝ≀㉁ࡋ࡚, 㠀ࣇ࢙ ࣑ࣝᾮయⓗ㍺㏦⌧㇟㔞Ꮚ⮫⏺Ⅼⓗ࡞ࡿ⯙࠸ ࢆ⤂ࡋࡓ࠸㸬 㸬%D)H $V[3[ ༢⤖ᬗࡢ┦ᅗ ࡇࡢ⣔࡛ࡢ␗ᖖ࡞㍺㏦⌧㇟ࡘ࠸࡚㏙ࡿ๓ , ࡲࡎࡣ┦ᅗࡘ࠸࡚ゐࢀ࡚࠾ࡁࡓ࠸㸬ᅗ 2(a) ཬࡧ(b)ࡣ BaFe2(As1-xPx)2ࡢྛ⤌ᡂヨᩱ࠾ࡅࡿ㠃 0 10 20 30 40 0 20 40 60 80 -6 -5 -4 -3 -2 -1 0 Uxx (P: cm) T (K) 4S M (G) 0 20 40 60 80 100 0 100 200 300 T (K) Uxx (P: cm) 0 100 200 300 0 200 400 600 T (K) Uxx (P: cm) 0 100 200 300 100 101 102 RH (10 -3 cm 3/C) T (K) x = 0 0.07 0.14 0.20 0.23 0.27 0.33 0.41 0.56 0.64 0.71 (a) (c) 300 Pm (d) x = 0.33 (b) x = 0 0.14 0.20 0.33 0.41 0.64 T0 TSDW Tcon ᅗ 2: (a)-(b)BaFe2(As1-xPx)2 ༢⤖ᬗࡢUxx(T)᭤⥺. (b)x=0.33 ࡛ࡢ Tc㏆ഐࡢUxx(T)ཬࡧ M(T)᭤⥺㸬(d) ྛ⨨㔞ࡢヨᩱ࠾ࡅࡿ RH(T) [9].
ෆ㟁Ẽᢠ⋡ࡢ ᗘ౫ᏑᛶUxx(T)࡛࠶ࡿ㸬x = 0 ࡢ BaFe2As2࡛ࡣ, T0 = TSDW = 137 K ࠾࠸࡚ᵓ㐀ཬ ࡧ SDW ࡢྠ㌿⛣క࠺␗ᖖࡀぢࡽࢀࡿ㸬As ࢧࢺࡢ P ඖ⣲ࡢ⨨ࡼࡾ, ࡇࡢᵓ㐀/☢Ẽ ┦㌿⛣ࡣప ഃᢚไࡉࢀ, ࡑࢀࡒࢀ T0࠾ ࡅࡿUxx(T)ࡢቑ, TSDW࠾ࡅࡿࣆ࣮ࢡᵓ㐀 ࠸࠺ᙧ࡛⌧ࢀࡿ㸬ྠᵝࡢࡿ⯙࠸ࡣ㟁Ꮚࢻ࣮ࣉᆺ ࡢ Ba(Fe1-xCox)2As2࠾࠸࡚ࡶሗ࿌ࡉࢀ࡚࠸ࡿࡀ, ᵓ㐀/☢Ẽ┦㌿⛣ࡼࡾప ࡛ࡶUxx(T)ࡀῶᑡࡋ࡚࠸ ࡃᵝᏊࡣከᑡ␗࡞ࡿ[19-21]㸬x ~ 0.2 ⛬ᗘ࠾࠸࡚㉸ఏᑟࡼࡿࢮࣟᢠࡀほ ࡉࢀ, x > 0.3 ࡛ᵓ㐀/☢ Ẽ┦㌿⛣ࡀぢࡽࢀࡎ Tc Ә Tcmax 31 Kࡢ㉸ఏᑟ㌿⛣ࢆ♧ࡍ㸬ᅗ 2(c)ࡣ㉸ఏᑟ㌿⛣㏆ഐ࠾ࡅࡿUxx(T), dc☢ࡢ ᗘ౫Ꮡᛶ M(T)࡛࠶ࡿ㸬㉸ఏᑟ㌿⛣ࡣᴟࡵ࡚ᛴᓧ࡛࠶ࡾ, ᩘከࡃࡢ㕲⣔㉸ఏᑟయࡢ୰࡛ࡶ᭱ Ⰻࡢࡶࡢ࡛࠶ࡿ㸬ࡼࡾ㧗⃰ᗘࡢ P ⨨ࡼࡗ࡚ Tcࡣᚎࠎపୗࡋ, x ~ 0.71 ⛬ᗘ࠾࠸࡚㉸ఏᑟ┦ࡀᾘ ኻࡍࡿ㸬ᅗ 2(d)ࡣ࣮࣍ࣝಀᩘࡢ ᗘ౫Ꮡᛶ RH(T)࡛࠶ࡿ㸬ࡢ⤌ᡂࡢヨᩱࡘ࠸࡚ࡶ RH(T)ࡣ㈇ࡢ್࡛ ࠶ࡾ, ࢟ࣕࣜࢆᨭ㓄ࡋ࡚࠸ࡿࡢࡣ㟁Ꮚ࡛࠶ࡿ㸬P ⨨㔞ࡀᑡ࡞࠸ヨᩱ࡛ࡣ, TSDW࠾࠸࡚ RH(T) ࡁ࡞ቑࡀࡳࡽࢀ, ࡇࢀࡣࣇ࢙࣑ࣝ㠃࠾࠸࡚ SDW ࢠࣕࢵࣉࡀᙧᡂࡉࢀ࡚࠸ࡿࡇࢆᫎࡋ࡚࠸ࡿ ⪃࠼ࡽࢀࡿ㸬ࡓࡔࡋ, RH(T)ࡣ㠀☢ᛶ≧ែ࠾࠸࡚ࡶᙉ࠸ ᗘ౫Ꮡᛶࢆ♧ࡋ࡚࠸ࡿࡇὀ┠ࡋ࡚࠾ ࡁࡓ࠸㸬 ᅗ 3 ࡣUxx(T)ࡼࡾỴᐃࡋࡓ BaFe2(As1-xPx)2ࡢ T-x ┦ᅗ࡛࠶ࡿ㸬0.14 Ә x Ә 0.71 ࡢᗈ࠸⨨⠊ᅖ࠾࠸ ࡚㉸ఏᑟ┦ࡀᏑᅾࡋ, 0.14 Ә x Ә 0.3 ࡛ࡣ SDW ㉸ఏᑟ, ୧⪅ࡢ┦㌿⛣ࡀࡳࡽࢀࡿ㸬x ~ 0.3 ࡢ㏆ഐ࠾ ࠸࡚ᵓ㐀/☢Ẽ┦㌿⛣ࡣᾘኻࡍࡿ㸬 㸬㠀ࣇ࢙࣑ࣝᾮయⓗ㍺㏦⌧㇟ ࡇࡇ࡛ὀ┠ࢆࡋࡓ࠸ࡢࡀᵓ㐀/☢Ẽ┦㌿ ⛣ࡢᢚไࡉࢀࡓ㠀☢ᛶᖖఏᑟ≧ែ࠾ࡅࡿ Uxx(T)ࡢኚ࡛࠶ࡿ㸬Tcࡀ್᭱ࢆ♧ࡍ᭱㐺 ⨨㏆ഐ, ༶ࡕ, ᵓ㐀/☢Ẽ┦㌿⛣ᾘኻࡢ┤ ㏆࡛ࡣ, Uxx(T)ࡀ ᗘࡢ୍ẚࡍࡿ␗ᖖ ࡞ࡿ⯙࠸(Uxx ~ T)ࡀほ ࡉࢀࡿ[ᅗ 4(a)]㸬 㟁Ẽᢠ⋡ࡢ ᗘኚࢆ Uxx(T) = U0 + AT (1) ⾲ࡍ 㸻1 ࡛࠶ࡾ, ࡇࢀࡣࣛࣥࢲ࢘ࡢࣇ ࢙࣑ࣝᾮయㄽ࠾࠸࡚㟁Ꮚ-㟁Ꮚᩓࡼ ࡗ࡚ᑟࢀࡿ 㸻1 ࡽࡁࡃ㐓⬺ࡋ࡚࠸ ࡿ㸬x ࡀࡁࡃ࡞ࡾ, Tcࡀపࡃ࡞ࡿ, ࡢ್ࡣ 2 ḟ➨㏆࡙ࡁ, ࣇ࢙࣑ࣝᾮయⓗ࡞ࡿ⯙࠸⛣ ⾜ࡍࡿ㸬ᅗ 3 ࡢ T-x ┦ᅗୖ, ࣋࢟ ࡢኚࢆ࣓࣮ࢪࣉࣟࢵࢺࡋ࡚⾲ࡋࡓ㸬x = 0.33 ࡢ᭱㐺⨨㏆ ഐࢆ୰ᚰ = 1.0 Æ 2.0 ࡢኚࡀప ࡽ V Ꮠ≧ᗈࡀࡗ࡚࠸ࡿ㸬ᑦ, ᭱㐺⨨㏆ഐࡢヨᩱ࠾࠸ ࡚ T > 150 K ࡢ㧗 ᇦ࡛Uxx ~ Tࡽഹࡎࢀጞࡵࡿୖฝࡢࡿ⯙࠸ࡀ⌧ࢀࡿࡀ, ࡇࢀࡣ࢟ࣕࣜࡢᩓ ᴟ㝈 Ioffery-Regel ᴟ㝈 ㏆࡙࠸࡚࠸ࡿࡓࡵࡳࡿࡇࡀ࡛ࡁࡿ㸬୍⯡㔠ᒓࡣ㧗 ࡛㟁Ẽᢠࡀ ᩓࡼࡗ࡚㣬ࡋ, ࡇࡢࡁ kFlmfp ~ 1ᙜࡓࡿ kFࡣࣇ࢙࣑ࣝἼᩘ, lmfpࡣ࢟ࣕࣜࡢᖹᆒ⮬⏤⾜⛬ 㸬 0 50 100 150 0 100 200 T (K) Uxx (P: cm) ~ T1.9 ~ T1.2 ~ T1.0 x = 0.33 x = 0.41 x = 0.64 ~ T2.0 x = 0.71 x = 0.56 ~ T1.7 0 50 100 1.5 2 2.5 3 RH (10 -3 cm 3/C) T (K) 0 0.1 0.2 0 0.005 0.01 0.015 'Uxx (H )/ Uxx (P0H/Uxx) 2 (T2/(P:cm)2) 40 K 50 K 60 K 80 K 100 K (a) (b) x = 0.33 'Uxx (H )/ Uxx tan24 H 0.01 0 0.001 0 ᅗ 4. (a)BaFe2(As1-xPx)2༢⤖ᬗࡢ㠀☢ᛶ㡿ᇦ(x > 0.3) ࠾ ࡅࡿUxx(T)᭤⥺. ᤄධᅗࡣ᭱㐺⨨ヨᩱ࡛ࡢ RH(T). (b)᭱ 㐺⨨ヨᩱ࡛ࡢ Uxx(H)/Uxx.[9]. TSD Tc T0 2.0 0 D 1.0 BaFe2(As1-xPx)2 m*/m _T_ 0 0.2 0.4 0.6 0 100 200 0 1 2 3 4 x T (K) m* /m b Superconductivity SDW TSD Tc T0 2.0 0 D 1.0 BaFe2(As1-xPx)2 m*/m _T_ 0 0.2 0.4 0.6 0 100 200 0 1 2 3 4 x T (K) m* /m b Superconductivity SDW ᅗ3: BaFe2(As1-xPx)2ࡢT-x┦ᅗ.
➨ 0 ㏆ఝࡋ࡚༢⣧࡞ḟඖࡢࣇ࢙࣑ࣝ㠃ࢆ⪃៖ࡍࡿ, ࡇࡢ⣔ࡢ 5 ࡘࡢࣇ࢙࣑ࣝ㠃ࡼࡿఏᑟᗘࡣV = 5×(e2/h)kFlmfpぢ✚ࡶࡽࢀ, U ~ 350 P:cm ࡛ kFlmfp ~ 1࡞ࡿ⪃࠼ࡽࢀࡿ[22]㸬 ୖ㏙ࡢࡼ࠺Uxx(T)ࡣ᭱㐺⨨㏆ഐ࡛ᚑ᮶ࡢࣇ࢙࣑ࣝᾮయⓗ㍺㏦⌧㇟ࡽ㐓⬺ࡋࡓࡿ⯙࠸ࢆ♧ࡍ㸬 ࡛ࡣ, ࡑࢀ௨እࡢ㍺㏦ಀᩘࡣ࠺࡛࠶ࢁ࠺㸬➨ࡢ㍺㏦⌧㇟ࡢ␗ᖖࡋ࡚, Uxx ~ Tࡀほ ࡉࢀࡿ⤌ᡂ ᇦ࡛ࡣ, 㠀☢ᛶᖖఏᑟ≧ែ࡛ࡶ࣮࣍ࣝಀᩘ RHࡀప ྥࡅ࡚, |RH(T)| = C1/T+C2࡛㏆ఝࡉࢀࡿࡼ࠺࡞ቑ ࢆ♧ࡍࡇࡀᣲࡆࡽࢀࡿ[ᅗ4(a)ᤄධᅗ]㸬ࡇࡢ ᗘ౫Ꮡᛶࡣxࡀࡁࡃ࡞ࡿᚑ࠸ᑠࡉࡃ࡞ࡗ࡚࠸ࡃ㸬 ࡇࡢࡼ࠺࡞Uxx,(T) RH(T)ࡢࡿ⯙࠸ࡣࡢ㕲⣔㉸ఏᑟయ࡛ࡶሗ࿌ࡉࢀ࡚࠸ࡿࡀ[19-21,23], 㕲⣔㉸ఏᑟయ ࡣ」ᩘࡢ㟁Ꮚ࠾ࡼࡧṇᏍࡼࡿࣇ࢙࣑ࣝ㠃ࢆᣢࡘ࣐ࣝࢳࣂࣥࢻ≀㉁࡛࠶ࡾ, ࡇࡢࡼ࠺࡞࣐ࣝࢳࣂࣥࢻ ⣔࡛ࡣ࣮࣍ࣝಀᩘࡀ ᗘ౫Ꮡࡋ࡚ࡶⰋ࠸ࡢ㆟ㄽࡀࡉࢀ࡚࠸ࡿ㸬࡛ࡣ, ୖグࡢࡼ࠺࡞ ᗘẚࡋ ࡓᢠ⋡ࡢኚࡸ࣮࣍ࣝಀᩘࡢቑࡣ, ᮏᙜᚑ᮶ࡢከࣂࣥࢻࡼࡿຠᯝ, ࡑࢀࡶ㕲⣔㉸ఏᑟయ ࡢ≉ᚩࢆᫎࡋࡓ㠀ᚑ᮶ᆺࡢ㍺㏦⌧㇟࡞ࡢ࡛࠶ࢁ࠺㸬 ࡲࡎ⡆༢࡞ࣔࢹࣝࡋ࡚㟁Ꮚ, ཬࡧ࣮࣍ࣝࡽ࡞ࡿ 2 ࣂࣥࢻࡢ⣔ࢆ⪃࠼ࡿ㸬 ➼ཎᏊ౯⨨⣔࡛࠶ࡿ BaFe2(As1-xPx)2ࡢሙྜ, ࢟ࣕࣜࢻ࣮ࣉࡼࡾ㉸ఏᑟࡀㄏ㉳ࡉࢀࡿࡶࡢࡣ␗࡞ࡾ, ࡢ⤌ᡂ࠾࠸࡚ ࡶ⣔ࡣ⿵ൾ㔠ᒓ᮲௳ࢆಖࡘ࠸࠺ᙉ࠸ไ⣙ࡀᏑᅾࡍࡿ㸬 ࡇࡢሙྜ, ࣮࣍ࣝಀᩘࡣ㟁Ꮚ ṇᏍ ࡢ㟁Ẽఏ ᑟᗘVe (Vh)ࢆ⏝࠸࡚ RH = 1/ne×(Vh - Ve)/(Vh + Ve)࠸࠺ࢩࣥࣉࣝ࡞ᙧ࡛グ㏙࡛ࡁࡿ㸬ࡇࡢᘧࡣ࠸࡞ࡿ≧ ἣ࡛ࡶ|RH| 1/ne ࡛࠶ࡿࡇࢆไ⣙ࡋ࡚࠾ࡾ, ࣮࣍ࣝಀᩘࡢ⤯ᑐ್㛵ࡋ࡚ୖ㝈ࢆ࠼ࡿࡇ࡞ࡿ㸬 ࡋࡋᐇ㦂࡛ほ ࡉࢀࡿ⤯ᑐ್ࡣࣂࣥࢻィ⟬ࡽぢ✚ࡽࢀࡿ࢟ࣕࣜ⃰ᗘ࡛ᮇᚅࡉࢀࡿࡶࡢࡼࡾࡶᩘ ಸࡁࡃ, ㏻ᖖࡢከࣂࣥࢻࡢຠᯝ࡛ࡣㄝ᫂ࡀᅔ㞴࡛࠶ࡿ[7]㸬ཪ, ヲ⣽࡞㆟ㄽࡣࡋ࡞࠸ࡀ, ௬ࡇࡢ⣔ࡢ ␗ᖖ࡞㍺㏦⌧㇟ࢆከࣂࣥࢻࡢຠᯝ࡛ㄝ᫂ࡋࡼ࠺ࡍࡿ࡞ࡽࡤ, ᗄࡘࡢ␗࡞ࡿࣂࣥࢻࡀࡑࢀࡒࢀ␗࡞ ࡿ ᗘ౫Ꮡᛶࢆ♧ࡋ, ᭦ࡑࢀࡀ࢟ࣕࣜࢻ࣮ࣉ࡛ㄏ㉳ࡉࢀࡿ㕲⣔㉸ఏᑟࡸ, ➼ཎᏊ౯⨨ࡸᅽຊㄏ ㉳ࡢ⣔, ࡑࢀ௨ୖᵝࠎ࡞␗࡞ࡿ㢮⦕ᵓ㐀≀㉁࡛ᡂࡾ❧ࡓࡘ࠸࠺⮬↛࡞௬ᐃࢆࡋ࡞ࡅࢀࡤ࡞ࡽ࡞ ࡃ࡞ࡗ࡚ࡋࡲ࠺㸬 ᭦, 㕲⣔㉸ఏᑟయࡢ␗ᖖ࡞ᖖఏᑟ≧ែࢆ≉ᚩࡅࡿ➨୕ࡢ㍺㏦⌧㇟ࡋ࡚☢Ẽᢠ⋡'Uxx(H)/Uxx = [Uxx(H) - Uxx(H=0)]/UxxҞ(H ࡀᣲࡆࡽࢀࡿ㸬ᚑ᮶ࡢࣇ࢙࣑ࣝᾮయ࡛ࡣ, 'Uxx(H)/Uxxࡣ࢟ࣕࣜࡢ㌶㐨ࡢ ᙙ᭤ຠᯝࡼࡗ࡚⏕ࡌ, ࢧࢡࣟࢺࣟࣥ࿘ἼᩘZcᩓ㛫Wࢆ⏝࠸࡚'Uxx(H)/Uxx = F(ZcW)࡞ࡿࢥ࣮ ࣮ࣛ๎ࡀᡂ❧ࡍࡿ㸬Zc ҃H, W҃Uxx-1࡛࠶ࡿࡽ, ࣇ࢙࣑ࣝᾮయ≧ែ࡛ࡣࢥ࣮࣮ࣛ๎ࡼࡗ࡚'Uxx(H)/Uxx = F(P0HUxx H ࡢࡼ࠺☢Ẽᢠࡀࢫࢣ࣮ࣝࡉࢀ࡞ࡃ࡚࠸ࡅ࡞࠸㸬ࡇࢀࢆ⏝࠸࡚ x = 0.33 ࡢ᭱㐺⨨ ヨᩱ࠾ࡅࡿ☢Ẽᢠࢆࣉࣟࢵࢺࡋࡓࡶࡢࡀᅗ 4(b)࡛࠶ࡿ㸬ྛ ᗘ࡛ࡢ'Uxx(H)/Uxxࡣࢫࢣ࣮ࣝࡉࢀ࡚ ࠸࡞࠸㸬᫂ࡽࢥ࣮࣮ࣛ๎ࡣ◚ࢀ࡚࠸ࡿ㸬ᐇࡣ, ࡇࡢࡼ࠺࡞㠀ࣇ࢙࣑ࣝᾮయⓗ㍺㏦⌧㇟ࢆ♧ࡍᙉ┦ 㛵㟁Ꮚ⣔࠾࠸࡚ࡣ, ☢Ẽᢠࡣ࣮࣍ࣝゅ4+>Ł tan-ң(Uxy/Uxx)]ࢆ⏝࠸࡚ࢫࢣ࣮ࣝࡉࢀ, 'Uxx(H)/Uxx ҃ tan24Hࡢᙧࡢಟṇࢥ࣮࣮ࣛ๎ࡀᡂࡾ❧ࡘࡇࡀ▱ࡽࢀ࡚࠸ࡿ[24, 25]㸬ࡑࡇ࡛ᅗ 4(b)ᤄධᅗ࣮࣍ࣝゅ ᑐࡍࡿࣉࣟࢵࢺࢆ♧ࡋࡓ㸬ࢥ࣮࣮ࣛ๎ᑐࡋ࡚ࡣࢫࢣ࣮ࣝࡉࢀ࡞࠸'Uxx(H)/Uxxࡀྠ୍⥺ୖࡾ, ࡇ ࡢ⣔࠾࠸࡚ಟṇࢥ࣮࣮ࣛ๎ࡀᡂࡾ❧ࡘࡇࡀ♧ࡉࢀࡿ㸬 ࡇࡇࡲ࡛♧ࡋࡓࡼ࠺㕲⣔㉸ఏᑟయ BaFe2(As1-xPx)2ࡣ, Uxx(T)ҏ, RH(T),ҏ ཬࡧ'Uxx(H)/Uxxࡢ࡚ࡢ㍺㏦⌧ ㇟࠾࠸࡚, ᚑ᮶ࡢࣇ࢙࣑ࣝᾮయⓗࡿ⯙࠸ࡽ㐓⬺ࡋࡓᣲືࢆ♧ࡍࡇࡀ᫂ࡽ࡞ࡗࡓ㸬ࡇࡢࡼ ࠺࡞㠀ࣇ࢙࣑ࣝᾮయⓗ㍺㏦⌧㇟ࡣ, 㖡㓟≀㉸ఏᑟయࡸ‽ḟඖ㔜࠸㟁Ꮚ⣔ྜ≀࡞࠸ࢃࡺࡿᙉ ☢ᛶ㏆ഐ࠶ࡿᙉ┦㛵㟁Ꮚ⣔࠾࠸࡚ඹ㏻ほ ࡉࢀ࡚࠸ࡿ≉ᚩ࡛࠶ࡿ[26,,27]㸬ࡇࢀࡀ㕲⣔㉸ఏᑟయ ࡢ᭱㐺⨨㏆ഐ࠾࠸࡚ࡶほ ࡉࢀࡓࡇࡣᴟࡵ࡚⯆῝࠸㸬ཪ, 㢮ఝࡢ⣔ࡋ࡚, ᅽຊୗ࠶ࡿ
CaFe2As2ࡸᏛⓗᅽຊࡢᑟධࡉࢀࡓ⣔࡛࠶ࡿ CaFe2(As1-xPx)2࡛ࡣ, collapsed tetragonal (cT)┦࠸࠺⤖ᬗ
(a) BaFe2As2(x=0) (b) BaFe2P2(x=1) (c) (d) (e) ᅗ 5. (a)BaFe2As2, (b)BaFe2AP2 ࡢࣇ࢙࣑ࣝ㠃(c)x=0, (d)x=0.3, (e)x=1.0ࡢ(110)᪉ྥࡢ᩿㠃ᅗ[9, 10]. ᑟࡀ㉳ࡇࡽࡎ, ୖグࡢ࡚ࡢ㍺㏦⌧㇟ ᐃ࡛㏻ᖖࡢࣇ࢙࣑ࣝᾮయⓗ≧ែࡀᐇ⌧ࡋ࡚࠸ࡿࡇࡀ᭱㏆ࡢ ◊✲ࡼࡗ࡚᫂ࡽ࡞ࡗ࡚࠸ࡿ[28]㸬ࡇࡢࡇࡽࡶ㕲⣔㉸ఏᑟ㠀ࣇ࢙࣑ࣝᾮయⓗ㍺㏦⌧㇟ࢆࡶ ࡓࡽࡍࡼ࠺࡞㠀ᚑ᮶ᆺࡢᩓᶵᵓࡢ㛫ࡣ, ᙉ࠸┦㛵ࡀᏑᅾࡋ࡚࠸ࡿࡇࡀ᫂ࡽ࡛࠶ࡿ㸬㔜࠸㟁Ꮚ ⣔ࡸ㖡㓟≀㧗 ㉸ఏᑟయ࡛ࡣ, ࡇࡢࡼ࠺࡞㠀ࣇ࢙࣑ࣝᾮయⓗ㍺㏦⌧㇟ࡢ㉳※ࡋ࡚, ‽⢏Ꮚࡀ≉ᐃ ࡢἼᩘࡢᙉ☢ᛶᦂࡽࡂࡼࡗ࡚ᙉࡃᩓࡉࢀࡿࡇࡼࡾ, ࣂࢵࢡࣇ࣮ࣟ࠸࠺⦆㛫㏆ఝ࠾ ࡅࡿ㟁ὶ㡯ࡢ⿵ṇࡀ⏕ࡌ, ࡇࢀࡼࡗ࡚ከࡃࡀㄝ᫂ྍ⬟࡛࠶ࡿࡢ㆟ㄽࡀ࡞ࡉࢀ࡚࠸ࡿ[24,27]㸬ࡇ ࢀࡽࡢ⣔ྠࡌࡃᙉ☢ᛶ㏆ഐ⨨ࡍࡿ㕲⣔㉸ఏᑟయ࠾࠸࡚, ࡇࡢࡼ࠺࡞ຠᯝࡀࡢࡼ࠺ྲྀࡾ ධࢀࡽࢀ࡚ࡃࡿ, ᚋࡢ◊✲ࡀᚅࡓࢀࡿࡇࢁ࡛࠶ࢁ࠺㸬 㸬G+Y$ ື㔞Ꮚ⮫⏺Ⅼⓗࡿ⯙࠸ ౯ᩘ᧯సࡼࡿ࢟ࣕࣜࢻ࣮ࣉࢆకࢃࡎᇶᗏ≧ែࡀኚྍ⬟࡞ BaFe2(As1-xPx)2࡛ࡣ, ⤖ᬗᵓ㐀ࡢ ኚ, ࡇࢀక࠺ࣇ࢙࣑ࣝ㠃ࡢࢺ࣏ࣟࢪ࣮ࡢኚࡀ㔜せ࡞ᙺࢆᯝࡓࡋ࡚࠸ࡿ⪃࠼ࡽࢀࡿ㸬ᅗ
5(a)-(b)ࡣ࢚ࣥࢻ≀㉁࡛࠶ࡿ BaFe2As2ཬࡧ BaFe2P2ࡘ࠸࡚, LDA ࣂࣥࢻィ⟬ࡼࡾᚓࡽࢀࡓࣇ࢙࣑ࣝ
㠃ࡢᅗ࡛࠶ࡿ㸬୧࢚ࣥࢻࡣࡕࡽࡶ 2 ᯛࡢ㟁Ꮚ㠃ࢆᣢࡘࡀ, BaFe2As2ࡣḟඖⓗ࡞ 3 ᯛࡢ࣮࣍ࣝ㠃ࢆᣢ ࡕ, ୍᪉ BaFe2P2ࡣ࣮࣍ࣝ㠃ࡀ 2 ᯛ࡛࠺ࡕ 1 ᯛࡀᙉ࠸୕ḟඖᛶࢆᣢࡘⅬࡀ␗࡞ࡿ㸬ࢫࣆࣥᦂࡽࡂᶵᵓࡢ ❧ሙࡓࡗ࡚༢⣧࡞ゎ㔘ࢆࡍࡿ࡞ࡽࡤ, P⨨క࠸ᅗ5(c)-(e)ࡢࡼ࠺࣮࣍ࣝ㠃୕ḟඖᛶࡀ⌧ࢀ, ࢿ ࢫࢸࣥࢢ᮲௳ࡀᝏࡍࡿࡇ࡛ SDW ┦㌿⛣ࡀᢚไࡉࢀ㉸ఏᑟࡀㄏ㉳ࡉࢀࡿ⪃࠼ࡿࡇࡀ࡛ࡁࡿ㸬 ࡉ࡚, ࣂࣥࢻィ⟬ࡽண ࡉࢀࡿ㟁Ꮚ≧ ែᑐࡋ, ᐇ㝿ࡢ⣔ࡀࡢࡼ࠺࡞ࡗ࡚࠸ ࡿࢆᐇ㦂ⓗ᫂ࡽࡋ, ࡑࡢᕪ␗ࢆㄪ ࡿࡇ࡛㟁Ꮚࡢከయຠᯝ㛵ࡍࡿ㔜せ࡞ ሗࢆᚓࡿࡇࡀฟ᮶ࡿ㸬ࡇࡢࡼ࠺࡞ࣇ࢙ ࣑ࣝ㠃ࡢሗࢆᚓࡿᡭẁࡢ୍ࡘ㔞Ꮚື ࡢほ ࡀ࠶ࡿ㸬➹⪅ࡽࡣ BaFe2(As1-xPx)2ࡘ ࠸࡚࣐ࢡࣟ࢝ࣥࢳࣞࣂ࣮ࢆ⏝࠸ࡓ㧗☢ሙ ☢Ẽࢺࣝࢡ ᐃࢆ⾜࠸, x = 0.41̺1 ࠸࠺ ᐇᗈ࠸⨨⠊ᅖ㸦TcӘ 0.8TcMax㸧࠾࠸࡚, ࢻࣁ࣮ࢫ࣭ࣇ࣭ࣥࣝࣇ࢙ࣥ(dHvA)ື ࢆほ ࡍࡿࡇᡂຌࡋࡓ[10]㸬 ᅗ 6(a)ࡣࣇ࣮࢚ࣜኚࡉࢀࡓ☢Ẽࢺࣝࢡࡢືࢫ࣌ࢡࢺ࡛ࣝ࠶ࡿ㸬dHvA ࿘Ἴᩘ F ࡣ, ࢜ࣥࢧ࣮࣮࢞ ࡢ㛵ಀᘧ F = (/2Se)Akࡼࡗ࡚ࣇ࢙࣑ࣝ㠃ࡢᴟ್᩿㠃✚ Akࢆ࠼ࡿ㸬ཪ, dHvA ືࡢᖜࡽࡣ, ࣜ ࣇࢩࢵࢶ-ࢥࢭࣅࢵࢳࡢᘧࡼࡾ‽⢏Ꮚࡢ᭷ຠ㉁㔞ࡀ⟬ฟࡉࢀࡿ[29]㸬ᐇ㦂࡛ࡣ 2 ࡘࡢ dHvA ࿘Ἴᩘࡀ ほ ࡉࢀࡓ㸬ࡑࡢ☢ሙ᪉ྥ౫Ꮡᛶࡣ, ḟඖࣇ࢙࣑ࣝ㠃ᑐࡋ࡚ᮇᚅࡉࢀࡿ F ~ 1/cosT Tࡣ c ㍈ࡽ ☢ሙ༳ຍゅᗘࡾ, ࣂࣥࢻィ⟬ࡽண ࡉࢀࡿ 2 ࡘࡢ㟁Ꮚ㠃ࢆほ ࡋ࡚࠸ࡿࢧࣥࡉࢀࡿ㸬ࡋ ࡋ࡞ࡀࡽ, ࣂࣥࢻィ⟬࡛ࡣ㟁Ꮚ㠃ࡢᴟ್᩿㠃✚ࡀ, x ࡰ౫Ꮡࡋ࡞࠸ண ࡉࢀࡿࡢᑐࡋ, ᐇ㦂 ⤖ᯝࡣࡁࡃ␗࡞ࡾ, x ࡀᑠࡉࡃ࡞ࡿඹᴟ್᩿㠃✚ࡀ㐃⥆ⓗῶᑡࡋ࡚࠸ࡿ㸬ྠ, ᐇ㦂ࡽồ ࡵࡽࢀࡿ‽⢏Ꮚࡢ᭷ຠ㉁㔞ࡶࣂࣥࢻィ⟬ࡢࡁ࡞ᕪ␗ࡀぢࡽࢀࡿ㸬ྛ x ࡢヨᩱࡘ࠸࡚᭷ຠ㉁㔞 ࢆぢ✚ࡶࡿ, ࣂࣥࢻィ⟬ࡽぢ✚ࡶࡽࢀࡿ㉁㔞 mbほ ࡉࢀࡓ᭷ຠ㉁㔞 m*ࡢẚࡣ x = 1 ࠾࠸࡚ m*/mb ~ 2࡛࠶ࡗࡓࡶࡢࡀ, x ࡢῶᑡࡶ㐃⥆ⓗࡁࡃ࡞ࡾ, x = 0.41 ࡛ࡣ m*/mb ~ 4࡞ࡿ(ᅗ 3)㸬 ࡇࡢࡼ࠺࡞ࣇ࢙࣑ࣝ㠃ࡢ⦰ᑠ᭷ຠ㉁㔞ࡢቑࡣ, ༢⣧࡞ LDA ィ⟬ࡁࡃ␗࡞ࡗ࡚࠾ࡾ, 㧗࠸ Tcࢆ
ᅗ 7. BaFe2(As1-xPx)2ྛ⤌ᡂヨᩱ࡛ࡢ31P-1/T1Tࡢ ᗘኚ [11]. 䢪䣣䢫 䢪䣤䢫 䢪䣥䢫 䢪䣦䢫 䢪䣧䢫 䢪䣨䢫 ᅗ 6. (a)☢Ẽࢺࣝࢡࡢࣇ࣮࢚ࣜࢫ࣌ࢡࢺࣝ㸬(b)BaFe2P2ࡢࣂࣥࢻィ⟬ࡽண ࡉࢀࡿ dHvA ࿘Ἴᩘ㸪ཬࡧ (c)-(f)x = 1.0 - 0.41࡛ほ ࡉࢀࡓ dHvA ࿘Ἴᩘࡢ☢ሙ᪉ྥ౫Ꮡᛶ[8]. ࡶࡘࡼ࠺࡞㕲⣔㉸ఏᑟయ࡛ࡣ, 㟁Ꮚ⣔ᑐࡍࡿከయຠᯝࡀ㔜せ࡛࠶ࡿࡇࢆ♧၀ࡋ࡚࠸ࡿ㸬ᑦ, dHvA ືࡽᑟࢀࡿ㟁Ꮚ≧ែྠࡌᥥീࡀ, ᭱㐺⨨ヨᩱᑐࡍࡿゅᗘศゎග㟁Ꮚศග ᐃࡽࡶᚓࡽ ࢀ࡚࠸ࡿ[14]㸬ࡇࡢࡼ࠺࡞᭷ຠ㉁㔞ࡢቑࡣ, 㠀ࣇ࢙࣑ࣝᾮయⓗ㍺㏦⌧㇟ࢆ♧ࡍ‽ḟඖ㔜࠸㟁Ꮚ⣔ࡢ ᙉ☢ᛶ㔞Ꮚ⮫⏺Ⅼ㏆ഐ࠾࠸࡚ࡶほ ࡉࢀ࡚࠸ࡿ[30]㸬 ᭱ᚋ, ᙉ☢ᛶᦂࡽࡂࡢࡁࡉࡢኚࡘ࠸࡚㏙ࡓ࠸㸬ࡇࢀ㛵ࡋ࡚ࡣ᰾☢Ẽඹ㬆(NMR) ᐃ ࡼࡾ, ᰾ࢫࣆࣥ-᱁Ꮚ⦆⋡ 1/T1ࢆ㏻ࡌ࡚ືⓗᖏ☢⋡ࡢప࢚ࢿࣝࢠ࣮ᡂศ㛵ࡍࡿሗࢆᚓࡿࡇࡀ ࡛ࡁࡿ㸬≉, BaFe2(As1-xPx)2ࡢሙྜ, ⤌ᡂࡼࡿ≧ែᐦᗘࡢኚࡀṤ࡞ࡃ, 1/T1Tࡽᙉ☢ᛶᦂࡽࡂ ࡢࡁࡉࡘ࠸࡚ࡢ᫂ᛌ࡞㆟ㄽࡀྍ⬟࡞ࡿ㸬ᐇ㦂⤖ᯝࡣ 1/T1T ࡀ㧗 ࡛⤌ᡂࡼࡽࡎࡰ୍ᐃ್ࢆ ♧ࡋ, ᭱㐺⨨㏆ഐ࡛ࡣప ྥࡗ࡚ࡁ ࡞ୖ᪼ࢆ♧ࡍ㸬ࡇࢀᑐࡋ࡚ x ࡀࡁࡃ࡞ࡾ Tcࡀపࡃ࡞ࡿ 1/T1T ࡢୖ᪼ࡀᢚ࠼ࡽࢀࡿ⤖ ᯝࡀᚓࡽࢀ࡚࠸ࡿ(ᅗ㸵)㸬ࡇࡢ⤖ᯝࢆ 1/T1T = a + b(T + T)-1࠸࠺ᘧ࡛ࣇࢵࢺࡍࡿࡇࡼ ࡾ, ☢Ẽᦂࡽࡂࡢࡁࡉࢆ≉ᚩࡅࡿ ᗘ T : ࣡ࢫ ᗘ ࡀồࡵࡽࢀ, ⯆῝࠸ࡇ, ᭱㐺⨨㏆ഐ࡛T § 0 ࡞ࡿࡇࡀ♧ࡉࢀࡿ (ᅗ 3)㸬ࡇࢀࡣ BaFe2(As1-xPx)2☢Ẽ㔞Ꮚ⮫⏺ Ⅼ(TÆ 0)ࡀᏑᅾࡍࡿࡇࢥࣥࢩࢫࢸࣥࢺ࡞ ᥥീࢆ࠼࡚࠸ࡿ[11]㸬 ௨ୖ♧ࡋࡓࡼ࠺㕲⣔㉸ఏᑟయ BaFe2(As1-xPx)2ࡣᵓ㐀/☢Ẽ┦㌿⛣ᾘኻࡢ┤㏆࡛, ᚑ᮶ࡢࣇ࢙࣑ࣝ ᾮయⓗ㍺㏦⌧㇟ࡣࡁࡃ␗࡞ࡿ㠀ࣇ࢙࣑ࣝᾮయⓗ࡞㍺㏦⌧㇟ࢆ♧ࡍ㸬ྠ, ࡇࡢࡼ࠺࡞㡿ᇦ࡛ࡣ ᭷ຠ㉁㔞ࡢቑࣇ࢙࣑ࣝ㠃ࡢ⦰ᑠ, ᙉ☢ᛶᦂࡽࡂࡢቑ, ࣡ࢫ ᗘࡢᾘኻࡀほ ࡉࢀ, ࡑࡇ࡛ ㉸ఏᑟࡣ᭱㧗ࡢ Tcࢆ♧ࡍ㸬ࡇࢀࡽࡣఱࢀࡶ㟁Ꮚ⣔ᑐࡍࡿྠࡌከయຠᯝ, ༶ࡕᙉ☢ᛶᦂࡽࡂࢆ㉳※ ࡍࡿᛮࢃࢀ, ᵓ㐀/☢Ẽ┦㌿⛣ࡢᾘኻⅬ㔞Ꮚ⮫⏺Ⅼࡀ࠶ࡿ⪃࠼ࡿᥥീࢥࣥࢩࢫࢸࣥࢺ࡛࠶ࡿ㸬 ࡇࡢ⣔ࡢ㉸ఏᑟᙉ☢ᛶᦂࡽࡂࡢ㛫ࡣᙉ࠸┦㛵㛵ಀࡀᏑᅾࡋ, 㟁Ꮚᑐᙧᡂࡀࢫࣆࣥᦂࡽࡂࡼ ࡿࡍࡿᶵᵓ▩┪ࡋ࡞࠸㸬ణࡋ, ᭱㏆, 㕲⣔㉸ఏᑟࡢูࡢ⌮ㄽࣔࢹࣝࡋ࡚, ୍᪉࡛, ᙅ࠸ shear ࣇ࢛ ࣀࣥࡀ㌶㐨ᦂࡽࡂࡢ⮫⏺ⓗ࡞ቑࢆࡶࡓࡽࡋ, ࡇࡢ㌶㐨ᦂࡽࡂࡀ➢ྕ㌿ࡢ࡞࠸ s++ Ἴ㉸ఏᑟࢆᐇ⌧
ࡋ࡚࠸ࡿࡢ࡛ࡣ࡞࠸ࡢᣦࡶ࡞ࡉࢀ࡚࠸ࡿ[31-34]㸬ࡇࡢࡼ࠺࡞㌶㐨ᦂࡽࡂࡼࡗ࡚ࡶ㠀ࣇ࢙࣑ࣝ ᾮయⓗ㍺㏦⌧㇟ࡀ⌧ࢀࡿࡢᣦࡀ࡞ࡉࢀ࡚࠾ࡾ, 㕲⣔㉸ఏᑟయࡢ㟁Ꮚᑐᙧᡂᶵᵓࢆ⌮ゎࡍࡿࡣ, ᚋ, ㉸ఏᑟ┦࿘㎶࡛ࡢ㌶㐨ࡺࡽࡂࡢᏑᅾࢆᐇ㦂ⓗ᫂ࡽࡋ, ࡑࢀࡀ࠺㉸ఏᑟ┦㛵ࡋ࡚࠸ࡿ ࢆ᫂☜ࡍࡿࡇࡀ୍ࡘࡢ㔜せ࡞㘽࡞ࡿࡔࢁ࠺㸬 㸬࠾ࢃࡾ ᮏ✏࡛ࡣ, 㕲⣔㉸ఏᑟయ BaFe2(As1-xPx)2ࢆࡋ࡚, ⣧Ⰻ༢⤖ᬗࡳࡿ㠀ࣇ࢙࣑ࣝᾮయⓗ࡞㍺㏦⌧㇟ 㔞Ꮚ⮫⏺Ⅼⓗ࡞ࡿ⯙࠸↔Ⅼࢆᙜ࡚࡚⤂ࢆࡋࡓ㸬ࡇࡢࡼ࠺࡞ࡿ⯙࠸ࡣ㖡㓟≀㉸ఏᑟయࡸ, ‽ḟඖ㔜࠸㟁Ꮚ⣔ྜ≀࡛ࡶほ ࡉࢀ࡚࠸ࡿ⌧㇟࡛࠶ࡾ, 㕲⣔㉸ఏᑟయ࡛ࡣࡇࢀࡽࡢ⣔ࡢඹ㏻࡞ ␗ᖖࡀᵝࠎࡳࡽࢀࡿ㸬୍᪉, ᮏ✏࡛ࡣ⤂ࡋ࡞ࡗࡓࡀ, BaFe2(As1-xPx)2࡛ࡣࣇ࢙࣑ࣝ㠃ୖ㉸ఏᑟࢠࣕ ࢵࣉᵓ㐀ࡀ㛢ࡌࡓࣀ࣮ࢻ ⠇ ᵓ㐀ࢆᣢࡕ, 㕲⣔㉸ఏᑟయࡣ≀㉁ࡼࡗ࡚ࣀ࣮ࢲࣝࣀ࣮ࢻࣞࢫࡢ 2 ✀ 㢮ࡢ㉸ఏᑟࢠࣕࢵࣉᵓ㐀ࡀᐇ⌧ࡋ࡚࠸ࡿ࠸࠺, ࡇࢀࡲ࡛ࡢ㉸ఏᑟయ⣔ࡣ࡞࠸᪂ࡋ࠸ഃ㠃ࡀ᫂ࡽ ࡞ࡗ࡚࠸ࡿ[10,11,35-47]㸬➹⪅ࡽࡣ, 㕲⣔㉸ఏᑟࢆ⌮ゎࡍࡿࡓࡵࡣ㉸ఏᑟ┦࿘㎶࡛ࡢ␗ᖖ࡞ᖖఏᑟ ≧ែࡢ⌮ゎከᵝ࡞ࢠࣕࢵࣉᵓ㐀ࢆ࠼ࡿᅉᏊࡢⅬࢆ᫂ࡽࡍࡿࡇࡀ, ᚋࡢ◊✲ࡢ㘽࡞ࡿ ⪃࠼࡚࠸ࡿ㸬 ㅰ㎡ ᮏ◊✲ࡣ, ᑎᔱᏕோ, ᯇ⏣♸ྖ, ⰪෆᏕ⚞, ᶫᮏ㢧୍㑻, ᒣୗ✨, ᡞᐶ᫂, ụ⏣ᾈ❶, ୰♸, ▼ ⏣᠇㸦ி㒔Ꮫ , A. Carrrington (Bristrol Univ.), A. Coldea (Oxford Univ.), ྜྷ⏣㕲ᖹ, ⸨᳃῟, ୗᚿ㈗ ༤, ㎞Ṫ ᮾிᏛ ࡢྛẶ, ཬࡧྛ◊✲ᐊࡢᏛ㝔⏕ࡢඹྠ◊✲ᇶ࡙ࡃࡶࡢ࡛ࡍ㸬ཪ, ๓㔝ᝋ㍤, ▮ᣢ⚽㉳, 㝜ᒣὒ ி㒔Ꮫ ࡢྛඛ⏕᪉ࡣᐇ㦂㠃࡛ࡢከࡃࡢࢧ࣏࣮ࢺࢆ㈷ࡗ࡚࠾ࡾࡲࡍ㸬⤃㇂ᾈ ྡ , 㯮ᮌᙪ 㟁㏻ ࡢ୧ඛ⏕ࡣ㈗㔜࡞ࡈ㆟ㄽࢆከࠎࡋ࡚㡬ࡁࡲࡋࡓ㸬ᮏ◊✲ࡣ㸪ప ≀㉁⛉Ꮫ◊ ✲ࢭࣥࢱ࣮ࡢඹྠ⏝ᶵჾ࡛࠶ࡿࢢ࣮ࣟࣈ࣎ࢵࢡࢫࡸ X ⥺ᅇᢡ⨨㸪ࡑࡋ࡚Ᏻᐃࡘከ㔞ࡢᐮ౪⤥ ࡢᚚᑾຊࡢୖᡂࡾ❧ࡗ࡚࠾ࡾࡲࡍ㸬ࡇࡇ῝ࡃឤㅰࢆ⮴ࡋࡲࡍ㸬 ཧ⪃ᩥ⊩
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