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arXiv 0810.0241cond-mat.supr-concond-mat.str-el
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Hydrostatic pressure研究(Ba1-xKx)Fe2As2(x = 0和0.45)和CaFe2As2单晶的结构相变和超导电性

Hydrostatic pressure study of the structural phase transitions and superconductivity in single crystals of (Ba1-xKx)Fe2As2 (x = 0 and 0.45) and CaFe2As2

M. S. Torikachvili, S. L. Budko, Ni Ni, P. C. Canfield

摘要:

通过在1.8 - 300 K温度范围内、压力高达20 kbar和磁场高达9 T的条件下测量电阻率,研究了静水压力(P)对三元和赝三元铁砷化物CaFe_2As_2、BaFe_2As_2和(Ba_(0.55)K_(0.45))Fe_2As_2的结构相变和超导电性的影响。CaFe_2As_2和BaFe_2As_2(轻掺Sn)分别在170 K和85 K附近出现结构相变,在常压下不表现出超导性,而K掺杂的(Ba_(0.55)K_(0.45))Fe_2As_2在T < 30 K时表现出超导性。压力对BaFe_2As_2的影响是以约-1.04 K/kbar的速率将晶体学转变的起始温度向下移动,同时将整个ρ(T)曲线向下移动,而压力对超导(Ba_(0.55)K_(0.45))Fe_2As_2的影响是以约-0.21 K/kbar的速率将超导性的起始温度向更低的温度移动。压力对CaFe 2As 2的影响首先是抑制晶体学转变,并在12 K附近非常迅速地诱导超导性,即,P < 5 kbar。然而,更高的压力会带来另一种相变,其特征是电阻率降低,以及超导性的抑制,将超导性限制在以5 kbar附近为中心的狭窄压力圆顶内。讨论了(Ba_(0.55)K_(0.45))Fe_2As_2和CaFe_2As_2的上临界场(Hc_2)数据。

英文摘要:

We studied the effect of hydrostatic pressure (P) on the structural phase transitions and superconductivity in the ternary and pseudo-ternary iron arsenides CaFe2As2, BaFe2As2, and (Ba0.55K0.45)Fe2As2, by means of measurements of electrical resistivity (rho) in the 1.8 - 300 K temperature (T) range, pressures up to 20 kbar, and magnetic fields up to 9 T. CaFe2As2 and BaFe2As2 (lightly doped with Sn) display structural phase transitions near 170 K and 85 K, respectively, and do not exhibit superconductivity in ambient pressure, while K-doped (Ba0.55K0.45)Fe2As2 is superconducting for T < 30 K. The effect of pressure on BaFe2As2 is to shift the onset of the crystallographic transformation down in temperature at the rate of about -1.04 K/kbar, while shifting the whole rho(T) curves downward, whereas its effect on superconducting (Ba0.55K0.45)Fe2As2 is to shift the onset of superconductivity to lower temperatures at the rate of about -0.21 K/kbar. The effect of pressure on CaFe2As2 is first to suppress the crystallographic transformation and induce superconductivity with onset near 12 K very rapidly, i.e., for P < 5 kbar. However, higher pressures bring about another phase transformation characterized by reduced resistivity, and the suppression of superconductivity, confining superconductivity to a narrow pressure dome centered near 5 kbar. Upper critical field (Hc2) data in (Ba0.55K0.45)Fe2As2 and CaFe2As2 are discussed.

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