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arXiv 1504.01360cond-mat.supr-concond-mat.mtrl-sci
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CuxBi2Se3超导电性对淬灭条件的依赖性

Dependence of superconductivity in CuxBi2Se3 on quenching conditions

J. A. Schneeloch, R. D. Zhong, Z. J. Xu, G. D. Gu, J. M. Tranquada

摘要:

拓扑超导性,意味着无间隙保护的表面状态,最近被提出存在于化合物CuxBi2Se3。不幸的是,低抗磁屏蔽分数和相当大的不均匀性已在该化合物中报道。为了理解和改进有限超导体积分数,我们研究了各种生长和退火条件的影响。与熔体生长(MG)的方法,抗磁屏蔽分数高达56%的Cu0.3Bi2Se3已获得,最高值报告这种方法。我们研究了各种淬火和退火条件的有效性,发现从560 ℃以上的温度淬火是超导性所必需的,而从较低的温度淬火或根本不淬火是有害的。一种改进的浮区法(FZ)产生了大的单晶,但超导性很小。即使在退火和淬火后,FZ生长的样品比MG生长的样品更少的机会超导。从低屏蔽分数在FZ生长的样品和淬火的依赖性,我们建议,亚稳的第二相具有小的体积分数在大多数样品中可能是负责的超导性。

英文摘要:

Topological superconductivity, implying gapless protected surface states, has recently been proposed to exist in the compound CuxBi2Se3. Unfortunately, low diamagnetic shielding fractions and considerable inhomogeneity have been reported in this compound. In an attempt to understand and improve on the finite superconducting volume fractions, we have investigated the effects of various growth and post-annealing conditions. With a melt-growth (MG) method, diamagnetic shielding fractions of up to 56% in Cu0.3Bi2Se3 have been obtained, the highest value reported for this method. We investigate the efficacy of various quenching and annealing conditions, finding that quenching from temperatures above 560C is essential for superconductivity, whereas quenching from lower temperatures or not quenching at all is detrimental. A modified floating zone (FZ) method yielded large single crystals but little superconductivity. Even after annealing and quenching, FZ-grown samples had much less chance of being superconducting than MG-grown samples. From the low shielding fractions in FZ-grown samples and the quenching dependence, we suggest that a metastable secondary phase having a small volume fraction in most of the samples may be responsible for the superconductivity.

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