An Inquiry into Two Intriguing Values of the Critical Current Density of Bi-2212

G. P. Malik, V. S. Varma
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Abstract

The empirically reported values of the critical current density (jc) of Bi-2212 as 2.4 × 105 (jc1; Sample 1) and 1.0 × 106 A/cm2 (jc2; Sample 2) are intriguing because both of them correspond to the same values of the temperature T = 4.2 K and the applied magnetic field H = 12 × 104 G. This difference is conventionally attributed to such factors—not all of which are quantifiable—as the geometry, dimensions and the nature of dopants and the manners of preparation of the samples which cause their granular structures, grain boundaries, alignment of the grains and so on to differ. Based on the premise that the chemical potential μ subsumes most of these features, given herein is a novel explanation of the said results in terms of the values of μ of the two samples. This paper revisits the problem that was originally addressed in [Malik G.P., Varma V.S. (2020) WJCMP, 10, 53-70] in the more accurate framework of a subsequent paper [Malik G.P., Varma V.S. (2021) JSNM, 34, 1551-1561]. Besides, it distinguishes between the contributions of the electro-electron (e-e) and the hole-hole (h-h) pairs to jc—a feature to which no heed was paid earlier. The essence of our findings is that the jcs of the two samples differ because they are characterized by different values of the primary variables μi and , where is the effective mass of a charge-carrier and me is the free-electron mass and i = 1 and 2 denote Sample 1 and Sample 2, respectively. In the scenario of the charge-carriers being predominantly h-h pairs, the values of these parameters are estimated to be: μ1 ≈ 12.3 meV, η1 ≈ 0.58; μ2 ≈ 22.7 meV, η2 ≈ 0.94. Following from these and similar estimates when the charge-carriers are e-e pairs, given below for each sample are the detailed results for the values of the secondary variables viz. the number density of the charge-carriers and their critical velocity, the number of occupied Landau levels and the magnetic interaction parameter.
Bi-2212临界电流密度两个有趣值的探讨
经验报道Bi-2212的临界电流密度(jc)为2.4 × 105 (jc1;样品1)和1.0 × 106 A/cm2 (jc2;样品2)很有趣,因为它们都对应于温度T = 4.2 K和外加磁场H = 12 × 104 g的相同值。这种差异通常归因于这些因素(并非所有这些因素都是可量化的),如掺杂剂的几何形状、尺寸和性质以及样品的制备方式,这些因素导致它们的颗粒结构、晶界、晶粒排列等不同。基于化学势μ包含了这些特征的前提,本文给出了用两个样品的μ值来解释上述结果的一种新方法。本文在后续论文[Malik g.p., Varma V.S. (2021) JSNM, 34, 1551-1561]的更准确框架下,重新审视了[Malik g.p., Varma V.S. (2020) WJCMP, 10,53 -70]中最初解决的问题。此外,它区分了电子-电子(e-e)和空穴-空穴(h-h)对jc的贡献,这是以前没有注意到的特征。我们发现的本质是两个样品的jcs不同,因为它们的主要变量μi和的值不同,其中为载流子的有效质量,me为自由电子质量,i = 1和2分别表示样品1和样品2。在载流子以h-h对为主的情况下,这些参数的值估计为:μ1≈12.3 meV, η1≈0.58;μ2≈22.7 meV, η2≈0.94。根据这些和类似的估计,当载流子是e-e对时,下面给出每个样品的次级变量值的详细结果,即载流子的数量密度及其临界速度,占据朗道能级的数量和磁相互作用参数。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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