退火对轻掺杂$HoBa_2Cu_3O_{7-δ}$单晶涨落电导率和赝能隙的影响
Effects of annealing on the fluctuation conductivity and pseudogap in slightly doped $HoBa_2Cu_3O_{7-δ}$ single crystals
摘要：
研究了室温退火对乏氧$ReBa_2Cu_3O_{7-δ}$（Re = Ho）单晶ab基面涨落电导（FLC）$σ^\prime(T)$和赝能隙（PG）$Δ^*(T)$的影响。结果表明，在所有阶段的退火，FLC附近的$T_c$可以描述的Aslamazov $-$拉金和Maki $-$汤普森波动理论，证明了一个三维$-$二维交叉与温度的增加。交叉温度$T_0$用于确定沿$c$轴的相干长度，$ξ_c(0)$ =2.82在退火的中间阶段，揭示了二维FLC的异常增加，这与$HoBa_2Cu_3O_{7-δ}$（HoBCO）中未补偿磁矩的影响有关：$μ_{eff, Ho}$ =9.7 $μ_{B}$。对于淬火的样品S1，PG的温度依赖性具有典型的具有大量缺陷的单晶的形状。然而，$Δ^*(T)$在高温下具有两个小的额外最大值，这是具有明显孪晶的HoBCO单晶的特征，并指示样品的两相性质。在退火时，$Δ^*(T)$的形状显著改变，很可能是由于磁相互作用的增加（样品S2）。更重要的是数据在高温下的斜率变化，它变得大约3.5倍陡。由于退火过程中的扩散过程中的氧分布的有序性在一定程度上补偿了磁相互作用的影响。有趣的是，斜率原来是相同的FeAs为基础的超导体，这表明在PG状态的HoBCO中存在自旋密度波的可能性。
英文摘要：
The effect of annealing at room temperature on the fluctuation conductivity (FLC) $σ^\prime(T)$ and pseudogap (PG) $Δ^*(T)$ in the basal ab plane of $ReBa_2Cu_3O_{7-δ}$ (Re = Ho) single crystals with a lack of oxygen has been studied. It is shown that at all stages of annealing, the FLC near $T_c$ can be described by the Aslamazov$-$Larkin and Maki$-$Thompson fluctuation theories, demonstrating a 3D$-$2D crossover with increasing temperature. The crossover temperature $T_0$ was used to determine the coherence length along the $c$-axis, $ξ_c(0)$=2.82 A. At the inter-mediate stage of annealing, an anomalous increase in 2D FLC was revealed, which is associated with the influence of uncompensated magnetic moments in $HoBa_2Cu_3O_{7-δ}$ (HoBCO): $μ_{eff, Ho}$=9.7$μ_{B}$. For the quenched sample S1, the temperature dependence of the PG has a shape typical of single crystals with a large number of defects. However, $Δ^*(T)$ has two small additional maxima at high temperature, which is a feature of HoBCO single crystals with pronounced twins and indicates the two-phase nature of the sample. Upon annealing, the shape of $Δ^*(T)$ noticeably changes, very likely due to an increase in the magnetic interaction (sample S2). More important is the change in the slope of the data at high temperatures, which has become about 3.5 times steeper. The ordering of the oxygen distribution due to the diffusion process during annealing somewhat compensates for the influence of magnetic interaction. Interestingly, the slope turns out to be the same as for FeAs-based superconductors, suggesting the possibility of the existence of spin density waves in HoBCO in the PG state.
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