从电子对形成实验看纳米尺度现象学
Nanoscale Phenomenology from Visualizing Pair Formation Experiment
摘要：
最近，Gomes等人[1]在高T_c超导体Bi_2Sr_2CaCu_2 O_{8+δ}中观察到了临界温度T_c以上纳米尺度区域（NR）的能隙形成。已经发现，随着温度的降低，NR在由不均匀性组成的体超导状态下膨胀。不均匀性[2]的尺寸接近NR [1]的最小尺寸的事实导致超导相是这些重叠NR的结果的结论。本文对NR的电荷和渗流态进行了分析，结果表明，在第一临界掺杂x_{c1}时，当超导开始时，每个NR都带有正的电荷（单位为电子电荷），因此我们将NR归结为一个空穴玻色子，并出现了连接这些玻色子的渗流线。在第二临界掺杂x_{c2}，当超导性消失时，我们的分析表明，每个NR的电荷等于2。x_{c2}的起源可以通过在NR中引入额外的正常相空穴费米子来理解，其出现在x_{c1}上方的浓度随着掺杂而平滑地增加，并且破坏了x_{c2}处玻色子的渗透线。最后一个导致赝隙（PG）区域的体玻色子性质消失，这解释了能斯特效应中涡旋存在的上限[3]。由于[1]已经证明了在PG边界处没有NR，我们可以得出结论，沿着这个边界，以及在x_{c2}中，所有的玻色子都消失了。
英文摘要：
Recently, Gomes et al. [1] have visualized the gap formation in nanoscale regions (NRs) above the critical temperature T_c in the high-T_c superconductor Bi_2Sr_2CaCu_2O_{8+δ}. It has been found that, as the temperature lowers, the NRs expand in the bulk superconducting state consisted of inhomogeneities. The fact that the size of the inhomogeneity [2] is close to the minimal size of the NR [1] leads to a conclusion that the superconducting phase is a result of these overlapped NRs. In the present paper we perform the charge and percolation regime analysis of NRs and show that at the first critical doping x_{c1}, when the superconductivity starts on, each NR carries the positive electric charge one in units of electron charge, thus we attribute the NR to a single hole boson, and the percolation lines connecting these bosons emerge. At the second critical doping x_{c2}, when the superconductivity disappears, our analysis demonstrates that the charge of each NR equals two. The origin of x_{c2} can be understood by introducing additional normal phase hole fermions in NRs, whose concentration appearing above x_{c1} increases smoothly with the doping and breaks the percolation lines of bosons at x_{c2}. The last one results in disappearing the bulk bosonic property of the pseudogap (PG) region, which explains the upper bound for existence of vortices in Nernst effect [3]. Since [1] has demonstrated the absence of NRs at the PG boundary one can conclude that along this boundary, as well as in x_{c2}, all bosons disappear.
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