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arXiv 2409.16804cond-mat.supr-concond-mat.quant-gas
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非常规准二维超导体的隧穿谱

Tunneling spectra of unconventional quasi-two-dimensional superconductors

L. Pisani, A. G. Moshe, P. Pieri, G. Calvanese Strinati, G. Deutscher

AI总结:

本文研究了准二维低载流子密度超导体的隧穿谱,发现其强耦合及临界温度Tc处电导异常行为与考虑配对涨落效应的隧穿理论定量吻合,指出强耦合是该类超导体的普遍性质。

摘要:

超流凝聚从根本上可以不同于Bardeen-Cooper-Schrieffer (BCS)理论所预测的情况。在一大类低载流子密度超导体中,例如颗粒铝、掺杂氮化物和高Tc铜氧化物,隧穿实验揭示了强耦合而非弱耦合,以及电导在接近临界温度Tc时并未恢复到正常态的值。在此,我们表明这种行为与一种隧穿理论定量吻合,该理论考虑了在从弱耦合BCS到强耦合Bose-Einstein凝聚的交叉区域中出现的大配对涨落效应,前提是使用相干能量标度而非单粒子能隙来评估耦合比。我们还提出,倾向于强耦合是准二维低载流子密度超导体的一个普遍性质。

英文摘要:

Superfluid condensation can fundamentally be different from that predicted by the Bardeen-Cooper-Schrieffer (BCS) theory. In a broad class of low-carrier-density superconductors, such as granular aluminum, doped nitrides, and high-Tc cuprates, tunneling experiments reveal strong rather than weak coupling, as well as a conductance that does not return to that of the normal state upon approaching the critical temperature Tc. Here, we show that this behavior is in quantitative agreement with a tunneling theory that takes into account the large pairing-fluctuation effects that occur in the crossover region from weak-coupling BCS to strong-coupling Bose-Einstein condensation, provided the coherence energy scale rather than the single-particle energy gap is used to evaluate the coupling ratio. We also propose that the tendency toward strong coupling is a generic property of quasi-2D low-carrier-density superconductors.

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