First-order quantum breakdown of superconductivity in amorphous superconductors
Thibault Charpentier, David Perconte, Sébastien Léger, Kazi Rafsanjani Amin, Florent Blondelle, Frédéric Gay, Olivier Buisson, Lev Ioffe, Anton Khvalyuk, Igor P… 展开作者
Thibault Charpentier, David Perconte, Sébastien Léger, Kazi Rafsanjani Amin, Florent Blondelle, Frédéric Gay, Olivier Buisson, Lev Ioffe, Anton Khvalyuk, Igor Poboiko, Mikhail Feigel'man, Nicolas Roch, Benjamin Sacépé
本文通过微波谐振器测量证明氧化铟非晶超导薄膜在临界无序处发生一阶量子相变，揭示超流刚度和转变温度的跳变及 Cooper 对排斥相互作用的关键作用。
摘要：
连续量子相变被广泛假定并在各种量子粒子或自旋系统中频繁观察到。其特征涉及标度律，即在接近量子临界点时，序参量以二阶方式被逐渐抑制。无序超导体中 Cooper 对的局域化以及由此导致的 superconductivity 击穿长期以来一直是一个典型例子。在此，我们展示了偏离这一范式的现象，证明氧化铟非晶超导薄膜经历了一种由无序调控的独特、不连续的一阶量子相变。通过系统测量超导微波谐振器中的等离激元谱，我们提供了证据，表明在临界无序处，零温超流刚度和转变温度都出现了显著跳变。这种不连续转变揭示了此前被忽视的 Cooper 对之间排斥相互作用的作用，以及随后 superconductivity 与绝缘 Cooper 对玻璃之间竞争的重要性。此外，我们的研究表明，薄膜的临界温度不再与配对振幅相关，而是与超流刚度一致，这与预形成 Cooper 对的赝能隙区域相符。我们的发现为无序在量子相变中的作用提出了根本性的新问题，并对量子电路中的超电感具有启示意义。
英文摘要：
Continuous quantum phase transitions are widely assumed and frequently observed in various systems of quantum particles or spins. Their characteristic trait involves scaling laws governing a second-order, gradual suppression of the order parameter as the quantum critical point is approached. The localization of Cooper pairs in disordered superconductors and the resulting breakdown of superconductivity have long stood as a prototypical example. Here, we show a departure from this paradigm, showcasing that amorphous superconducting films of indium oxide undergo a distinctive, discontinuous first-order quantum phase transition tuned by disorder. Through systematic measurements of the plasmon spectrum in superconducting microwave resonators, we provide evidence for a marked jump of both the zero-temperature superfluid stiffness and the transition temperature at the critical disorder. This discontinuous transition sheds light on the previously overlooked role of repulsive interactions between Cooper pairs and the subsequent competition between superconductivity and insulating Cooper-pair glass. Furthermore, our investigation shows that the critical temperature of the films no longer relates to the pairing amplitude but aligns with the superfluid stiffness, consistent with the pseudogap regime of preformed Cooper pairs. Our findings raise fundamental new questions into the role of disorder in quantum phase transitions and carry implications for superinductances in quantum circuits.
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