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arXiv 1704.03365cond-mat.supr-con
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超导界面中电子配对与相位相干的竞争

Competition between electron pairing and phase coherence in superconducting interfaces

G. Singh, A. Jouan, L. Benfatto, F. Couedo, P. Kumar, A. Dogra, R. Budhani, S. Caprara, M. Grilli, E. Lesne, A. Barthelemy, M. Bibes, C. Feuillet-Palma, J. Lesueur, N. Bergeal

摘要:

二维超导体所表现出的奇异电子相的巨大多样性使物理学家面临新的挑战。这些包括最近发现的原子Ga薄膜中的量子Griffith奇异性、近似拓扑绝缘体中的拓扑相和过渡金属二硫属化物层中的非常规Ising配对。在LaAlO_3/SrTiO_3异质结中,门可调超导电子气被限制在两个绝缘氧化物之间的界面处的量子阱中。值得注意的是,这种气体同时具有磁性和强烈的Rashba自旋轨道耦合,是产生马约拉纳费米子的候选系统。然而,在整个掺杂范围内,超导性的起源和向正常态过渡的性质仍然难以捉摸。缺少这样的关键信息会阻碍利用这一杰出的系统进行未来的超导电子学和拓扑量子计算。在这里,我们表明,LaAlO_3/SrTiO_3的超导相图是由电子配对和相位相干之间的竞争控制。通过共振微波实验,我们测量了超流的刚度,并推断出带隙能作为载流子密度的函数。而一个很好的协议与Bardeen-Cooper-Schrieffer(BCS)理论观察到在高载流子掺杂,我们发现,抑制Tc在低掺杂的宏观相位相干性,而不是在标准BCS理论中的电子配对的损失控制。我们发现只有很小一部分的电子凝聚成超导态,并提出这对应于高能dxz/yz带的弱填充,更容易拥有超导性

英文摘要:

The large diversity of exotic electronic phases displayed by two-dimensional superconductors confronts physicists with new challenges. These include the recently discovered quantum Griffith singularity in atomic Ga films, topological phases in proximized topological insulators and unconventional Ising pairing in transition metal dichalcogenide layers. In LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides. Remarkably, the gas coexists with both magnetism and strong Rashba spin-orbit coupling and is a candidate system for the creation of Majorana fermions. However, both the origin of superconductivity and the nature of the transition to the normal state over the whole doping range remain elusive. Missing such crucial information impedes harnessing this outstanding system for future superconducting electronics and topological quantum computing. Here we show that the superconducting phase diagram of LaAlO3/SrTiO3 is controlled by the competition between electron pairing and phase coherence. Through resonant microwave experiments, we measure the superfluid stiffness and infer the gap energy as a function of carrier density. Whereas a good agreement with the Bardeen-Cooper-Schrieffer (BCS) theory is observed at high carrier doping, we find that the suppression of Tc at low doping is controlled by the loss of macroscopic phase coherence instead of electron pairing as in standard BCS theory. We find that only a very small fraction of the electrons condenses into the superconducting state and propose that this corresponds to the weak filling of a high-energy dxz/yz band, more apt to host superconductivity

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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