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arXiv 1802.09441cond-mat.supr-concond-mat.str-el
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多层带超导体中轨道量子化效应与Fulde-Ferrell-Larkin-Ovchinnikov不稳定性的相互作用

Interplay between orbital-quantization effects and the Fulde-Ferrell-Larkin-Ovchinnikov instability in multiple-band layered superconductors

Kok Wee Song, Alexei E. Koshelev

摘要:

本文研究了具有深带和浅带的双层超导体在垂直于超导层的磁场中的超导不稳定性。在浅带,准经典近似是不适用的,朗道量子化必须准确地解释。该带在磁场中的电子能谱由一维朗道能级微带组成。随着磁场的增加,当化学势进入和离开微带时,系统经历了一系列的Lifshitz跃迁。这些转变深刻地影响在低温下的上临界场的形状。此外,塞曼自旋分裂可能导致超导序参量的层间调制的非均匀态(Fulde-Ferrell-Larkin-Ovchinnikov态)。典型地,浅带中的量子化效应强烈地促进该态的形成。只有在自旋分裂能与朗道能级间距完全匹配的特殊共振情况下,均匀态才是有利的。此外,对于电子光谱参数之间的特定关系,可以实现交替的FFLO状态,其中序参量在相邻层之间改变符号。对于上述情况,如果浅带对库珀对有显著贡献,则在低温下可以产生重入高场超导态。

英文摘要:

We explore superconducting instability for a clean two-band layered superconductor with deep and shallow bands in the magnetic field applied perpendicular to the layers. In the shallow band, the quasiclassical approximation is not applicable, and Landau quantization has to be accounted for exactly. The electronic spectrum of this band in the magnetic field is composed of the one-dimensional Landau-level minibands. With increasing magnetic field the system experiences series of Lifshitz transitions when the chemical potential enters and exits the minibands. These transitions profoundly influence the shape of the upper critical field at low temperatures. In addition, the Zeeman spin splitting may cause the nonuniform state with interlayer modulation of the superconducting order parameter (Fulde-Ferrell-Larkin-Ovchinnikov state). Typically, the quantization effects in the shallow band strongly promote the formation of this state. The uniform state remains favorable only in the exceptional resonance cases when the spin-splitting energy exactly matches the Landau-level spacing. Furthermore, for specific relations between electronic spectrum parameters, the alternating FFLO state may realize, in which the order parameter changes sign between the neighboring layers. For all above cases, the reentrant high-field superconducting states may emerge at low temperatures if the shallow band has significant contribution to the Cooper pairing.

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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