Multiple quantum criticality in a two-dimensional superconductor
Multiple quantum criticality in a two-dimensional superconductor
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DOI：
10.1038/nmat3624
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发表时间：
2013-06-01
期刊：
影响因子：
41.2
通讯作者：
Lesueur, J.
中科院分区：
文献类型：
--
作者：
Biscaras, J.;Bergeal, N.;Lesueur, J.
与发生在氧化物界面的二维电子气(2DEG)相关的各种现象包括特殊的载流子迁移率、磁性和超导电性等。虽然这些主要是未来潜在应用的兴趣焦点，但它们也为研究更基本的量子多体效应提供了机会。在这里，我们研究了发生在静电门控超导LaTiO_3/SrTiO_3界面上的磁场驱动的量子相变。通过有限尺寸标度分析，我们证明它属于(2+1)D XY模型普适类。该系统可以描述为一个由二维电导耦合的超导水坑的无序阵列，根据其电导，观察到的临界行为是单一的(对应于整个阵列中的长程相干性)或双重的(一个与局部相干性有关，另一个与阵列有关)。建立了临界场与二维电导关系的相图，并与理论结果相吻合。此外，通过恢复相干长度临界指数nu，我们发现根据Harris判据，量子临界行为可以是干净的或肮脏的，这取决于相干性长度是小于还是大于水坑的大小。
The diverse phenomena associated with the two-dimensional electron gas (2DEG) that occurs at oxide interfaces include, among others, exceptional carrier mobilities, magnetism and superconductivity. Although these have mostly been the focus of interest for potential future applications, they also offer an opportunity for studying more fundamental quantum many-body effects. Here, we examine the magnetic-field-driven quantum phase transition that occurs in electrostatically gated superconducting LaTiO3/SrTiO3 interfaces. Through a finite-size scaling analysis, we show that it belongs to the (2 + 1)D XY model universality class. The system can be described as a disordered array of superconducting puddles coupled by a 2DEG and, depending on its conductance, the observed critical behaviour is single (corresponding to the long-range phase coherence in the whole array) or double (one related to local phase coherence, the other one to the array). A phase diagram illustrating the dependence of the critical field on the 2DEG conductance is constructed, and shown to agree with theoretical proposals. Moreover, by retrieving the coherence-length critical exponent nu, we show that the quantum critical behaviour can be clean or dirty according to the Harris criterion, depending on whether the phase-coherence length is smaller or larger than the size of the puddles.