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arXiv 1209.6464cond-mat.supr-concond-mat.mtrl-scicond-mat.str-el
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超导LaTiO3/SrTiO3界面的多量子相变

Multiple Quantum Phase Transitions at the superconducting LaTiO3/SrTiO3 interface

J. Biscaras, N. Bergeal, S. Hurand, C. Feuillet-Palma, A. Rastogi, R. C. Budhani, M. Grilli, S. Caprara, J. Lesueur

摘要:

研究了静电门控超导LaTiO_3/SrTiO_3界面的磁场驱动量子相变(QPT)。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。该系统可以被描述为一个无序阵列的超导岛耦合的二维电子气(2DEG)。根据由栅极电压调谐的2DEG电导,QPT是单的(对应于整个阵列中的长程相位相干性)或双的(一个与局部相位相干性相关,另一个与阵列相关)。通过计算相干长度临界指数ν,我们发现根据Harris准则,QPT可以是“干净的”或“脏的”,这取决于相位相干长度是小于还是大于岛的尺寸. Spivak等人的理论方法很好地描述了整体行为,在二维超导QPT的费米场景的框架中。

英文摘要:

We study the magnetic field driven Quantum Phase Transition (QPT) in electrostatically gated superconducting LaTiO3/SrTiO3 interfaces. Through 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 islands coupled by a two dimensional electron gas (2DEG). Depending on the 2DEG conductance tuned by the gate voltage, the QPT 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). By retrieving the coherence length critical exponent ν, we show that the QPT can be "clean" or "dirty" according to the Harris criteria, depending on whether the phase coherence length is smaller or larger than the island size. The overall behaviour is well described by a theoretical approach of Spivak et al., in the framework of the fermionic scenario of 2D superconducting QPT.

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