Inducing Superconductivity by a Picosecond Pressure Transient in the Quasi-Two-Dimensional Organic Salt

自近100年前超导电性被发现以来，无数的研究集中在这一现象的起源和驱动机制上。特别是高温(高温)超导体的发展在过去已经引起了很大的关注，因为例如，室温超导体的发现将给电子工程带来革命性的变化。然而，尽管有这些努力，非常规超导电性的基本过程仍然不被理解。高温超导的原型材料是BEDT-TTF家族的准二维有机化合物。特别是，κ-(BEDT-TTf)2Cu[N(CN)2]Cl显示了非常丰富的相图，其中包括13K以下的压力驱动反铁磁绝缘-超导(AF-SC)相变。到目前为止，所有关于有机超导体的研究都集中在这些材料的平衡性质上，即系统对环境缓慢绝热变化的响应。相反，这项工作旨在研究用飞秒激光脉冲激励皮秒压力瞬变(声波)后超导相的动态形成。对沉积在有机化合物顶部的缓冲层的辐射在材料中发出声脉冲。这种压力瞬变以音速穿过样品，预计会引起AF-SC相变。利用这种方法，可以在时间域中直接观察到超导相的产生，而且，方向选择实验可以深入了解反铁磁涨落对超导电性的作用。

Since the discovery of superconductivity almost 100 years ago, countless studies focused on the origin and driving mechanisms of this phenomenon. In particular the development of high-temperature (high-Tc) superconductors has reached much attention in the past, as the finding of a room-temperature superconductor would, for example, revolutionize electronic engineering. However, despite these efforts, the fundamental processes of unconventional superconductivity are still not understood.Prototype materials for high-Tc superconductivity are the quasi-two-dimensional organic compounds of the BEDT-TTF family. In particular, the κ-(BEDT-TTF)2Cu[N(CN)2]Cl exhibits a very rich phase diagram including a pressure-driven antiferromagnetic insulating-to-superconducting (AF-SC) phase transition below 13 K. So far, all studies of organic superconductors focused on the equilibrium properties of these materials, i.e. the system's response to slow adiabatic changes of the environment. In contrast, the proposed work aims at the investigation of the dynamic formation of the superconducting phase after excitation of a picosecond pressure transient (sound wave) using femtosecond laser pulses. Irradiation of a buffer layer deposited on top of the organic compound launches an acoustic pulse in the material. This pressure transient traverses through the sample at the speed of sound and is expected to induce the AF-SC phase transition. Using this approach, the generation of the superconducting phase could be observed directly in the time domain, and, furthermore, the direction-selective experiment may yield insight into the role of antiferromagnetic fluctuations for superconductivity.