A Zero-loop Sagnac Interferometer for Probing Spontaneous Time Reversal Symmetry Breaking in Topological Superconductors

用于探测拓扑超导体自发时间反演对称性破缺的零环萨格纳克干涉仪

• 批准号: RTI-2021-00322
• 负责人: Ye, Ziliang
• 金额: $ 2.84万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Research Tools and Instruments
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=718832
• 关键词: Zero; loop; Sagnac; Interferometer; Probing

This proposal is for the purchase of equipment required to build a zero-loop Sagnac interferometer for probing Kerr rotation with a sub-µrad sensitivity and a µm spatial resolution. The biggest breakthrough in two-dimensional materials recently is inarguably the discovery of correlated phases and superconductivity in twisted bilayer graphene. In addition, the successful isolation of monolayer high-temperature (Tc) superconductors was just reported last year. Inspired by these developments, our theorist colleague, Marcel Franz, proposed a new theory predicting that the first high-Tc topological superconductor can emerge out of a twisted bilayer of d-wave superconductors. The theory predicts that when two monolayers of d-wave superconductors are stacked with a forty-five degree twist angle, a /2 phase difference arises in the superconducting order parameter between the two layers. As a result, the total superconducting order parameter acquires chiral symmetry and the high-Tc superconductor becomes a high-Tc topological superconductor with a topological gap. Here we propose to experimentally test this theory by fabricating twisted bilayers of a high-Tc superconductor, Bi2Sr2CaCu2O8+, and probing their topological superconducting phase with light. According to the theory, the time reversal symmetry will spontaneously break below the transition temperature, which will give rise to a Polar Kerr Effect. Since the topological gap is much smaller than the probe light's photon energy, the Kerr rotation angle is expected to fall below µrad. Therefore we plan to build a state-of-the-art Sagnac interferometer with an extreme sensitivity for Kerr rotation (tens of nrads). This instrument will allow us to demonstrate the first high-Tc topological superconductor, as well as resolve some open fundamental questions in the field. Our new approach to realizing topological superconductivity at high temperature might enable new opportunities for topological quantum computing in the future. In collaboration with colleagues, we will also apply the proposed equipment to probing the marginal time reversal symmetry breaking in other low-dimensional systems, such as the twisted bilayer graphene (Folk group), the MBE-grown monolayer ferromagnet, Fe3GeTe2 (Zou group), the surface state in HfNiSn along the (111) direction (Aronson group), high-entropy magnetic alloys (Hallas group), and transition-metal dichalcogenide heterostructures, which is of my own group's interest. The experience of working with the state-of-the-art Sagnac interferometer will provide our HQPs with extremely valuable skills which will help their careers both within and beyond academia.

该提案用于购买所需的设备，用于建立零环路Sagnac干涉仪，用于探测Kerr旋转，灵敏度为亚微弧度，空间分辨率为微米。最近在二维材料方面最大的突破无疑是在扭曲的双层石墨烯中发现了相关相和超导电性。此外，去年刚刚报道了成功分离单层高温(TC)超导体的报道。受这些发展的启发，我们的理论家同事Marcel Franz提出了一个新的理论，预测第一个高T_c拓扑超导体可以从d波超导体的扭曲双层中出现。该理论预测，当d波超导体的两个单分子层以45度的扭转角堆积时，两层之间的超导序参数会出现a/2的位相差。结果表明，总超导序参数具有手征对称性，高T_c超导体成为具有拓扑带隙的高T_c拓扑超导体。 在这里，我们建议通过制备高温超导体Bi2Sr2CaCu2O8+的扭曲双层膜，并用光探测它们的拓扑超导相来实验验证这一理论。根据该理论，时间反转对称性会自发地在相变温度以下破裂，从而产生极克尔效应。由于拓扑间隙比探测光的光子能量小得多，克尔旋转角预计将降至微rad以下。因此，我们计划建造一台最先进的Sagnac干涉仪，对克尔旋转(数十nrad)具有极高的灵敏度。这台仪器将使我们能够展示第一个高T_c拓扑超导体，并解决该领域一些悬而未决的基本问题。我们在高温下实现拓扑超导的新方法可能会为未来的拓扑量子计算提供新的机会。 与同事们合作，我们还将利用所提出的设备来探索其他低维系统中的边缘时间反对称破缺，如扭曲的双层石墨烯(Folk群)、分子束外延生长的单层铁磁体、Fe3GeTe2(邹群)、HfNiSn沿(111)方向的表面态(Aronson群)、高熵磁性合金(Hallas群)和过渡金属二卤化物异质结构，这是我所在团队的兴趣所在。使用最先进的Sagnac干涉仪的经验将为我们的HQP提供极其宝贵的技能，这将有助于他们在学术界内外的职业生涯。