近日，美国康奈尔大学的B.J.Ramshaw及其研究团队取得一项新进展。经过不懈努力，他们揭示常温下UTe2中的单组分超导性。相关研究成果已于2024年5月9日在国际知名学术期刊《自然—物理学》上发表。
该研究团队运用脉冲回波超声来测量样品中UTe2的弹性模量，结果显示这些样品展现出一个或两个超导相变。研究人员证明了无论是单相变还是双相变的样品，其剪切弹性模量在热力学上均保持连续，这直接证明了UTe2具有单组分超导序参量。研究人员进一步表明，超导性对沿a和c轴的压缩应变高度敏感，但对沿b轴的应变不敏感。基于此，他们建议使用单组分奇宇称校验序参量—特别是B2u序参量—其与他们的研究数据最兼容。
据悉，超导体中库珀对的微观机制在序参量的对称性上留下了印记。UTe2之前被推测拥有多组分序参量，其依据之一是部分样品中显著出现的两步超导相变。但最新对新一代样品的实验观察对此解释提出了挑战，并强调了对序参量对称性进行直接探测的必要性。
附：英文原文
Title: Single-component superconductivity in UTe2 at ambient pressure
Author: Theuss, Florian, Shragai, Avi, Grissonnanche, Gal, Hayes, Ian M., Saha, Shanta R., Eo, Yun Suk, Suarez, Alonso, Shishidou, Tatsuya, Butch, Nicholas P., Paglione, Johnpierre, Ramshaw, B. J.
Issue&Volume: 2024-05-09
Abstract: The microscopic mechanism of Cooper pairing in a superconductor leaves its fingerprint on the symmetry of the order parameter. UTe2 has previously been inferred to have a multi-component order parameter, in part due to the apparent presence of a two-step superconducting transition in some samples. However, recent experimental observations in newer-generation samples have raised questions about this interpretation, pointing to the need for a direct probe of the order parameter symmetry. Here we use pulse-echo ultrasound to measure the elastic moduli of UTe2 in samples that exhibit both one and two superconducting transitions. We demonstrate the absence of thermodynamic discontinuities in the shear elastic moduli of both single- and double-transition samples, providing direct evidence that UTe2 has a single-component superconducting order parameter. We further show that superconductivity is highly sensitive to compression strain along the a and c axes but insensitive to strain along the b axis. This leads us to suggest a single-component, odd-parity order parameter—specifically the B2u order parameter—as most compatible with our data.
DOI: 10.1038/s41567-024-02493-1
Source: https://www.nature.com/articles/s41567-024-02493-1