近日，法国国家强磁场实验室的Marc-Henri Julien及其研究团队取得一项新进展。他们揭示了铜超导体自旋磁化率中的两能隙特征。相关研究成果已于2024年12月5日在国际知名学术期刊《自然—物理学》上发表。
本研究在高磁场抑制超导性的条件下，测量了YBa2Cu3Oy在低温下的自旋磁化率。研究发现，除了由无能隙激发产生的残余成分外，还有两个热活化贡献，它们分别来自不同的能隙。研究人员将这两个不同的能隙与短程电荷密度波和单态的形成联系起来，后者在某些量子自旋系统中也会出现。
这两种现象都在低温下对赝能隙有贡献，补充了高温下引发赝能隙行为的短暂反铁磁性。因此，研究人员提出，赝能隙应被视为一种复合性质，并且当未发生自旋条纹有序时，欠掺杂的铜氧化物倾向于形成短程自旋单态。
据悉，理解高温超导铜氧化物的一个根本障碍是，超导性的出现阻碍了低温下正常态性质的观测。说明这一问题的一个重要性质是自旋磁化率：正常态下随温度降低而减小的自旋磁化率被认为是赝能隙行为的证据。然而，由于关键的低温数据不可避免地反映了超导配对而非正常态，因此一直无法对这一减小给出明确的解释。
附：英文原文
Title: Signatures of two gaps in the spin susceptibility of a cuprate superconductor
Author: Zhou, Rui, Vinograd, Igor, Hirata, Michihiro, Wu, Tao, Mayaffre, Hadrien, Krmer, Steffen, Hardy, W. N., Liang, Ruixing, Bonn, D. A., Loew, Toshinao, Porras, Juan, Keimer, Bernhard, Julien, Marc-Henri
Issue&Volume: 2024-12-05
Abstract: A fundamental obstacle to understanding high-temperature superconducting cuprates is that the occurrence of superconductivity hinders the observation of the normal-state properties at low temperature. One important property illustrating this issue is the spin susceptibility: its decrease upon cooling in the normal state is considered as evidence of pseudogap behaviour. However, unambiguous interpretation of this decrease has been impossible, as the crucial low-temperature data inevitably reflect the superconducting pairing rather than the normal state. Here we measure the spin susceptibility of YBa2Cu3Oy at low temperature while suppressing superconductivity in high magnetic field. We found that there are two thermally activated contributions, each of which comes from a different gap, alongside a residual component due to gapless excitations. We relate these two distinct gaps to short-range charge density waves and to the formation of singlets, as occurs in certain quantum spin systems. Both phenomena contribute to the pseudogap at low temperature, supplementing the short-lived antiferromagnetism that initiates pseudogap behaviour at high temperatures. We, therefore, propose that the pseudogap should be regarded as a composite property and that, when not undergoing spin-stripe ordering, underdoped cuprates tend to form short-range spin singlets.
DOI: 10.1038/s41567-024-02692-w
Source: https://www.nature.com/articles/s41567-024-02692-w