学术报告： Superconducting ground state of new superconductors A2Cr3As3 (A=K and Cs) and ThFeAsN investigated using uSR measurements

报告人：Devashibhai Adroja      Senior Scientist， ISIS Facility, Rutherford Appleton Laboratory, UK

时间: 6月22号（周四）上午9:30

地点: 田家炳楼南205室

邀请人： 董帅

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摘要：The superconducting state of the newly discovered superconductors A2Cr3As3 (A=K and Cs, TC=6 K and 2.1 K, respectively) and ThFeAsN (TC=30K) have been investigated using magnetization and muon-spin relaxation or rotation (μSR)measurements. Our analysis of the transverse field (TF) mSR results of A2Cr3As3 (A=K and Cs) shows that the temperature dependence of the superfluid density, obtained from TF-mSR measurements, fits better toa nodal gap structure than an isotropic s-wave model. Therefore our μSR analysis is more consistent with having line nodes than being fully gapped in A2Cr3As3 (A=K and Cs). This result is in agreement with the results of the penetration depth measured using a tunnel diode oscillator technique on A=K. Further our zero-field (ZF) μSR measurements do reveal very weak evidence of the spontaneous appearance of an internal magnetic field below the transition temperature. This observation suggests that the electrons are paired via unconventional channels such as spin fluctuations, as proposed on the basis of theoretical models. On the other hand the analysis of TF-mSR results of ThFeAsN shows a possibility of an isotropic s-wave gap. We will present the results of the magnetic penetration depth λL, superconducting carrier density ns, and effective-mass enhancement m* estimated from the TF-mSR measurements of these three compounds.

Bio: Adroja博士是Rutherford Appleton Laboratory的高级研究员，主要负责MERLIN光谱仪，同时也是南非约翰内斯堡大学的客座教授。在用中子散射和μSR技术研究强关联电子体系方面已有24年的经验。1991年获印度理工学院孟买分校博士学位，随后担任南安普顿大学研究员。1999年加入ISIS，2007年至今为ISIS的高级研究员。是发现近藤绝缘体CeRhS以及相关材料Ce(NiCo)Sn和CePdSb的先锋者。目前在强关联电子体系的自旋和电荷间隙形成领域做出了重要贡献，并发表了两篇综述文章。在同行评审期刊上共发表290多篇的文章。