양자물질초전도체창의연구소에서 Huazhong University of Science and Technology의 Yongkang Liu  교수님을 초청하여 아래와 같이 세미나를 개최합니다.

학과 구성원 여러분의 많은 참석을 부탁드립니다.

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○ Date/time: 4:00 pm, Oct 22nd, 2019

○ Place: 7th Floor of Samsung Library

○ Speaker: Prof. Yongkang Luo (Huazhong University of Science and Technology)

○ Title: To p or not to p? – O NMR of Sr2RuO4 under strain

○ Abstract:  Sr2RuO4 stands for one of the most fascinating unconventional superconductors. Although it shares the same crystal structure with 214 cuprates, the Tc is much lower. At its early stage since its discovery, theorists predicted a chiral p-wave order parameter d=z ̂(kx+iky). Experimental evidence for such chiral-p wave came from both unchanged spin susceptibility across Tc and time-reversal symmetry breaking at superconducting state. However, there also accumulated other evidence against it. Recently, scientists at MPI Dresden found a strong Tc peak under uniaxial strain, which is consistent with approaching a γ Fermi sheet van-Hove singularity. The absence of Tc cusp near zero strain suggested that a simple chiral p-wave is unlikely. Bulk and local experimental probe is necessary to elucidate this issue. In this talk, I will present our recent 17O NMR measurements of Sr2RuO4 under strain in both normal and superconducting states. Pronounced drops across Tc in Knight shifts are observed at both zero and vHs strains. These results, although need a better understanding, seem to exclude chiral p-wave as the most promising candidate.

References:
[1] Y. Luo et al, Phys. Rev. X 9, 021044 (2019).
[2] A. Pustogow*, Y. Luo* et al, Nature 574, 72 (2019).