Condensed-Matter Physics & Materials Science Seminar

"Strange superconductivity near an antiferromagnetic heavy-fermion quantum critical point"

Presented by Chung-Hou Chung, Department of Electrophysics, National Chiao-Tung University, Taiwan

Wednesday, July 24, 2019, 1:30 pm — ISB Bldg. 734 Conf. Rm. 201

The heavy fermion systems CeMIn5 with M = Co, Rh, Ir, the "115" family, provide a prototypical example of an exotic "strange superconductivity" where unconventional d-wave Cooper pairs get condensed out of an incoherent strange metal normal state, displaying non-Fermi liquid behavior such as: T-linear-resistivity, T-logarithmic specific heat coefficient and a T-power-law singularity in magnetic susceptibility, near an antiferromagnetic quantum critical point [1]. The microscopic origin of strange superconductivity and its link to antiferromagnetic quantum criticality of the strange metal state are still long-standing open issues. We propose a microscopic mechanism for strange superconductors, based on the coexistence and competition between the Kondo correlation and the quasi-2d short-ranged antiferromagnetic resonating-valence-bond (RVB)spin-liquid near the antiferromagnetic quantum critical point via a large-N (Sp(N)) Kondo-Heisenberg model and renormalization group analysis beyond the mean-field level [2]. In the absence of superconductivity, this effective field theory [3] can describe various aspects of strange metal state observed in Ge-substituted YbRh2Si2 [4] close to the field-tuned Kondo breakdown quantum critical point. The interplay of these two effects between the Kondo and RVB physics provides a qualitative understanding on how superconductivity emerges from the strange metal state and the observed superconducting phase diagrams for CeMIn5 [1,2]. References: [1] C. Petrovic et al. J. Phys. Condens. Matt. 13, L337 (2001); S. Zaum et al. Phys. Rev. Lett. 106, 087003 (2011). [2] Y. Y. Chang, F. Hsu, S. Kirchner, C. Y. Mou, T. K. Lee, and C. H. Chung, Phys. Rev. B 99, 094513 (2019). [3] Y. Y. Chang, S. Paschen, and C. H. Chung, Phys. Rev. B 97, 035156 (2018). [4] J. Custers et al, Nature (London) 424, 524 (2003); J. Custers et al. Phys. Rev. Lett. 104, 186402 (2010).

Hosted by: Alexei Tsvelik

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