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A critical breakthrough is reached in resolving a long-standing issue on the mechanism of strange superconductivity in heavy electron materials

Research Highlight
Poster:Daw-Wei WangPost date:2019-03-19
Decorative image

Heavy fermion superconductivity has attracted much attention both theoretically and experimentally as it shows richness due to strong electron-electron correlations that is unaccounted for by the standard weak-coupling theory of superconductivity. It has been a long standing puzzle since early 2000’s that the unconventional superconductivity in heavy electron material CeMIn5 family (M=Co, Rh, Ir) emerges out of an incoherent “strange metal state” close to a magnetic quantum phase transition whose transport and thermodynamic properties are distinct from ordinary metals. The authors of this work provide a microscopic mechanism towards resolving this long standing issue via interplay of coexistence and competition between Kondo correlation (the screening of local f-electron magnetic moment by the d-orbital conduction electron spins) and the quasi-two-dimensional short-ranged antiferromagnetic correlation between adjacent f-electron moments in the vicinity of an antiferromagnetic quantum critical point (QCP). Within this theoretical framework of these two strong correlations, the strange metal state, which shows T-linear resistivity and T-logarithmic specific heat coefficient, comes as a result of the competition between these two correlations at higher temperatures near QCP. With decreasing temperatures, however, these two effects tend to co-exist and lead to un-conventional (d-wave pairing) superconductivity at ground state. This theory well explains the overall features of the superconducting and strange metal state at a semi-quantitative level; it also provides the first qualitative understanding on how superconductivity emerges from the strange metal state for CeMIn5.

 

Prof. Chung-Hou Chung is in National Chao-Tung University, the coordinator of TG8.

Prof. Chung-Yu Mou is in National Tsing Hua University, ex-director of NCTS

Prof. Tin-Kuo Lee, Academic Sinica, ex-director of NCTS

 

Link of this paper:

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.094513

 

 

Figure captions:

(a). The mean-field phase diagram of the CeMIn5 system. SC refers to the superconducting state, SL for short-ranged antiferromagnetic spin liquid state. (b). The schematic pressure p, magnetic field B and temperature T (p, B, T) phase diagram. SM stands for strange metal state, AF for antiferromagnetically ordered state, QC for quantum critical line. (c) The specific heat coefficient measured and computed both in the superconducting state and in the normal state. (d) The proposed phase diagram of CeMIn5 near QCP, explaining how superconductivity emerges out of SM state near QCP. LFL stands for the heavy Fermi liquid state with Kondo correlation.

 

 

 

 

 
Last modification time:2019-03-19 PM 12:52

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