28 August 2022 to 2 September 2022
Science and Technology Campus, University of Parma
Europe/Rome timezone
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Superconductivity nearby quantum critical point in hole-doped organic strange metal $\kappa$-(ET)$_{4}$Hg$_{3-\delta}$Br$_{8}$

P-MON-17
29 Aug 2022, 17:20
1h 40m
Science and Technology Campus, University of Parma

Science and Technology Campus, University of Parma

University of Parma, Italy
Poster Superconductivity Posters

Speaker

Dr Dita Puspita Sari (College of Engineering, Shibaura Institute of Technology)

Description

The hole-doped organic superconductor $\kappa$-(ET)$_{4}$Hg$_{3-\delta}$Br$_{8}$, ($\kappa$-HgBr), where $\delta$=11% and
ET=bis(ethylenedithio)tetrathiafulvalene, has been the key to bridge the knowledge gap between half-filled organics and doped cuprate systems. Nonetheless, the isotropic triangular lattice of ET dimers of $\kappa$-HgBr, unlike the square lattice in cuprates, is suspected responsible for its susceptibility which is well scaled with the organic spin liquid insulator $\kappa$-(ET)$_{2}$Cu$_{2}$(CN)$_{3}$. However, both $\kappa$-HgBr and cuprate have a region at high temperature and high-pressure corresponding to the $strange$ $metallic$ state where resistivity exhibits a linear temperature dependence which is non-Fermi-liquid (non-FL) behavior. In $\kappa$-HgBr this non-FL region gradually changed to an FL state by pressure [1], like the change of metallic state from optimal to overdoped cuprates. The $^{13}$C-NMR concluded that the antiferromagnetic fluctuations contribute to the origin of the non-FL in $\kappa$-HgBr [3]. This evidence may locate superconducting $\kappa$-HgBr nearby quantum critical point (QCP) in between FL and localized states, where in its non-FL state the incoherent conductivity was observed [1,3].

Our zero-field $\mu^+$SR experiment showed the relaxation rate from around 10 K down to 0.3 K is temperature-independent. This is a high possibility of the superconducting state that preserved time-reversal symmetry. There was almost no change in the 120 Oe of transverse-field-$\mu^{+}$SR time spectra, at 0.3 K and above the superconducting temperature $T_{c}$ = 4.6 K, indicating that the London penetration depth is longer than a $\mu$m order, while we estimate the lower critical field, $H_{c1} = 25(5)$ Oe. These could be an indication of a strong-coupling superconductor. We will discuss a possible mechanism of preserved time-reversal Cooper pairing formation from strong-coupling non-FL metal with geometrical frustration.

[1] H. Taniguchi, et al., J. Phys. Soc. Jpn. 11, 113709 (2007)
[2] Y. Eto, et al., Phys. Rev. B 81, 212503 (2010)
[3] H. Oike, et al., Nat. Commun. 8, 756 (2017)

Primary author

Dr Dita Puspita Sari (College of Engineering, Shibaura Institute of Technology)

Co-authors

Mr Miki Kaito (College of Engineering, Shibaura Institute of Technology) Dr Utami Widyaiswari (Graduate School of Science, Hokkaido University) Dr Isao Watanabe (RIKEN Nishina Center) Prof. Hiromi Taniguchi (Department of Physics, Saitama University) Prof. Yasuyuki Ishii (College of Engineering, Shibaura Institute of Technology)

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