Distribution of the low energy spin excitations in overdoped high Tc superconductor La_2-xSr_xCuO₄

Sr-doped La_2-xSr_xCuO₄ has been extensively studied in order to understand the mechanisms behind its high Tc superconductivity. Our earlier ⁶³Cu nuclear quadrupole resonance (NQR) experiments showed that the spin-lattice relaxation rate 1/T₁, which probes the low energy spin excitations locally, varies with NQR frequency due to the spatial variation of local hole concentration up to x~0.16 [1], but the large distribution of 1/T₁ caused by growing electronic inhomogeneity made ⁶³Cu NQR investigation difficult above x=0.16 at the time. Recent developments of the inverse Laplace transform (ILT) T₁ analysis technique overcame this difficulty, and we can now deduce the density distribution function P(1/T₁) of 1/T₁ (i.e. the histogram of the distribution of 1/T₁, and hence low energy spin excitations) [2-5]. We have carried out ⁶³Cu NQR experiments on the ⁶³Cu isotope enriched samples of overdoped (x>=0.16) La_2-xSr_xCuO₄. We will report the temperature-dependence of the inhomogenous distribution of 1/T₁ across the ⁶³Cu NQR spectrum by 2-dimensionally visualizing [5] the distribution via a T₁-resolved NQR lineshape.



References

[1] P. M. Singer, A. W. Hunt, and T. Imai, Phys. Rev. Lett. 88, 047602 (2002).

[2] P. M. Singer et al. Phys. Rev. B 101, 174508 (2020).

[3] A. Arsenault et al., Phys. Rev. B 101, 184505 (2020).

[4] J. Wang, W. Yuan, P.M. Singer, R.W. Smaha, W. He, J. Wen, Y.S. Lee, T. Imai, Nat. Phys. 17, 1109–1113 (2021).

[5] W. Yuan, J. Wang, P.M. Singer, R.W. Smaha, W. He, J. Wen, Y.S. Lee, T. Imai, arXiv:2209.15518