# Ultraslow fluctuations in the pseudogap states of HgBa$_{2}$CaCu$_{2}$O$_{6+d}$

## TL;DR

This study investigates ultraslow magnetic fluctuations in the pseudogap states of HgBa$_{2}$CaCu$_{2}$O$_{6+d}$ using nuclear magnetic resonance, revealing doping-dependent relaxation behaviors and the presence of ultraslow fluctuations in underdoped and optimally doped samples.

## Contribution

The paper provides new insights into ultraslow fluctuations in pseudogap states of a high-$T_c$ cuprate, highlighting doping-dependent relaxation rate peaks and their implications.

## Key findings

- Peak in 1/T_{2L} at 220-240 K in underdoped and optimally doped samples.
- No peak observed in overdoped sample.
- Ultraslow fluctuations are present in pseudogap states.

## Abstract

We report the transverse relaxation rates 1/$T_2$'s of the $^{63}$Cu nuclear spin-echo envelope for double-layer high-$T_c$ cuprate superconductors HgBa$_{2}$CaCu$_{2}$O$_{6+d}$ from underdoped to overdoped. The relaxation rate 1/$T_{2L}$ of the exponential function (Lorentzian component) shows a peak at 220$-$240 K in the underdoped ($T_c$ = 103 K) and the optimally doped ($T_c$ = 127 K) samples but no peak in the overdoped ($T_c$ = 93 K) sample. The enhancement in 1/$T_{2L}$ suggests development of the zero frequency components of local field fluctuations. Ultraslow fluctuations are hidden in the pseudogap states.