1212.0530 (S. -H. Baek et al.)

Evidence of a critical hole concentration in underdoped
YBa$_2$Cu$_3$O$_y$ single crystals revealed by $^{63}$Cu NMR    [PDF]

S. -H. Baek, T. Loew, V. Hinkov, C. T. Lin, B. Keimer, B. Büchner, H. -J. Grafe

We report a $^{63}$Cu NMR investigation in detwinned YBa$_2$Cu$_3$O$_y$ single crystals, focusing on the highly underdoped regime (y=6.35-6.6). Measurements of both the spectra and the spin-lattice relaxation rates of $^{63}$Cu uncover the emergence of static order at a well-defined onset temperature $T_0$ without a known order parameter as yet. While $T_0$ is rapidly suppressed with increasing hole doping concentration $p$, the spin pseudogap was identified only near and above the doping content at which $T_0\rightarrow 0$. Our data indicate the presence of a critical hole doping $p_c\sim 0.1$, which may control both the static order at $pp_c$.

View original: http://arxiv.org/abs/1212.0530