Muon spin rotation measurements of heterogeneous field response in overdoped ${\text{La}}_{2-x}{\text{Sr}}_x{\text{CuO}}_4$

Transverse-field muon spin rotation measurements of overdoped ${\text{La}}_{2-x}{\text{Sr}}_x{\text{CuO}}_4$ reveal a large broadening of the local magnetic field distribution in response to applied field, persisting to high temperatures. The field response is approximately Curie-Weiss-like in temperature and is largest for the highest doping investigated. Such behavior is contrary to the canonical Fermi-liquid picture commonly associated with the overdoped cuprates and implies extensive heterogeneity in this region of the phase diagram. A possible explanation for the result lies in regions of staggered magnetization about dopant cations, analogous to what is argued to exist in underdoped systems.

Figure 1

(Color online) [(a)–(e)] RRF asymmetries resulting from TF-$\mu \text{SR}$ measurements of single crystal ${\text{La}}_{1.7}{\text{Sr}}_{0.3}{\text{CuO}}_4$ in an applied field of ${\mu }_{0}H=3\text{T}$ at several temperatures. Field was applied perpendicular to the copper-oxide planes. (f) FFTs of three time spectra. The vertical dashed line shows the location of the applied field.

Figure 2

(Color online) (Left) The field dependence of the $\mu \text{SR}$ linewidth for each of the four crystals, extracted from Eq. (1). (Right) The slopes of the $\frac{d\lambda }{dH}$ curves as a function of temperature. Solid lines in both panels represent fits described in the text.

Figure 3

(Color online) The doping evolution of the heterogeneous field response. Top panel shows the increase of the absolute value of $\frac{1}{{\mu }_0}\frac{d\lambda }{dH}$ at $T=50\text{K}$ over that at $T=100\text{K}$. The following two panels show values of $C$ and $\Theta$, extracted from fits to Eq. (2). The line in the center panel is a guide to the eyes.

Figure 4

(Color online) (a) Raw asymmetry from TF-$\mu \text{SR}$ measurements of ${\text{La}}_{1.7}{\text{Sr}}_{0.3}{\text{CuO}}_4$ at $T=2\text{K}$ and ${\mu }_{0}H=3\text{T}$, applied perpendicular and parallel to the copper-oxide planes. (b) The relaxation rates resulting from fitting analogous spectra as that in (a), but over a range of temperatures.