Department of Physics, University of Florida, Gainesville, Florida 32611-8440, USA.
Phys Rev Lett. 2011 Jul 15;107(3):037201. doi: 10.1103/PhysRevLett.107.037201. Epub 2011 Jul 11.
We present experimental data and a theoretical interpretation of the conductance near the metal-insulator transition in thin ferromagnetic Gd films of thickness b ≈ 2-10 nm. A large phase relaxation rate caused by scattering of quasiparticles off spin-wave excitations renders the dephasing length L(ϕ) ≲ b in the range of sheet resistances considered, so that the effective dimension is d = 3. The conductivity data at different stages of disorder obey a fractional power-law temperature dependence and collapse onto two scaling curves for the metallic and insulating regimes, indicating an asymmetric metal-insulator transition with two distinctly different critical exponents; the best fit is obtained for a dynamical exponent z ≈ 2.5 and a correlation (localization) length critical exponent ν- ≈ 1.4 (ν+ ≈ 0.8) on the metallic (insulating) side.
我们呈现了在厚度约为 2-10nm 的薄铁磁 Gd 薄膜中，金属-绝缘相变附近的电导的实验数据和理论解释。由于准粒子散射自旋波激发导致的大相位弛豫率，在考虑的薄片电阻范围内，失相长度 L(ϕ)≲b，因此有效维度为 d = 3。在不同无序阶段的电导率数据遵循分数幂律温度依赖性，并在金属和绝缘区域上collapse 到两个标度曲线，表明具有两个明显不同临界指数的不对称金属-绝缘相变；最佳拟合是对于动态指数 z ≈ 2.5 和相关（局域化）长度临界指数 ν- ≈ 1.4（ν+ ≈ 0.8）在金属（绝缘）侧。
