Li Qi, Liu B T, Hu Y F, Chen J, Gao H, Shan L, Wen H H, Pogrebnyakov A V, Redwing J M, Xi X X
Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Phys Rev Lett. 2006 Apr 28;96(16):167003. doi: 10.1103/PhysRevLett.96.167003. Epub 2006 Apr 25.
We report a large normal-state magnetoresistance with temperature-dependent anisotropy in very clean epitaxial MgB2 thin films (residual resistivity much smaller than 1 microOmega cm) grown by hybrid physical-chemical vapor deposition. The magnetoresistance shows a complex dependence on the orientation of the applied magnetic field, with a large magnetoresistance (Delta(rho)/(rho)0=136%) observed for the field H perpendicular ab plane. The angular dependence changes dramatically as the temperature is increased, and at high temperatures the magnetoresistance maximum changes to H||ab. We attribute the large magnetoresistance and the evolution of its angular dependence with temperature to the multiple bands with different Fermi surface topology in MgB2 and the relative scattering rates of the sigma and pi bands, which vary with temperature due to stronger electron-phonon coupling for the sigma bands.
我们报道了通过混合物理化学气相沉积生长的非常清洁的外延MgB₂薄膜（剩余电阻率远小于1微欧厘米）中具有与温度相关各向异性的大正常态磁阻。磁阻表现出对外加磁场取向的复杂依赖性，对于垂直于ab平面的磁场H，观察到了大磁阻（Δρ/ρ₀ = 136%）。随着温度升高，角度依赖性急剧变化，并且在高温下磁阻最大值变为H平行于ab。我们将大磁阻及其角度依赖性随温度的演变归因于MgB₂中具有不同费米面拓扑结构的多个能带以及σ和π能带的相对散射率，由于σ能带更强的电子 - 声子耦合，它们随温度变化。
