Efficient spin transport along Si langle100rangle at room temperature

We find efficient spin transport in Si at room temperature in lateral spin valves (LSVs). When the crystal orientation of the spin-transport channel in LSVs is changed from $\langle$110$\rangle$, which is a conventional cleavage direction, to $\langle$100$\rangle$, the maximum magnitude of the spin signals is markedly enhanced. From the analyses based on the one-dimensional spin diffusion model, we can understand that the spin injection/detection efficiency in Si$\langle$100$\rangle$ LSVs is larger than that in Si$\langle$110$\rangle$ ones. We infer that, in Si-based LSVs, the spin detection efficiency of the pure spin current is related to the crystallographic orientation of the valley structures of the conduction band in Si.