Abstract
A scheme of an all-electrical spin conductance diode is proposed that uses a step-like quantum wire with Rashba spin-orbit interaction, connected to two leads with different width. It is shown that a very large spin conductance can be obtained when electrons transmit from the narrow lead to the wide lead, however, it vanishes or becomes very small when the transport direction is reversed. This difference is revealed to arise from the different local density of electron states of the quantum wire, which is dependent on the direction of bias. The spin conductance in the proposed structure can be generated and manipulated by purely electrical means and with strong a robustness against disorder, displaying the feasibility of this structure for a real application.