We compare various recently proposed spin-battery devices which provide source of spin current. We sort them into three types according to the chemical-potential setup: the symmetric dipolar, the asymmetric dipolar, and the unipolar spin batteries. We propose a model in which these three different types of spin battery are coupled to the same quantum dot to generate spin-current transport. We find that the dipolar spin batteries give similar results while very different results are found for the unipolar device.

• Received 9 December 2003

DOI:https://doi.org/10.1103/PhysRevB.69.205312