Spin singlet-triplet relaxation times in Si double quantum dots

Recent observation of spin-sensitive transport in semiconductor quantum dots presents a new way of spin manipulation in nanoscale devices. Spin-flip processes are essential for understanding the potential of these systems. Following experiments by A.~C.~Johnson {\it et.al.} Phys.Rev.B {\bf 72}, 165308 (2005) and N.~Shaji {\it et.al.} [cond-mat/0708.0794] we calculate the relaxation times of different spin configurations in double quantum dots. For two-electron states, we evaluate the effects of leads on the spin-flip transitions, compare these effects with relevant spin-orbit and nuclear spin relaxation mechanisms, and calculate the electric current profile, including structure of the peaks and temperature dependence of the transport in the suppressed (`valley') region.