Generic model for current collapse in spin-blockaded transport

A decrease in current with increasing voltage, often referred to as negative differential resistance (NDR), has been observed in many electronic devices and can usually be understood within a one-electron picture. However, NDR has recently been reported in nanoscale devices with large single-electron charging energies which require a many-electron picture in Fock space. This paper presents a generic model in this transport regime leading to a simple criterion for the conditions required to observe NDR and shows that this model describes the recent observation of multiple NDR's in spin-blockaded transport through weakly coupled-double quantum dots quite well. This model clearly shows how a delicate interplay of orbital energy offset, delocalization, and Coulomb interaction leads to the observed NDR under the right conditions, and also aids in obtaining a good match with experimentally observed features. We believe that the basic model could be useful in understanding other experiments in this transport regime as well.