Validate iterative GKBA for time- and spin-dependent quantum transport

Determine whether the iterated generalized Kadanoff–Baym ansatz (iGKBA) resolves the violations and inaccuracies identified for the generalized Kadanoff–Baym ansatz in time- and spin-dependent quantum transport while maintaining linear computational scaling and supporting many-body interactions in multiterminal junctions.

Background

The paper finds that the standard generalized Kadanoff–Baym ansatz (GKBA) fails to reproduce spin pumping and spin-transfer-torque dynamics in two-terminal spintronic junctions because it neglects relevant off-diagonal two-time Green-function components and can violate spin and charge conservation. The extended GKBA is likewise stated not to resolve these issues.

The authors identify a recently proposed iterated GKBA (iGKBA) as a possible remedy that could preserve linear scaling and incorporate many-body interactions in multiterminal junctions. However, whether iGKBA actually resolves the deficiencies observed for time- and spin-dependent quantum transport remains unestablished.

References

Nevertheless, another very recently proposed scheme iterating GKBA further (iGKBA) holds promise (yet to be demonstrated) to resolve the issues we found in time- and spin-dependent quantum transport, while maintaining linear scaling and being able to include many-body interactions within multiterminal junctions.

— Benchmarking the generalized Kadanoff-Baym ansatz and second-order adiabatic expansion using time-dependent spintronic effects: Spin pumping, torque, and inertia  (2609.26694 - Varela-Manjarres et al., 22 Sep 2026) in Section 4.1, Conclusions