KrylovSelfEnergy

class KrylovSelfEnergy(save_self_energies=None, lambda_min=None, sparse_threshold=None, storage_strategy=None)

Self-energy calculator based on the Krylov method. The Krylov scheme uses an iterative approach for getting a subset of all the electrode modes.

Parameters:
  • storage_strategy (SaveInMemory | StoreOnDisk | NoStorage) – The way self energies are stored between iterations.
    Default: SaveInMemory()
  • lambda_min (float > 0) – The smallest logarithmic decrement of a mode to take into account.
    Default: 0.1
  • sparse_threshold (float > 0) – Self energies (in Hartree) smaller than this value treated as 0 when storing as sparse matrix.
    Default: 1e-12
  • save_self_energies

    Deprecated since version 2017.0: Use storage_strategy instead.

lambdaMin()
Returns:The smallest logarithmic decrement of a mode
Return type:float
saveSelfEnergies()

Deprecated since version 2017.0.

sparseThreshold()
Returns:Values treated as 0.
Return type:float
storageStrategy()
Returns:The way self energies are stored between iterations.
Return type:SaveInMemory | StoreOnDisk | NoStorage

Usage Examples

Define that the self energy on the real contour is calculated with the Krylov method. Only modes with a decay slower than 0.05 are included.

device_algorithm_parameters = DeviceAlgorithmParameters(
    self_energy_calculator_real=KrylovSelfEnergy(lambda_min=0.05),
)

Examples on how to use the storage_strategy parameter can be found in the Usage Examples of RecursionSelfEnergy.

Notes

KrylovSelfEnergy uses the iterative Krylov subspace method by H. H. Sørensen et. al. [qSrensenHP+08], [qSrensenHP+09] for calculating the self energy matrix. The lambda_min parameter determines the size of the Krylov subspace. In the limit lambda_min goes to zero, the full space will be included.

References

[qSrensenHP+08]H. H. B. Sørensen, P. C. Hansen, D. E. Petersen, S. Skelboe, and K. Stokbro. Krylov subspace method for evaluating the self-energy matrices in electron transport calculations. Phys. Rev. B, 77:155301, Apr 2008. doi:10.1103/PhysRevB.77.155301.
[qSrensenHP+09]H. H. B. Sørensen, P. C. Hansen, D. E. Petersen, S. Skelboe, and K. Stokbro. Efficient wave-function matching approach for quantum transport calculations. Phys. Rev. B, 79:205322, May 2009. doi:10.1103/PhysRevB.79.205322.