Module 8 : Andreev Reflection at ferromagnet and Superconductor Interfaces

Lecture 19 : Basic theory of Andreev reflections


(1) Determining the wavefunction
:

The distribution functions  and  MIDDLE are obtained by solving the scattering problem described by following Bogoliubov–de Gennes (BdG) equation [5]:

(9)

The single-particle Hamiltonian H0 is defined as

(10)

where , m is the effective mass of the electrons, and is the Fermi wavevector. The third term in eqn.(10) represents a δ function type scattering potential at the interface characterized by the dimensionless parameter Z. The exchange field hex(z) is given by

......(11)

and the SC gap is

........(12)

Therefore, the solution for BdG equation takes the form

........(13)

Where fσ(z) and gσ(z) are the electron and hole components of the wavefunction, respectively. Substituting eqn.(13) in eqn.(9) results;



 

.......(14)

Where uo and vo are the coherence factors defined as


 

(15)