Favago Transport Programming Interface

Introduction

Interfaces

root/

root/utils

Data structures

Examples







SNSJosephson

  Copyright (C) 2009-2015 Peter Rakyta, Ph.D.
  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
  You should have received a copy of the GNU General Public License
  along with this program.  If not, see http://www.gnu.org/licenses/.

Description

Returns an interface to calculate the DC Josephson current in the SNS arrangement.

Syntax

interface = SNSJosephson( varargin )

Parameters
varargin Optional parameters given by a sequence ...'name', value,... . Possible parameter names are the following:

  • width

    Integer. Gives the number of the atomic sites in the cross section of the ribbon.

  • height

    Integer. Gives the height of the ribbon in units of the lattice vector.

  • B

    The strength of the magnetic field in the units of Tesla.

  • T

    The absolute temperature in Kelvins.

  • filenameIn

    Input filename for the xml input structure.

  • filenameOut

    Output filename for the xml input structure.

  • E

    The energy used in the calculations.

  • EF

    The Fermi energy in eV.

  • phi

    A vector of pair potential phases in the left (1st) and right (2nd) superconductor

  • silent

    Set true for suppress the displaying of the output messages.

  • ContactPotInterface

    A function handle of the contact potential in the interface regions.

  • Set true for calculet the Green's function of the scattering region is calculated from Hamiltonian, or false (default) to use the Dyson Equation.

  • scatterPotential

    A function handle $$y=f( coordinates)$$ of the potential across the junction in case gfininvfromHamiltonian is true.

  • q

    The tranverse momentum for transverse computations.

Attributes

Exported interfaces

Methods

SNSJosephson::Transport

Calculates the transmission probability of the BdG quasiparticles in the SNS arrangement.

Syntax

[Conductance,ny,DeltaC] = interface.Transport(Energy, B)

Parameters
Energy The energy to be used in the calculations.
B The strength of the magnetic field in the units of Tesla.

Return
Conductance The calculated conductance in the units of $$2h/e$$.
ny The number of the open channels in the leads.
DeltaC The standard deviation of the calculated transmission probabilities.






SNSJosephson::CurrentCalc_continuum

Calculates the Josephson current induced by the continuous scattering states.

Syntax

[currentvec, current_surf] = interface.CurrentCalc_continuum( DeltaPhi_vec, varargin )

Parameters
DeltaPhi_vec The vector of the superconducting phase differences.
varargin Optional parameters given by a sequence ...'name', value,... . Possible parameter names are the following:

  • Edb

    The number of the energy points over the contour integral.

Return
currentvec The vector of the integrated Josephson current in the energy range of the scattering states for each phase difference given in the parameter DeltaPhi_vec.
current_surf A matrix containing the calculated Josephson current for each phase difference (rows) and energy point (columns).






SNSJosephson::CurrentCalc_discrete

Calculates the Josephson current induced by the continuous scattering states.

Syntax

currentvec = interface.CurrentCalc_discrete( DeltaPhi_vec, varargin )

Parameters
DeltaPhi_vec The vector of the superconducting phase differencies.
varargin Optional parameters given by a sequence ...'name', value,... . Possible parameter names are the following:

  • range

    String. Set 'ABS' (default) for the Andreev bound states, 'NBS' for the normal bound states, 'CONT' for the scattering states, or 'ALL' for calculating all ranges at once.

  • Edb

    The number of the energy points over the contour integral.

  • DeltaPhi

    A parameter to control the incident angle of the integration contour near the real axis. (Default value is $$\Delta\Phi=0.5\pi$$.

  • Evec

    The complex energy points in case of custom integration path.

Return
currentvec The vector of the Josephson current summed over the discrete bound states for each phase difference given in the parameter DeltaPhi_vec.






SNSJosephson::CreateHandlesForMagneticField

Creates function handles of the vector potentials and apply the magnetic filed in the ribbon Hamiltonians.

Syntax

interface.CreateHandlesForMagneticField()







SNSJosephson::createCurrentOperator

Calculates the matrix representation of the current operator and the inverse Greens function of the scattering region.

Syntax

[current_op, gfininv] = interface.createCurrentOperator( varargin )

Parameters
varargin Optional parameters given by a sequence ...'name', value,... . Possible parameter names are the following:

  • ribbon

    An instance of the interface Ribbon storing the Hamiltonians of the unit cell in the normal region.

Return
current_op The matrix representation of the current operator.
gfininv The inverse Greens function of the scattering region.






SNSJosephson::getBandWidth

Determines the band width in the leads and in the scattering region. The results are stored in the attribute BandWidth.

Syntax

interface.getBandWidth()







SNSJosephson::create_scatter_GreensFunction

Calculates the surface Greens function of the antidot. Sets the attribute gfininv to the calculated results.

Syntax

interface.create_scatter_GreensFunction( varargin )

Parameters
varargin Optional parameters given by a sequence ...'name', value,... . Possible parameter names are the following:

  • onlyAtEnds

    Logical value. Set true to calculate the Greens function only at the ends of the scattering region, or false (default) to calculate the Greens function in several inner slabs as well.

  • gauge_trans

    Logical value. Set true (default) to perform gauge transformation on the Green's function and on the Hamiltonians, or false otherwise.

  • ribbon

    An instance of the interface Ribbon storing the Hamiltonians for the Dyson's equation. (Needed for parallel computations.)






SNSJosephson::GetWorkspace

Return a class handle ws_SNSJosephson of the workspace of the interface SNSJosephson. Changes in fields of the workspace are not always safe, since the reinitialization of the interface is not performed.

Syntax

interface.GetWorkspace( )

Return
ret An instance of class handle ws_antidot.