Hot-keys on this page
r m x p toggle line displays
j k next/prev highlighted chunk
0 (zero) top of page
1 (one) first highlighted chunk
# Copyright 2011-2013 Kwant authors.
# This file is part of Kwant. It is subject to the license terms in the file
# LICENSE.rst found in the top-level directory of this distribution and at
# http://kwant-project.org/license. A list of Kwant authors can be found in
# the file AUTHORS.rst at the top-level directory of this distribution and at
import numpy as np
from ..solvers.common import SMatrix
__all__ = ['two_terminal_shotnoise']
r"""Compute the shot-noise in a two-terminal setup.
In a two terminal system the shot noise is given by `tr((1 - t*t^\dagger) *
smatrix : `~kwant.solvers.common.SMatrix` instance
A two terminal scattering matrix.
noise : float
Shot noise measured in noise quanta `2 e^3 |V| / pi hbar`.
32 ↛ 33line 32 didn't jump to line 33, because the condition on line 32 was never true if not isinstance(smatrix, SMatrix):
raise NotImplementedError("Noise expressions in terms of Green's "
"functions are not implemented.")
if len(smatrix.lead_info) != 2:
raise ValueError("Only works for two-terminal systems!")
t = smatrix.submatrix(smatrix.out_leads, smatrix.in_leads)
ttdag = np.dot(t, t.conj().T)
return np.trace(ttdag - np.dot(ttdag, ttdag)).real
# A general multi-terminal routine for noise would need to also have the
# voltages at various leads as input. (See
# http://arxiv.org/abs/cond-mat/9910158) It could still be based on
# smatrix._a_ttdagger_a_inv, i.e. be also valid also for self-energy leads,
# provided that only true transmission blocks are used. As long as nobody needs
# it though, it does make little sense to make such a routine.