Skip to main content

Questions tagged [greens-functions]

Questions related to Green's functions and their role in matter modeling.

Filter by
Sorted by
Tagged with
4 votes
0 answers
32 views

Generation of the eletromagnetic wave or electric current by the photo-excitation

Suppose there is an incident photo with a specific frequency hitting the material; the incident photo is absorbed by this material. Meanwhile, the material is excited by this incident photo and ...
Kieran's user avatar
  • 753
3 votes
1 answer
49 views

The Dynamic Constant Matrix for the Green Function in the Thermal Conductance Calculation

When computing the thermal transmission coefficient, the green function needs to be computed first; for example, $G^{R}_{scattering\:region}=\left[\left(\omega+i0^{+}\right)^{2}I-D\right]^{-1}$, where ...
Kieran's user avatar
  • 753
2 votes
0 answers
61 views

Difference of the Transmission Coefficient between Thermal and Charge Conductance by Nonequilibirum Green Function Method

The equation 57 in the reference [Jian-Sheng Wang, Jian Wang and J. T. Lu, Quantum thermal transport in nanostructures, Eur. Phys. J. B 62, 381 (2008)] explains the the transmission coefficient for ...
Kieran's user avatar
  • 753
2 votes
0 answers
49 views

BZ grid and susceptibility for numerical Pauli limit calculation

I am trying to calculate the Pauli limit for a superconducting material with Hamiltonian $H_0$ and an external magnetic field contribution $H_p$. I find the matsubara greens function as $\hat{G} = [i\...
gx824's user avatar
  • 21
3 votes
1 answer
76 views

Implemetation of NEGF in TranSIESTA

I have a general query regarding NEGF approach: In TranSIESTA code, when self-energy of the electrodes is calculated, does it require the coupling elements of the electrode with the central scattering ...
sushil's user avatar
  • 329
3 votes
0 answers
63 views

Hilbert transform on the Bethe Lattice

In order to compute the local Green's function on the Bethe lattice, it is necessary to perform a Hilbert transform $$G_{loc}(\omega) = \int \frac{DOS(\varepsilon)}{\omega-\varepsilon} \text{d}\...
NehZio's user avatar
  • 146
7 votes
0 answers
144 views

Calculation of charge transport with the non-orthogonal basis Hamiltonian based on the non-equilibrium Green's function method

I am thinking about one question. If the Hamiltonian matrix is based on the non-orthogonal basis, how to compute the charge conductance with the Non-Equilibrium Green's Function (NEGF) method. Suppose ...
Kieran's user avatar
  • 753
6 votes
2 answers
332 views

How can I get the projected density of states within the Green's function method?

I have this Green's function matrix $G^r= (E \mathbb{I} - \hat{H})^{-1}$ in the $|\textrm{site}\rangle\otimes|\textrm{orbital}\rangle\otimes|\textrm{spin}\rangle$ Hilbert space, and I am curious if ...
jazzloaf's user avatar
5 votes
0 answers
103 views

Good books about green's function method [closed]

I am trying to learn to do Green's function calculations. Are there any good introductory books about the Green's function method?
andy90's user avatar
  • 305
1 vote
0 answers
37 views

Invariance of magnetic susceptibility when rotating a tight-binding Hamiltonian [closed]

We know the magnetic susceptibility for a non-interacting tight-binding model has the Lindhardt form, for which I express as product of matsubara Green's functions $$\chi^{(0)}(q,\omega)=-\beta\sum_{k,...
Zhihui's user avatar
  • 111
3 votes
0 answers
62 views

Green function KMS boundary condition [closed]

How to obtain the relation between $G_{ab}(\tau,0,0,0)$ and $G_{ab}(\beta-\tau,0,0,0)$ for two-particle fermion Green function $$G_{ab}(\tau_1,\tau_2,\tau_3,\tau_4)=\langle \mathcal{T}a^\dagger(\tau_1)...
Zhihui's user avatar
  • 111
7 votes
0 answers
143 views

Tools for symbolic calculations of quantum transport using the Keldysh NEGF formalism [closed]

I am looking for tools for symbolic calculation of quantum transport or quantum mechanics that involves Keldysh NEGF (non-equilibrium Green's function) formalism. The closest tool I heard/seen is <...
Aschoolar's user avatar
  • 171
15 votes
2 answers
1k views

About the surface Greens function method for calculating the surface state

Currently I'm using some software package to do the data analysis from the DFT calculation so that I can study the surface state of some topological insulator. I found that the method they use is ...
JensenPang's user avatar
  • 2,903
28 votes
3 answers
3k views

Given that Kohn-Sham DFT is strictly a ground-state method (at 0 K), how is it sufficient to describe materials in real-life applications?

Kohn-Sham DFT appears to be so popular even though it is strictly a ground-state method - all calculations are done at 0 K. How then, is it so popular when describing materials that have real-life ...
livars98's user avatar
  • 2,506
14 votes
1 answer
138 views

Approximation of Dyson's Equation

I've been trying to learn about Green's function in the context of computational chemistry by reading Szabo and Ostlund's Modern Quantum Chemistry. I've reached a section about the one particle many ...
Tyberius's user avatar
  • 15.6k
13 votes
1 answer
1k views

Why is the Nonequilibrium Green’s function (NEGF) method for quantum transport not implemented in plane wave codes like VASP and Quantum Espresso?

DFT codes like Siesta, QuantumATK, Questaal, and Smeagol having localized basis sets have NEGF implementations available. But not in plane wave codes like VASP and Quantum Espresso. Why is it so?
Thomas's user avatar
  • 9,142