Questions tagged [greens-functions]

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

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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
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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 ...
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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
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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
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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 ...
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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
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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
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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
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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
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13 votes
2 answers

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
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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
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14 votes
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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
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12 votes
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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
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