Mailman 3 May 2024 - Kwant-discuss

To to separate spins, electron and hole
by Khani Hosein Oct. 11, 2024

Oct. 11, 2024

Dear all, I am using Kwant to study a system with both spins and electron and hole, so the hopping matrix is 4X4. Now I want to know how to separate the spins, electron and hole. I study this through the "2.6. Superconductors: orbital degrees of freedom, conservation laws and symmetries" smatrix = kwant.smatrix(syst, energy) data.append(smatrix.submatrix((0, 0), (0, 0)).shape[0] -smatrix.transmission((0, 0), (0, 0)) +smatrix.transmission((0, 1), (0, 0))) I do not find more information about … [View More]

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[kwant] How to make a finite lead?
by 김봉수 June 12, 2024

June 12, 2024

Dear kwant users, I am trying to reproduce the paper following. https://arxiv.org/abs/1110.4280 (in this paper, fig5, 6 will help to understand my questions.) What I’m struggling with now is to build a finite(not infinite, and not having any translational symmetry) lead as below. I wonder 1. I think "kwant.builder.SelfEnergyLead()” function might be proper thing to build a finite lead without any translational symmetry. Is it correct? 2. If it's right, when I run this code using … [View More]

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Leads self-energy matrix elements not ordered as system's hamiltonian_submatrix?
by wilson2048＠outlook.com June 4, 2024

June 4, 2024

Dear kwant community: I am investigating the `kwant.greens_function`。 I would like to get the lead self-energies and add to the original system Hamiltonian and then inverse it, thus obtaining the retarded green's function. I tested, but the resulted green's function is not identical to the one kwant calculated. I want to know the reason. Is it because what I describe in the title? Below is a minimal code example: ``` lat = kwant.lattice.square() def make_system(r=20, t=-1): def circle(… [View More]

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Questions About Magnetic Field Units in Landau_level.py for Landau Level Calculations
by ac76888＠sjtu.edu.cn May 30, 2024

May 30, 2024

Dear Kwant Community, I am writing to seek assistance with two issues I have encountered while using Kwant for solving transport problems. Your guidance would be greatly appreciated. 1. I am trying to calculate the Landau levels of monolayer graphene using the following Hamiltonian (python): ``` hamiltonian = """ + hbar_vF * (k_x * kron(sigma_0, sigma_x) + k_y * kron(sigma_0, sigma_y)) """ params = dict(hbar_vF=6.582) ``` In the documentation for the `discretize_landau` function, it … [View More]

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Current density for given lead currents
by X.-X. Zhang May 15, 2024

May 15, 2024

Hello Kwant community, I am considering a 6-terminal sample with 0,1,2,3 the voltage leads and 4,5 the current lead. Normally, with the conductance_matrix M found by kwant I can calculate transport properties (the voltages in vector V) as per the linear equation I = M V, given I = [0,0,0,0,1,-1]. Now I want to plot the current density corresponding to this transport state, but not sure how to do it. For instance, with wf = kwant.wave_function(sys, energy), I can have all scattering … [View More]

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wave function amplitude square meaning in kwant setting
by YIGITHAN GEDIZ May 14, 2024

May 14, 2024

Hi all, I have a scattering region, where for a given energy E, there is a single propagating mode. (kwant.wave_function(sys, E).shape[0] == 1) When I increase the energy a little bit without leaving the same band and plot the wavefunction again, I observe the same pattern in the scattering region, but the amplitudes are different. First one's maximum amplitude square is 6, whereas the other one's is 4, for instance. I observe that this is somehow related to the density of states at given … [View More]

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About the Warning "Hamiltonian breaks Conservation law, ignoring the symmetry in the computation.."
by GUIDO MENICHETTI May 4, 2024

May 4, 2024

Dear developers, dear all, I am Guido Menichetti, a Post-Doc at the University of Pisa. I am currently working on computing the Andreev reflection in a 3D hexagonal lattice system, incorporating the spin degree of freedom and utilizing wraparound techniques. To facilitate this, I have been following the Kwant tutorial available at https://kwant-project.org/doc/1.0/tutorial/tutorial5. In my approach, I define a "conservation law" to decompose the transmission function into four blocks: two … [View More]

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