Official Resources
- Homepage: https://github.com/Khem-Adhikari/WEYLFET
- Repository: https://github.com/Khem-Adhikari/WEYLFET
- License: MIT License (assumed open source)
Overview
WEYLFET is a specialized simulation tool built on top of the Kwant library, explicitly designed to model quantum transport in Weyl Semimetals (WSMs). It streamlines the setup of complex WSM Hamiltonians—including multi-node configurations, time-reversal breaking, and inversion breaking terms—and automates the calculation of transport signatures such as the chiral anomaly, Fermi arc surface transport, and disorder-induced transitions.
Scientific domain: Quantum Transport, Mesoscopic Physics
Target user community: Researchers simulating topological devices
Theoretical Methods
- Landauer-Büttiker Formalism: Calculating conductance $G = \frac{e^2}{h} \text{Tr}(t^\dagger t)$ via scattering matrices.
- Recursive Green's Functions: Algorithm used by Kwant to solve for the S-matrix of the scattering region.
- Weyl Hamiltonian: Lattice regularization of the Dirac equation to produce Weyl nodes (e.g., $H = \sin(k_x)\sigma_x + \sin(k_y)\sigma_y + (m - \cos k_x - \cos k_y - \cos k_z)\sigma_z$).
- Disorder Averaging: Introducing random onsite potentials or vacancies.
Capabilities
- Model Construction:
- Pre-defined 2-band and 4-band WSM lattice models.
- Tunable Weyl node separation and tilt.
- Transport Observables:
- Longitudinal/Hall conductance ($G_{xx}, G_{xy}$).
- Fano factor (Shot noise).
- Non-local voltage profiles.
- Disorder:
- Automated averaging over random configurations.
- Mean free path extraction.
Key Strengths
- WSM Specialization: Removes the overhead of "inventing" the WSM lattice model from scratch in Kwant. It provides correct, tunable models out of the box.
- Finite Size Physics: Unlike bulk tools, WEYLFET enables the study of finite devices, where Fermi arc surface states conduct in parallel with the bulk, a key experimental regime.
- Chiral Anomaly: Setup for parallel E and B fields to simulate the negative magnetoresistance signature of WSMs.
Inputs & Outputs
- Inputs:
- Model parameters (mass, hopping, node position).
- Device geometry (L, W, H).
- Disorder strength.
- Outputs:
- Conductance vs Energy/Field plots.
- Wavefunction maps (visualizing surface vs bulk flow).
Interfaces & Ecosystem
- Dependencies: Kwant, NumPy, Matplotlib.
- Visualization: Uses Kwant's plotting backend.
Performance Characteristics
- Efficiency: Inherits Kwant's efficient MUMPS solver usage.
- Scalability: Scaling is $O(W^3 L)$, limiting full 3D simulations to mesoscopic cross-sections (e.g., $30 \times 30$ atoms).
Comparison with Other Codes
- vs. Kwant (Vanilla): WEYLFET is a "physics pack" on top of Kwant. It saves the user from defining the system builder manually for standard WSM cases.
- vs. WannierTools: WannierTools calculates surface spectral functions (semi-infinite). WEYLFET calculates transport conductance (finite lead-device-lead).
Application Areas
- Fermi Arc Transport: Isolating surface contributions to conductivity.
- Disorder Transitions: Studying the phase diagram of WSMs under Anderson disorder.
Community and Support
- Development: Khem Adhikari.
- Source: GitHub.
Verification & Sources