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Highlight on one of our Atomistic Solutions: A Practical Guide to Study Photon-Assisted Quantum Transport.

August 9th, 2022

We are very pleased to announce the release of the latest tutorial which can be consulted on our Documentation Portal for everyone who wants to investigate photon-assisted quantum transport.

The electronic transport property can be obtained using the NanoDCAL code, which employs the nonequilibrium Green’s function technique (NEGF) within the Keldysh formalism in combination with DFT. The NEGF-DFT quantum transport formalism was first implemented by Guo, H. et al. [1], offering a first principles description of transport phenomena in real materials. However, the original NEGF-DFT approach was developed for problems without photons.

To calculate the photocurrent, the nanodevice is simulated out-of-equilibrium, which means that the voltage between source and drain is nonzero, which yields the microscopic details of the device material. Having determined the electronic Hamiltonian, the electron-photon interaction is included in the first-Born approximation. The usual electronic self-energy is then supplemented with a photon self-energy.

In a practical implementation, the source (and drain) current is composed of two parts: one is from the external bias (e.g., when no photons) and the other from the electron-photon interaction. If there is no light, only the first effect is observable, and one recovers the known electronic transport theory. The photocurrent technique implemented in NanoDCAL includes (optionally) noncollinear spin treatment and the spin-orbit interaction (SOI) which is important in many materials.

In this new tutorial (Direct link:, we carry out a photocurrent calculation revisiting the article “Generation and transport of valley-polarized current in transition-metal dichalcogenides” [2]. Shining circularly polarized light on the two-dimensional material WSe2 under external bias selectively delivers a net valley- and spin-polarized current.

This technique can be used for both bulk semiconductor materials, nanostructures, and a variety of 2D materials carbon-based materials.

For more information about the functionality of NanoDCAL, please visit our product page or the other documentation pages including installation and user manuals, technologies background, and of course plenty of other tutorials to get started:

Have a nice summer and see you soon with more posts about our tool features!

[1] Taylor, J., Guo, H., & Wang, J. (2001). Ab initio modeling of quantum transport properties of molecular electronic devices. Physical Review B, 63(24), 245407.

[2] L. Zhang, K. Gong, J. Chen, L. Liu, Y. Zhu, D. Xiao, and H. Guo. Generation and transport of valley-polarized current in transition-metal dichalcogenides Phys. Rev. B 90 (2014), p. 195428.