quantumtransport

Quantum transport studies how quantum mechanics governs the movement of particles, typically electrons, through materials and nanoscale systems. It highlights coherence, interference, and the quantization of charge, leading to transport phenomena that differ from classical diffusion. The field covers mesoscopic devices where phase coherence persists, as well as molecular junctions and other ultra-small structures.

The main frameworks are Landauer–Büttiker, which relates conductance to transmission probabilities, and non-equilibrium Green's function (NEGF) methods for open systems under bias. Linear response is described by the Kubo formula; time-dependent transport uses extensions. Computationally, quantum transport often combines tight-binding or ab initio electronic structure with NEGF.

Key phenomena include quantized conductance in ballistic quantum point contacts, with steps in units of 2e^2/h; Coulomb blockade in small islands; weak localization and universal conductance fluctuations due to interference; and thermoelectric or spin-dependent transport in nanostructures and topological materials.

Experimental platforms encompass semiconductor heterostructures, graphene and other two-dimensional materials, carbon nanotubes, quantum dots, and molecular junctions. Quantum transport is central to nanoelectronics, spintronics, and quantum information devices, as well as to phonon-mediated transport and thermoelectric effects.

Challenges include incorporating many-body interactions, inelastic scattering, and decoherence, and improving first-principles modeling of electron-phonon coupling. Ongoing work extends theories to strongly correlated, time-dependent, and non-equilibrium regimes.