Quantum transport

Two-dimensional (2D) crystals have emerged as a new class of materials with diverse electronic properties. This is best exemplified by graphene, and more recently by transition metal dichalcogenides. We have recently discovered that a new 2D material, black phosphorus (BP), can host high quality 2D electron system (2DES) with carrier mobility up to 10,000 cm2/Vs at low temperatures. The high mobility enables us to explore the quantum transport in the new 2DES. In particular, we have observed, for the first time, quantum oscillations and more recently integer quantum Hall...

Quantum transport theory yields the celebrated Landauer formula for the conductance of a two-terminal device at zero bias in terms of T(EF,0), the transmission coefficient T(E,V) evaluated at the Fermi energy EF and V=0. For finite biases, one must use the nonequilibrium Green’s function (NEGF) method, which entails substantial difficulties. Instead of NEGF calculations, T(E,0) is often interpreted as representing transport at V=E/e. This practice is seriously flawed. In its stead, we employ quantum transport theory to derive a simple finite-bias analog of the...