Novel phenomena in the electrical and thermal properties of 2D materials

Quantum-mechanical simulations are heralding a revolution in our capabilities to understand, predict, and design the properties and performance of novel materials and devices, and I'll try and illustrate this paradigm in the emergent field of 2D materials.First, using density-functional perturbation theory, many-body perturbation theory, and an exact variational solution of the Boltzmann transport equation I argue that it is now possible to calculate with quantitative accuracy thermal and electrical conductivity fully from first-principles as a function of temperature and doping.In two dimensions, and at variance with typical bulk materials, normal heat-flux conserving processes dominate over Umklapp scattering at room temperature and above. As a result, the phonon gas behaves as an ideal fluid and novel regimes emerge, with collective excitations carrying heat over macroscopic system sizes and Poiseuille and Ziman hydrodynamics, hitherto confined to cryogenic temperatures, characterizing transport at ordinary conditions. In several cases wave-like heat transfer appears in addition to ballistic or diffusive propagation, where second sound may be present at room temperature in graphene, boron nitride, and graphane.Then, I’ll discuss Berry-phase discontinuities in heteroatomic honeycomb lattices, leading to charge reconstructions and the appearance of one-dimensional electron and hole wires, in close analogy with the 2D electron gas emerging at LAO/STO interfaces. Besides their fundamental interest, such wires - either engineered with standard covalent functionalizations or naturally appearing in nanowires, islands, and inversion grain boundaries - could have prospective applications in micro- and nano-electronics and solar-energy harvesting.