Significance A new class of heterostructures consisting of layered transition metal dichalcogenide components can be designed and built by van der Waals (vdW) stacking of individual monolayers into functional multilayer structures. Nonetheless, the optoelectronic properties of this new type of vdW heterostructure are unknown. Here, we investigate artificial semiconductor heterostructures built from single-layer WSe 2 and MoS 2 . We observe spatially direct absorption but spatially indirect emission in this heterostructure, with strong interlayer coupling of charge carriers. The coupling at the hetero-interface can be readily tuned by inserting hexagonal BN dielectric layers into the vdW gap. The generic nature of this interlayer coupling is expected to yield a new family of semiconductor heterostructures having tunable optoelectronic properties through customized composite layers.

We propose a cellular version of dynamical-mean field theory which gives a natural generalization of its original single-site construction and is formulated in different sets of variables. We show how non-orthogonality of the tight-binding basis sets enters the problem and prove that the resulting equations lead to manifestly causal self energies.Comment: RevTex, 4 pages, 1 embedded figur

We investigate the thermoelectric response of correlated electron systems near the density driven Mott transition using the dynamical mean field theory.Comment: 4 pages, 2 embedded figure

We report the first angle-resolved photoemission measurement of the wave-vector dependent plasmon satellite structure of a three-dimensional solid, crystalline silicon. In sharp contrast to nanomaterials, which typically exhibit strongly wave-vector dependent, low-energy plasmons, the large plasmon energy of silicon facilitates the search for a plasmaron state consisting of resonantly bound holes and plasmons and its distinction from a weakly interacting plasmon-hole pair. Employing a first-principles theory, which is based on a cumulant expansion of the one-electron Green's function and contains significant electron correlation effects, we obtain good agreement with the measured photoemission spectrum for the wave-vector dependent dispersion of the satellite feature, but without observing the existence of plasmarons in the calculations. Introduction.-Within the contemporary view of condensed matter physics[1] in the Fermi liquid paradigm, the electronic structure of materials is described in terms of a quasiparticle picture, where particle-like excitations (such as those measured in transport or photoemission experiments) in an otherwise strongly interacting electron system are characterized by weakly interacting quasi-electrons and quasi-holes, consisting of the bare particles and a surrounding screening cloud of electronhole pairs and collective excitations. One example of such collective excitations are plasmons, quantized charge density oscillations resulting from the long-range nature of the Coulomb interaction. Both the energy and the dispersion relation of plasmons depend sensitively on the dimensionality of the material. In three-dimensional materials, the energy required to excite a plasmon is typically multiple electron volts, but in two-and one-dimensional systems, such as doped graphene [2] or metallic carbon nanotubes [3], plasmons can be gapless excitations with strong wave-vector dependence and vanishing energy in the zero wave-vector limit.