Flat-band excitonic states in Kagome lattice on semiconductor surfaces
نویسندگان
چکیده
Recent surface techniques to fabricate and arrange quantum wires on the semiconductor surface have enabled to synthesize the artificial two-dimensional lattice systems such as square and triangle lattices. For example, C. Albrecht et al. produced a square lattice by arranging InAs wires on GaInAs (001) surface and showed that a butterfly energy spectra is seen in the case of applying the magnetic field. [1] Among various lattices, a Kagome lattice is located at the special position because of the appearance of complete flat bands in the electronic spectra. [2,3] Since the density of states of such flat bands is macroscopically large and the electronic correlation remarkably works when the half of a flat band is occupied by electrons through the application of the gate voltage, the surface ferromagnetism is predicted for nonmagnetic semiconductor surfaces [2,3] and the experimental challenges to realize a Kagome lattice is now in progress. In this view, one can also expect that a Kagome lattice shows an exotic optical properties, which have never been studied yet. In this paper, we investigated the excitonic properties of the Kagome lattice. Most remarkable finding is that the exciton binding energy on the Kagome lattice is extremely large; larger than that in one-dimensional system. By changing the dimensionality of the lattice system, it is shown that such large binding energy originates from the flatness of the lowest-conduction and highest-valence bands in the Kagome lattice. Moreover, by calculating the binding energies of charged exciton and biexciton, we show that the excitons are easy to form charged exciton. We expect that the present results will give useful information for the optical detection of the flat bands.
منابع مشابه
Carbon kagome lattice and orbital-frustration-induced metal-insulator transition for optoelectronics.
A three-dimensional elemental carbon kagome lattice, made of only fourfold-coordinated carbon atoms, is proposed based on first-principles calculations. Despite the existence of 60° bond angles in the triangle rings, widely perceived to be energetically unfavorable, the carbon kagome lattice is found to display exceptional stability comparable to that of C(60). The system allows us to study the...
متن کاملsd(2) Graphene: Kagome band in a hexagonal lattice.
Graphene, made of sp^{2} hybridized carbon, is characterized with a Dirac band, representative of its underlying 2D hexagonal lattice. The fundamental understanding of graphene has recently spurred a surge in the search for 2D topological quantum phases in solid-state materials. Here, we propose a new form of 2D material, consisting of sd^{2} hybridized transition metal atoms in hexagonal latti...
متن کاملA bird’s eye view on the flat and conic band world of the honeycomb and Kagome lattices: towards an understanding of 2D metal-organic frameworks electronic structure
We present a thorough tight-binding analysis of the band structure of a wide variety of lattices belonging to the class of honeycomb and Kagome systems including several mixed forms combining both lattices. The band structure of these systems are made of a combination of dispersive and flat bands. The dispersive bands possess Dirac cones (linear dispersion) at the six corners (K points) of the ...
متن کاملJ ul 2 00 6 The mobility of dual vortices in honeycomb , square , triangular , Kagome and dice lattices
It was known that by a duality transformation, interacting bosons at filling factor f = p/q hopping on a lattice can be mapped to interacting vortices hopping on the dual lattice subject to a fluctuating dual ” magnetic field” whose average strength through a dual plaquette is equal to the boson density f = p/q. So the kinetic term of the vortices is the same as the Hofstadter problem of electr...
متن کامل