相关论文: Quasiparticle and excitonic gaps of one-dimensiona…
Linear carbon-based materials such as polyyne and cumulene oligomers provide a versatile platform for nano-physics and engineering. Direct gap quasi-1D polyyne structures are promising for the observation of strong and unusual excitonic…
Ultra long linear carbon chains of more than 6000 carbon atoms have recently been synthesized within double-walled carbon nanotubes, and they show a promising new route to one--atom--wide semiconductors with a direct band gap. Theoretical…
Quantum Monte Carlo (QMC) is applied to obtain the fundamental (quasiparticle) electronic band gap, $\Delta_f$, of a semiconducting two-dimensional (2D) phosphorene whose optical and electronic properties fill the void between graphene and…
"Metallic" carbon nanotubes exhibit quasiparticle gaps when isolated from a screening environment. The gap-opening mechanism is expected to be of electronic origin, but the precise nature is debated. In this work, we show that hybrid…
Recently, the novel system of linear carbon chains inside of double-walled carbon nanotubes has extended the length of $sp^1$ hybridized carbon chains from 44 to thousands of atoms [L. Shi et al., Nat. Mater. 15, 634 (2016)]. The…
The excitonic luminescence of an isolated polydiacetylene polymer chain in its monomer matrix is studied by micro-photoluminescence. These chains behave as perfect 1D excitonic systems with the expected 1/sqrt{E} density of states between 5…
We report diffusion quantum Monte Carlo (DMC) and many-body $GW$ calculations of the electronic band gaps of monolayer and bulk hexagonal boron nitride (hBN). We find the monolayer band gap to be indirect. $GW$ predicts much smaller…
We study the elementary excitations of a model Hamiltonian for the $\pi$-electrons in poly-diacetylene chains. In these materials, the bare band gap is only half the size of the observed single-particle gap and the binding energy of the…
The excitonic luminescence of an isolated polydiacetylene polymer chain in its monomer matrix is studied by micro-photoluminescence. These chains behave as perfect 1D semiconducting wires with the expected 1/$\sqrt{E}$ density of states…
The electronic band structure of V$_2$O$_5$ is calculated using an all-electron quasiparticle self-consistent (QS) $GW$ method, including electron-hole ladder diagrams in the screening of $W$. The optical dielectric function calculated with…
We present the numerically exact ground state energy, effective mass, and isotope exponents of a one-dimensional lattice polaron, valid for any range of electron-phonon interaction, applying a new continuous-time Quantum Monte Carlo (QMC)…
Significant excitonic effects were observed in graphene by measuring its optical conductivity in a broad spectral range including the two-dimensional {\pi}-band saddle-point singularities in the electronic structure. The strong…
Excitonic effects play a particularly important role in the optoelectronic behavior of two-dimensional semiconductors. To facilitate the interpretation of experimental photoabsorption and photoluminescence spectra we provide (i)…
Highly luminescent isolated polydiacetylene (PDA) chains in a new diacetylene crystal are studied. The diacetylene crystal structure and theoretical calculations suggest that the chains are not planar and more strongly twisted than any…
Dielectric screening is greatly important to an accurate calculation of the exciton binding energies in two-dimensional materials. In this work, we calculate the dielectric function and 2D polarizability of multilayer (up to three)…
We develop an ab initio framework that captures the impact of electron-electron and electron-hole interactions on phonon properties. This enables the inclusion of excitonic effects in the optical phonon dispersions and lifetimes of…
Excitons in monolayer transition-metal dichalcogenides (TMDs) have garnered significant attention because of their large binding energies due to weakly screened Coulomb interaction, and direct bandgap at the K/K$^\prime$ point in the…
We demonstrated the potential of the fractional dimensional approach to understand exciton parameters in the exemplary atomically thin semiconductor material, a monolayer of WS$_2$. This approach has proved to be successful in finding the…
A newly synthesized layered material C2N was investigated based on many- body perturbation theory using GW plus Bethe-Salpeter equation approach. The electronic band gap was determined to be ranging from 3.75 to 1.89 eV from monolayer to…
The Pariser-Parr-Pople Hamiltonian is used to calculate and identify the nature of the low-lying vertical transition energies of polydiacetylene. The model is solved using the density matrix renormalisation group method for a fixed…