Palestrante
Descrição
Two-electron atoms, such as the negatively charged hydrogen ion (H-) and helium atom (He) have played an important role in the development of theoretical physics in the last century.The quantum state of two paired electrons in such an atom is different in its nature from the single-electron state because of the strong electron correlation. It is a formidable task to determine the correlation energy accurately in this two-electron system. For instance, very recently, using high-precision variational calculations Estienne et al.(1) determined the critical nuclear charge $Z_c$ = 0.911028224 077255 73(4) which is the minimum charge required to bind two electrons.When a two-electron atom is confined in a two-dimensional (2D) system, the electron correlation is significantly enhanced and new effects appear. A two-electron atom in 2Dis not only a model system for studying the negatively charged donor impurity center and charged exciton confined in semiconductor quantum wells, but such electron pair states in a 2D lattice may also form an electron-pair energy band (2)being possibly related to the mechanism of the unconventional superconductivity.Though two-electron atoms in 2D system have been extensively studied, we notice thata systematic investigation on the correlation effects in this system has not been reported.In this work, we have performed a theoretical study on the ground state of the two-electron atoms in 2D. The calculation is aimed to obtain the ground-state energy within reasonable precision but with the wavefunction being of as simple expression as possible. We start with a three-parameter variational function (3), and it is then extended to a superposition with N terms. In order to obtain the electron correlation energy, calculation within the Hartree-Fock approximation has also been done. The electron correlation energy of the two-electron atoms in 2D is obtained as a function of the nuclear charge Z, and an quantitative comparison with that in a 3D system is presented. We find that the minimum nuclear charge required to bind a two-electron atom in 2D is much smaller being $Z_c$ ≈ 0.809, whereas the value of this critical charge increases to 1.18 within the Hartree-Fock approximation without electron correlation.We have also assumed that the effective interactions between the constituents of a two-electron atom are given by Thomas-Fermi potentials and investigated the screening effects in this system. The obtained results are compared with our quantum Monte Carlo calculations for a two-electron atom embedded in a 2D electron gas.
Referências
1 ESTIENNE, C. S. et al. Erratum: Critical nuclear charge for two electron atoms. Physical Review Letters,v. 113,n.3, p.039902, 2014.
2 HAI, G. Q. et al.Electron pairing: from metastable electron pair tobipolaron. Journal of Physics Communications, v. 2,n.3, p.035017, 2018.
3 HOGAASEN, H.; RICHARD, J.M.; SORBA, P. Two-electron atoms, ions, and molecules. American Journal of Physics, v. 78, n.1, p.86, 2010.
| Apresentação do trabalho acadêmico para o público geral | Não |
|---|---|
| Subárea | Física Atômica e Molecular |
