Magnetic-field dependence of low-lying spectra in magnetic quantum rings and dots

In this paper, the magnetic-field dependence of low-lying spectra of a single-electron magnetic quantum ring and dot, formed by inhomogeneous magnetic fields, are calculated using the numerical diagonalization scheme. The effects of on-center acceptor and donor impurities are also considered. In the presence of an acceptor impurity, transitions in the orbital angular momentum, $L$, are found for both the magnetic quantum ring and the magnetic quantum dot when the magnetic field is varied.

Figure 1

Low-lying spectra of a magnetic quantum dot as a function of $1∕a_c^2(\propto B)$, (a) no impurity, (b) acceptor, and (c) donor. Note that all states are labeled by the quantum numbers $(n,l)$ and the states $n=0$, $n=1$, and $n=2$ are denoted by the curved solid, dashed, and dotted lines, respectively. The lowest three Landau levels ($N_r=0$, 1, 2) are denoted by solid straight lines.

Figure 2

Low-lying spectra of a magnetic quantum ring as a function of $1∕a_c^2(\propto B)$, (a) no impurity, (b) acceptor, and (c) donor. The meanings of different line types are similar to those of Fig. 1.

Figure 3

Magnetic moments as a function of $1∕a_c^2(\propto B)$. Note that, for a clear presentation, the magnetic moments for the curves are drawn in different scales.