Chemical and magnetic impurity effects on electronic properties of semiconductor quantum wires

Abstract

We present a theoretical study of electronic states in magnetic and nonmagnetic semiconductor quantum wires. The effects of chemical and magnetic disorder at paramagnetic temperatures are investigated in single-site coherent potential approximation. It is shown that the nonmagnetic impurity shifts the band of carriers and suppresses the van Hove singularities of the local density of states (LDOS) depending on the value of impurity concentration. The magnetic impurity, however, broadens the band which depends on the strength of exchange coupling, and in the high impurity concentration, the van Hove singularities in the LDOS can completely disappear and the curves become smooth.

Electronic and optical spectra in a diluted magnetic semiconductor multilayer

“…Therefore, by choosing the above values for ε M and IS we can model the system to show gap opening in the electronic states due to the doping of M atoms into the AB structure. Since the system consists of five atomic layers, one can expect five energy subbands in the band structure of the system [27]. Each subband is attributed to one of the atomic layers.…”

“…Therefore, the type of disorder in our model is considered to be diagonal and accordingly, the off-diagonal disorder is outside of the scope of the present study. The random site energy u A,M r,n is assumed to be u A r,n and u M r,n with probabilities 1 − x and x when the lattice site (r, n) is occupied by the A and M atoms, respectively [21,26,27]. For A and M sites we have:…”

“…In this study, instead of taking the quantum fluctuation of the localized spin of the magnetic ions into account, the classical spin approximation (i.e. S → ∞) is used, while IS is a constant parameter [26,27]. According to the CPA, a disordered alloy can be replaced by an effective periodic medium in which the potential of all sites is replaced by an energy-dependent coherent potential, except one site which is denoted by impurity [24].…”

“…A direct consequence of this replacement is the fact that the effective scattering of a carrier at the impurity site is zero, on average [24]. The matrix elements of the effective Green's function are calculated by the following Dyson equation [27]:…”

Tunnel magnetoresistance of a CnBN (n = 58 and 68) molecular junction

“…Girard et al found that both of the non-magnetic B and C adatoms in a metallic (5,5) single-walled carbon nanotube cause zero-bias conductance that is highly dependent on the spin states of the conduction electrons [32]. Chemical and magnetic impurity effects on the electronic properties of semiconductor quantum wires were investigated by Safarzadeh [33]. Moreover, studies have shown that the localized states of the impurity can change the spin-polarized conduction in the presence of a gate voltage or applied bias [34,35].…”