Evidence for Charging Effects in CdTe/CdMgTe Quantum Point Contacts

Here we report on fabrication and low temperature magnetotransport measurements of quantum point contacts patterned from a novel two-dimensional electron system - CdTe/CdMgTe modulation doped heterostructure. From the temperature and bias dependence we ascribe the reported data to evidence for a weakly bound state which is naturally formed inside a CdTe quantum constrictions due to charging effects. We argue that the spontaneous introduction of an open dot is responsible for the replacement of flat conductance plateaus by quasi-periodic resonances with amplitude less than 2e^{2}/h, as found in our system. Additionally, below 1 K a pattern of weaker conductance peaks, superimposed upon wider resonances, is also observed.Comment: 4 pages, 4 figure

Mapping of quantum well eigenstates with semimagnetic probes

We present results of transmission measurements on CdTe quantum wells with thin semimagnetic CdMnTe probe layers embedded in various positions along the growth axis. The presence of the probes allow us to map the probability density functions by two independent methods: analyzing the exciton energy position and the exciton Zeeman splitting. We apply both approaches to map the first three quantum well eigenstates and we find that both of them yield equally accurate results.Comment: Accepted for publication in Physical Review

Fractional Quantum Hall Effect in a Diluted Magnetic Semiconductor

We report the observation of the fractional quantum Hall effect in the lowest Landau level of a two-dimensional electron system (2DES), residing in the diluted magnetic semiconductor Cd(1-x)Mn(x)Te. The presence of magnetic impurities results in a giant Zeeman splitting leading to an unusual ordering of composite fermion Landau levels. In experiment, this results in an unconventional opening and closing of fractional gaps around filling factor v = 3/2 as a function of an in-plane magnetic field, i.e. of the Zeeman energy. By including the s-d exchange energy into the composite Landau level spectrum the opening and closing of the gap at filling factor 5/3 can be modeled quantitatively. The widely tunable spin-splitting in a diluted magnetic 2DES provides a novel means to manipulate fractional states

Mutanase from Paenibacillus sp. MP-1 produced inductively by fungal α-1,3-glucan and its potential for the degradation of mutan and Streptococcus mutans biofilm

Laetiporus sulphureus is a source of α-1,3-glucan that can substitute for the commercially-unavailable streptococcal mutan used to induce microbial mutanases. The water-insoluble fraction of its fruiting bodies from 0.15 to 0.2% (w/v) induced mutanase activity in Paenibacillus sp. MP-1 at 0.35 μ ml−1. The mutanase extensively hydrolyzed streptococcal mutan, giving 23% of saccharification, and 83% of solubilization of glucan after 6 h. It also degraded α-1,3-polymers of biofilms, formed in vitro by Streptococcus mutans, even after only 3 min of contact