Fractional Quantum Hall Effect in a Diluted Magnetic Semiconductor

TL;DR

This paper reports the observation of the fractional quantum Hall effect in a diluted magnetic semiconductor, revealing how magnetic impurities and tunable Zeeman splitting influence fractional quantum states.

Contribution

It demonstrates the fractional quantum Hall effect in Cd(1-x)Mn(x)Te and models the effects of magnetic impurities on composite fermion Landau levels.

Findings

Observation of fractional quantum Hall effect in a magnetic semiconductor

Unconventional behavior of fractional gaps with in-plane magnetic field

Quantitative modeling of gap opening and closing at specific filling factors

Abstract

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.