Two-Dimensional Surface Topological Nanolayers and Dirac Fermions in Single Crystals of the Diluted Magnetic Semiconductor (Cd1−x−yZnxMny)3As2 (x + y = 0.3)

Abstract

Features in the transverse magnetoresistance of single-crystalline diluted magnetic semiconductors of a (Cd1–x–yZnxMny)3As2 system with x + y = 0.3 have been found and analyzed in detail. Two groups of samples have been examined. The samples of the first group were thermally annealed for a long time, whereas the samples of the second group were not thermally annealed. The Shubnikov–de Haas (SdH) oscillations were observed for both groups of the samples within a 4.2 ÷ 30 K temperature range and under transverse magnetic field sweeping from 0 up to 11 T. The value of a phase shift, according to the SdH oscillations, was found to be a characteristic of the Berry phase existing in all the samples, except the unannealed sample with y = 0.08. Thickness of 2D surface topological nanolayers for all the samples was estimated. The thickness substantially depended on Mn concentration. The experimental dependence of reduced cyclotron mass on the Fermi wave vector, extracted from the SdH oscillations for the samples with different doping levels, is in satisfactory agreement with the predicted theoretical linear dependence. The existence of the Dirac fermions in all the samples studied (except the unannealed sample with y = 0.08) can be concluded from this result.

Linear dispersion of Dirac fermions in (Cd1–x–yZnxMny)3As2, х+y = 0.2, у = 0.02, 0.04, 0.06, 0.08 solid solutions

“…As can be seen from figure 5, presented experimental data in [15,16,[26][27][28][29][30] and obtained data in this work corresponded to a linear theoretical dependence (straight line), which indicated the existence of massless Dirac fermions.…”

“…The observation of Shubnikov-de Haas (SdH) oscillations while investigating the magnetoresistance of CZMA single crystals allowed us to define the effective mass of charge carriers and compare the Shubnikov, n Sh , and Hall, n h , charge carrier concentrations. In CZMA single crystals, this ratio was close to unity, which indirectly indicated the quality of the studied single crystals [9][10][11][14][15][16].…”

“…CZMA solid solutions has the potential to become extremely useful in the development of electronic devices using twodimensional electron gas [12,13]. For the effective use in electronic appliances, it is essential to determine the characteristics of charge carriers not only as it was done in [10,11], but also taking into account topological properties, notably in recent works devoted to these materials [9,[14][15][16].…”

“…However, to provide a full understanding of the properties of a two-dimensional electron gas in a 3D topological material, we have to know such characteristics as the concentration of charge carriers in the surface 2D layer, n 2D , relaxation time, τ, carrier velocity on the Fermi surface, v f , effective 2D-mobility m , D 2 the dependence of the reduced cyclotron mass m c /m 0 , on the Fermi wave vector k F , which determines the kinetic properties of the electron system and allows to calculate the Fermi energy, carrier velocity, density of localized states, as well as the effective g-factor, which characterizes Zeeman splitting of charge-carrier states in a magnetic field. These characteristics were obtained from Shubnikov-de Haas measurements by SdH oscillations in a magnetic field [14][15][16]. As shown in [15,16], the SdH oscillations are particularly suitable for properties study of a topological insulator and the Berry phase in a 2D conducting channel, which does not depend on the direction of the magnetic field with respect to the vector of the current density flowing through the sample.…”

“…These characteristics were obtained from Shubnikov-de Haas measurements by SdH oscillations in a magnetic field [14][15][16]. As shown in [15,16], the SdH oscillations are particularly suitable for properties study of a topological insulator and the Berry phase in a 2D conducting channel, which does not depend on the direction of the magnetic field with respect to the vector of the current density flowing through the sample.…”