Anisotropy and size effects in Bi1-xSbx semiconductor wires in a magnetic field

Albina A Nikolaeva,Ivan А Popov,Pavel P Bodiul,Leonid A Konopko,Tito Е Huber,Gheorghe Para

doi:10.53081/mjps.2021.20-2.01

Albina A Nikolaeva, Ivan А Popov + Show 4 more

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https://doi.org/10.53081/mjps.2021.20-2.01

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Abstract

The electron transport and longitudinal and transverse magnetoresistance (MR) of glass-insulated Bi0.92Sb0.08 single-crystal wires with diameters of 180 nm to 2.2 μm and the (1011) orientation along the wire axis have been studied. The wires have been prepared by liquid-phase casting. It has been first found that the energy gap ΔE increases by a factor of 4 with a decrease in wire diameter d due to the manifestation of the quantum size effect, which can occur under conditions of a linear energy–momentum dispersion law characteristic of both the gapless state and the surface states in topological insulators (TIs). It has been revealed that, in strong magnetic fields at low temperatures, a semiconductor–semimetal transition occurs, which is evident as an anomalous decrease in the transverse MR anisotropy and the appearance of a metallic temperature dependence of resistance at T < 100 K. It has been found that the effect of negative MR, the appearance of an anomalous maximum in the longitudinal MR, and the dependence of Hmax ~ d-1 at 4.2 K is a manifestation of the classical MacDonald–Chambers size effect. The calculated value of the component of the Fermi momentum perpendicular to the magnetic induction vector H is 2 times higher than the value for pure bismuth wires. The features of the manifestation of the quantum size effect in Bi0.92Sb0.08 wires, semiconductor–semimetal electronic transitions induced by a magnetic field, and a decrease in the transverse MR anisotropy indicate the occurrence of new effects in low-dimensional structures based on semiconductor wire TIs, which require new scientific approaches and applications.

Highlights

IntroductionBi1 хSbх alloys have attracted the attention of researchers due to the fact that, on the one hand, these alloys can be used as a model material, which is extremely sensitive to stoichiometry, magnetic field, size, temperature, and deformations [1–3], and, on the other hand, these alloys are a promising material for thermoelectric energy converters at temperatures of 200 K, millivolt electronics, and infrared applications [4, 5]
For many years, Bi1 хSbх alloys have attracted the attention of researchers due to the fact that, on the one hand, these alloys can be used as a model material, which is extremely sensitive to stoichiometry, magnetic field, size, temperature, and deformations [1–3], and, on the other hand, these alloys are a promising material for thermoelectric energy converters at temperatures of 200 K, millivolt electronics, and infrared applications [4, 5].Bi1 хSbх alloys are representatives of the semimetal–semiconductor band inversion semiconductor system
This anomalous change in the transverse MR anisotropy is a consequence of the semiconductor–semimetal electronic transition associated with the overlapping of the electron La and hole T4,5 extremes in strong magnetic fields [21, 22]

Summary

Introduction

Bi1 хSbх alloys have attracted the attention of researchers due to the fact that, on the one hand, these alloys can be used as a model material, which is extremely sensitive to stoichiometry, magnetic field, size, temperature, and deformations [1–3], and, on the other hand, these alloys are a promising material for thermoelectric energy converters at temperatures of 200 K, millivolt electronics, and infrared applications [4, 5]. The authors of [14, 15] discuss the possibility of using TIs in next-generation electronic and spintronic devices; the predicted increase in thermoelectric figure of merit in lowdimensional TI structures makes it possible to use them to design alternative energy sources and miniature thermocooling devices. In this manuscript, results of studying the electron transport and the manifestation of classical and quantum size effects in the longitudinal and transverse magnetoresistance (MR) of TI semiconductor wires of Bi0.92Sb0.08 alloys in a wide range of temperatures, magnetic fields, and wire diameters are described

Experimental

Results and Discussion

Temperature dependence of resistance

Magnetoresistance

Conclusions