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Albina Nikolaeva1 2 Leonid Konopko1 2 Tito Huber3 Krzysztof Rogacki2 Igor Gherghishan1 Oxana Botnari1

1, D.Ghitu IEEN, Chisinau, , Moldova (the Republic of)
2, Institute of Low Temperatures and Structural Research, Wroclaw, , Poland
3, Howard University, Washington, Washington, United States

Toplogical insulators (TI) represent a new quantum state of matter which is characterized by peculiar edge of surface states and expect to observe new physical phenomena that have never been observed in other system.
We report transport studies, Shubnikov-de Haas oscillations (SdH) and thermoelectric properties on Bi2Te3 topological insulator thin layers and wires.
Perfect single crystalline of Bi2Te3 layers with thickness 10- 20 μm were prepared using the mechanical exfoliate method by cleaving thin layer from bulk single crystal Bi2Te3 samples [1]. Bi2Te3 microwires in glass coating with diameter d= 10- 20 μm were prepared by the Ulitovsky- Taylor method [2]. X- ray studies showed that the Bi2Te3 layers were single- crystal and the plane of the layers was perpendicular to the C3 trigonal axis. The microwire core is in general polycrystal consisting of big disoriented single crystal blocks.
From experimental data on SdH oscillations at temperature of 2.1- 4.2 K, cyclotron effective mass, Dingle temperature and the quantum mobility of charge carriers are calculated. The high quantum mobilities mq~13000cm2/V*sec. were determined from SdH oscillations in longitudinal (LM) (H||I) and transverse (H⊥I) magnetic fields (TM) up to 14 T at 2.1 K in layers and are substantially higher than in the bulk.
It was revealed, that the value of phase shift SdH oscillations has made 0,5 both in parallel, and in perpendicular magnetic fields in Bi2Te3 layers and wires. It is known, that phase shift is connected with Berry’s phase which is the integrated characteristic of orbit cyclotron curvature and the electron dispersion and is characteristic surface state.
The unique surface properties, transport, thermoelectric and thermopower measurements observed in these objects (layers and wires TI) contributes the new complex approach to thermoelectric device (thermogenerators and thermocoolers) fabrication.
This work was supported by Institutional project 15.817.02.09A.

[1] D. Teweldebrhan, V. Goyal and A. Balandin, Nano Lett., 10(4), 1209–1218 (2010).
[2] A. Nikolaeva, D. Gitsu, L. Konopko, M. Graf, and T. Huber, Phys. Rev. B, 77, 075332 (2008).

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