Seminarium Oddziału Badań Magnetyków
Microsoft Teams
Quantum oscillations in magnetotransport of bismuth chalcogenides
dr inż. Maciej Chrobak
Wydział Fizyki i Informatyki Stosowanej Akademii Górniczo-Hutniczej w Krakowie
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Streszczenie:
Electronic structure of topological insulators is characterized by simultaneous occurrence of gapped bulk states and massless Dirac fermions at the surface. The latter are protected by time-reversal symmetry, which leads to lack of backscattering of massless fermions on impurities. It results in high efficiency of spin pumping as well as anomalous magnetotransport, both being very promising from application point of view (e.g. in modern electronic devices).
In this talk I will present systematic studies of magnetoresistance in Bi2Se3 and Bi2Te3 single crystals, undoped and doped with magnetic and nonmagnetic metals. The measurements were carried out by four-probe technique or by Van der Pauw method with a lock-in amplifier using 3He/4He dry dilution refrigerator "Triton" combined with the "Nanonis Tramea" system for quantum transport measurements. The measurements were performed at temperature range from 100 mK to 30 K in magnetic field up to 14 T. The results reveal that low level doping has an influence on the frequency and amplitude of Shubnikov-de Haas oscillations.
For Bi2Se3 single crystals the Berry phase obtained from Landau level fan diagram (derived from the Shubnikov-de Haas oscillations) indicates that a small amount of magnetic dopant (1 % Fe) does not affect the non-trivial topology, preserving the non-zero Berry phase. On the other hand, charge dopant (2 % Mg) modifies the topology of electronic structure leading to changes of the Berry phase.
In opposite to Bi2Se3 magnetic dopants in Bi2Te3 single crystals affect the topology and quantum oscillations are not visible up to 14 T.
This work was financially supported by National Science Centre, Poland (grant no: 2015/17/B/ST3/00128).
