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Berry phase in strained InSb whiskers
摘要： Strain influence on the longitudinal magnetoresistance for the n-type conductivity InSb whiskers doped by Sn to concentrations 6·1016–6·1017 сm–3 were studied at temperatures from 4.2 to 50 K and magnetic field up to 10 T. The Shubnikov–de Haas oscillations at low temperatures were revealed in the strained and unstrained samples with all range doping concentration. Some peaks of the longitudinal magnetoresistance split as a doublet in the InSb whiskers with doping concentration in the vicinity to metal-insulator transition. Taking into account peak splitting giant g-factor from 30 to 60 was defined for strained and unstrained samples. The magnetoresistance oscillation period of the InSb whiskers doesn’t differ under strain for all doping concentration, but Fermi energy increases and electron effective mass mс decreases and consists 0.02 m0. Berry phase presence was also revealed in strained n-InSb whiskers that shows their transition under a strain to topological insulator phase.
关键词： Berry phase,topological insulator,strained InSb whiskers,Shubnikov–de Haas oscillations,magnetoresistance
更新于2025-09-23 15:21:21
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-Sn
摘要： Gray tin, also known as α-Sn, can be turned into a three-dimensional topological insulator (3D-TI) by strain and finite-size effects. Such room-temperature 3D-TI is peculiarly interesting for spintronics due to the spin-momentum locking along the Dirac cone (linear dispersion) of the surface states. Angle-resolved photoemission spectroscopy (ARPES) has been used to investigate the dispersion close to the Fermi level in thin (001)-oriented epitaxially strained films of α-Sn for different film thicknesses as well as for different capping layers (Al, AlOx, and MgO). Indeed a proper capping layer is necessary to be able to use α-Sn surface states for spintronic applications. In contrast with free surfaces or surfaces coated with Ag, coating the α-Sn surface with Al or AlOx leads to a drop in the Fermi level below the Dirac point, and an important consequence for electronic transport is the presence of bulk states at the Fermi level. α-Sn films coated by AlOx are studied by electrical magnetotransport: Despite magnetotransport properties of the bulk electronic states of the Γ8 band playing an important role as suggested by ab initio calculations, there is clear evidence of surface states revealed by Shubnikov–de Haas oscillations corresponding to the ARPES observation.
关键词： topological insulator,spin-momentum locking,α-Sn,Shubnikov–de Haas oscillations,Dirac cone,ARPES
更新于2025-09-23 15:21:01
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Transition between Electron Localization and Antilocalization and Manifestation of the Berry Phase in Graphene on a SiC Surface
摘要： It is shown that the transport properties of graphitized silicon carbide are controlled by a surface graphene layer heavily doped with electrons. In weak magnetic fields and at low temperatures, a negative magnetoresistance is observed due to weak localization. A crossover in the magnetoresistance from weak localization to weak antilocalization (the latter is the manifestation of the isospin in graphene) is observed for the first time in samples of this kind at elevated temperatures. A pronounced pattern of Shubnikov–de Haas oscillations is observed in strong magnetic fields (up to 30 T). This pattern demonstrated fourfold carrier spectrum degeneracy due to the double spin and double valley degeneracies. Also, the manifestation of the Berry phase is observed. The effective electron mass is estimated to be m* = 0.08m0, which is characteristic of graphene with a high carrier concentration.
关键词： weak localization,Berry phase,graphene,Shubnikov–de Haas oscillations,silicon carbide,magnetoresistance,weak antilocalization
更新于2025-09-11 14:15:04
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Shubnikov–de Haas oscillations in topological crystalline insulator SnTe(111) epitaxial films
摘要： We report on high-field (up to 30 T) magnetotransport experiments in topological crystalline insulator (111) SnTe epitaxial films. The longitudinal magnetoresistance Rxx exhibits pronounced Shubnikov–de Haas (SdH) oscillation at 4.2 K that persists up to 80 K. The second derivative (?d 2Rxx/dB 2) versus 1/B curve shows a clear beating pattern and the fast Fourier-transform analysis reveals that the SdH oscillations are composed of two close frequencies. As SnTe has elongated bulk Fermi ellipsoids, the 1/ cos θ dependence obtained in the angular evolution of both SdH frequencies is not sufficient to assure conduction via surface states. The Lifshitz-Kosevich fitting of the Rxx oscillatory component confirms the two frequencies and enables us to extract the Berry phase of the charge carriers. The most likely scenario obtained from our analysis is that the beating pattern of these quantum oscillations originates from the Rashba splitting of the bulk longitudinal ellipsoid in SnTe.
关键词： magnetotransport,Rashba splitting,Shubnikov–de Haas oscillations,SnTe,topological crystalline insulator
更新于2025-09-09 09:28:46