Infrared spectroscopy of Bi2Te2Se

Aleshchenko, Yu. A.; Muratov, A. V.; Павлова, В. В.; Selivanov, Yu. G.; Chizhevskii, E. G.

doi:10.1134/s0021364014040031

Cited by 7 publications

(8 citation statements)

References 17 publications

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“…A series of Sr x Bi 2 Se 3 samples with nominal Sr content of x=0.10, 0.15 and 0.20 were prepared using modified Bridgman method [25]. High purity elemental Bi, Se (99.999%) and Sr (99.95%) in the desired molar ratio were loaded in quartz ampoules inside inert atmosphere glove box.…”

Section: Samplesmentioning

confidence: 99%

Structural distortion behind the nematic superconductivity in Sr_xBi₂Se₃

et al. 2018

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An archetypical layered topological insulator Bi 2 Se 3 becomes superconductive upon doping with Sr, Nb or Cu. Superconducting properties of these materials in the presence of in-plane magnetic field demonstrate spontaneous symmetry breaking: 180 • -rotation symmetry of superconductivity versus 120 • -rotation symmetry of the crystal. Such behavior brilliantly confirms nematic topological superconductivity. To what extent this nematicity is due to superconducting pairing in these materials, rather than due to crystal structure distortions? This question remains unanswered, because so far no visible deviations from the 3-fold crystal symmetry were resolved in these materials. To address this question we grow high quality single crystals of Sr x Bi 2 Se 3 , perform detailed x-ray diffraction and magnetotransport studies and reveal that the observed superconducting nematicity direction correlates with the direction of small structural distortions in these samples (∼0.02% elongation in one crystallographic direction). Additional anisotropy comes from orientation of the crystallite axes. 2-fold symmetry of magnetoresistance observed in the most uniform crystals well above the critical temperature demonstrates that these structural distortions are nevertheless strong enough. Our data in combination with strong sample-to-sample variation of the superconductive anisotropy parameter are indicative for significance of the structural factor in the apparent nematic superconductivity in Sr x Bi 2 Se 3 .

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Section: Samplesmentioning

confidence: 99%

Structural distortion behind the nematic superconductivity in Sr_xBi₂Se₃

et al. 2018

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“…To convert BEP signals into atomic fluxes, Sr flux rate was determined from SrSe reference film thicknesses measured at (0 0 2) XRD reflection oscillations and film deposition time. A series of Sr x Bi 2 Se 3 bulk crystals with nominal Sr content of x=0, 0.01, 0.037 and 0.15 were prepared using modified Bridgeman method [8,30]. To compare properties of thin films and bulk crystals, within this paper we define nominal composition x as a molar fraction of dopant x times 100%(below we will give nominal x in percentage).…”

Section: Growth Techniquementioning

confidence: 99%

“…Thin films with different Sr composition x and thicknesses of 20-50 nm were obtained by the described approach. Immediately after the growth, the film on the substrate was cooled down to the room temperature and, in .037 and 0.15 were prepared using modified Bridgeman method [8,30]. To compare properties of thin films and bulk crystals, within this paper we define nominal composition x as a molar fraction of dopant x times 100%(below we will give nominal x in percentage).…”

Section: Growth and Structural Characterization Techniques Growth Tec...mentioning

confidence: 99%

Effect of Sr doping on structure, morphology, and transport properties of Bi2Se3 epitaxial thin films

Volosheniuk

Selivanov

Bryzgalov

et al. 2019

Journal of Applied Physics

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We report molecular beam epitaxy growth of Sr-doped Bi 2 Se 3 films on (111) BaF 2 substrate, aimed to realize unusual superconducting properties inherent to Sr x Bi 2 Se 3 single crystals. Despite wide range of the compositions, we do not achieve superconductivity. To explore the reason for that we study structural, morphological and electronic properties of the films and compare them to the corresponding properties of the single crystals. The dependence of the c-lattice constant in the films on Sr content appears to be more than an order of magnitude stronger than in the crystals. Correspondingly, all other properties also differ substantially, indicating that Sr atoms get different positions in lattices. We argue that these structural discrepancies come from essential differences in growth conditions. Our research calls for more detailed structural studies and novel growth approaches for design of superconducting Sr x Bi 2 Se 3 thin films.PACS numbers:

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“…In Bi 2 Te 3 , an unconventional decrease of N eff by up to a factor of 2 has been observed between 5 K and 300 K [54,56,57]. For compensated Bi 2 Te 2 Se with N eff ≈ 10 19 cm −3 , a non-monotonic behavior of N eff with a minimum in the range of 50 K to 150 K was reported [51]. However, N eff in Bi 2 Te 2 Se changes by less than 10 % between 5 K and 50 K and by about 20 % between 50 K and 300 K, whereas we find a drastic change by more than a factor of 10 in BiSbTeSe 2 , see Fig.…”

Section: Puddlesmentioning

confidence: 94%

“…The optical properties of Bi 2 Te 3 , Bi 2 Se 3 , and of solid solutions thereof were investigated intensively already half a century ago [41][42][43][44][45] in view of their favorable thermoelectric properties [46,47]. Recently, optical data were reported for single crystals of Bi 2 Te 2 Se and Bi 2−x Sb x Te 3−y Se y showing reduced carrier density [48][49][50][51][52]. However, the bulk carrier dynamics at very low densities were not addressed in detail.…”

Section: Introductionmentioning

confidence: 99%

Revealing puddles of electrons and holes in compensated topological insulators

Borgwardt,

Lux,

Vergara

et al. 2015

Preprint

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Three-dimensional topological insulators harbour metallic surface states with exotic properties. In transport or optics, these properties are typically masked by defect-induced bulk carriers. Compensation of donors and acceptors reduces the carrier density, but the bulk resistivity remains disappointingly small. We show that measurements of the optical conductivity in BiSbTeSe2 pinpoint the presence of electron-hole puddles in the bulk at low temperatures, which is essential for understanding DC bulk transport. The puddles arise from large fluctuations of the Coulomb potential of donors and acceptors, even in the case of full compensation. Surprisingly, the number of carriers appearing within puddles drops rapidly with increasing temperature and almost vanishes around 40 K. Monte Carlo simulations show that a highly non-linear screening effect arising from thermally activated carriers destroys the puddles at a temperature scale set by the Coulomb interaction between neighbouring dopants, explaining the experimental observation semi-quantitatively. This mechanism remains valid if donors and acceptors do not compensate perfectly.

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Infrared spectroscopy of Bi2Te2Se

Cited by 7 publications

References 17 publications

Structural distortion behind the nematic superconductivity in Sr_xBi₂Se₃

Structural distortion behind the nematic superconductivity in Sr_xBi₂Se₃

Effect of Sr doping on structure, morphology, and transport properties of Bi2Se3 epitaxial thin films

Revealing puddles of electrons and holes in compensated topological insulators

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Infrared spectroscopy of Bi2Te2Se

Cited by 7 publications

References 17 publications

Structural distortion behind the nematic superconductivity in Sr x Bi2Se3

Structural distortion behind the nematic superconductivity in Sr x Bi2Se3

Effect of Sr doping on structure, morphology, and transport properties of Bi2Se3 epitaxial thin films

Revealing puddles of electrons and holes in compensated topological insulators

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Product

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Structural distortion behind the nematic superconductivity in Sr_xBi₂Se₃

Structural distortion behind the nematic superconductivity in Sr_xBi₂Se₃