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@PhDThesis{Okazaki::InPrMa,
               author = "Okazaki, Anderson Kenji",
                title = "Investiga{\c{c}}{\~a}o das propriedades de magnetotransporte no 
                         isolante topol{\'o}gico cristalino telureto de chumbo e estanho",
               school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
              address = "S{\~a}o Jos{\'e} dos Campos",
                month = "2019-06-03",
             keywords = "telureto de chumbo e estanho, epitaxia de feixe molecular, 
                         isolante topol{\'o}gico cristalino, magnetorresist{\^e}ncia 
                         longitudinal, oscila{\c{c}}{\~o}es de Shubnikov-de Haas, lead 
                         tin telluride, molecular beam epitaxy, topological crystalline 
                         insulator, longitudinal magnetoresistance, Shubnikov-de Haas 
                         oscillations.",
             abstract = "O composto semicondutor Pb1-xSnxTe foi recentemente revelado como 
                         um isolante topol{\'o}gico cristalino que apresenta uma 
                         transi{\c{c}}{\~a}o de isolante trivial para topol{\'o}gico 
                         acima da composi{\c{c}}{\~a}o cr{\'{\i}}tica xc de Sn onde 
                         ocorre a invers{\~a}o de bandas. Este trabalho visa investigar as 
                         propriedades de magnetotransporte em toda a faixa de 
                         composi{\c{c}}{\~a}o da liga em intensos campos magn{\'e}ticos 
                         B de at{\'e} 30 T. Para tanto, filmes monocristalinos de 
                         Pb1-xSnxTe (0 \≤ x \≤ 1) foram crescidos por 
                         epitaxia de feixe molecular sobre substratos de BaF2 (111). A 
                         caracteriza{\c{c}}{\~a}o el{\'e}trica a baixo campo (B = 0,7 T) 
                         e a 12 K mostrou que a densidade de portadores do tipo-p e a 
                         mobilidade Hall variam de 2,6  1017 a 1,9  1020 cm-3 e de 23 000 
                         a 1 500 cm/Vs, respectivamente, assim que a 
                         composi{\c{c}}{\~a}o da liga muda do PbTe para o SnTe. As 
                         medi{\c{c}}{\~o}es da resist{\^e}ncia longitudinal, Rxx, 
                         at{\'e} B = 30 T revelam oscila{\c{c}}{\~o}es qu{\^a}nticas de 
                         Shubnikov-de Haas (SdH) para filmes com x \≥ 0,70. As 
                         oscila{\c{c}}{\~o}es SdH mais intensas ocorrem no SnTe e, por 
                         isso, permitem uma an{\'a}lise detalhada nesse material. A 
                         segunda derivada (-dRxx/dB) versus 1/B apresenta um claro 
                         padr{\~a}o de batimento a 4,2 K que persisti at{\'e} 80 K. A 
                         an{\'a}lise da transformada r{\'a}pida de Fourier (FFT) revela 
                         que as oscila{\c{c}}{\~o}es s{\~a}o compostas de duas 
                         componentes com frequ{\^e}ncias pr{\'o}ximas. A massa 
                         ciclotr{\^o}nica correspondente a cada frequ{\^e}ncia foi 
                         determinada pelo amortecimento t{\'e}rmico da amplitude FFT e 
                         concorda com os valores publicados na literatura para o SnTe. Como 
                         o SnTe tem elipsoides de Fermi alongados, o comportamento 
                         1/costheta, observado na depend{\^e}ncia angular de ambas as 
                         frequ{\^e}ncias SdH, n{\~a}o {\'e} suficiente para garantir a 
                         condu{\c{c}}{\~a}o pelos estados de superf{\'{\i}}cie. O 
                         ajuste das componentes oscilat{\'o}rias de Rxx {\`a} 
                         equa{\c{c}}{\~a}o de Lifshitz-Kosevich confirmam as duas 
                         frequ{\^e}ncias, o que permiti extrair as fases de Berry dos 
                         portadores de carga. As an{\'a}lises demonstram que as 
                         componentes oscilat{\'o}rias surgem da divis{\~a}o do elipsoide 
                         longitudinal do SnTe volum{\'e}trico devido ao efeito Rashba de 
                         polariza{\c{c}}{\~a}o de spin que coexiste com a fase 
                         topol{\'o}gica. Devido a uma grande magnetorresist{\^e}ncia de 
                         fundo, as amostras com concentra{\c{c}}{\~a}o de Sn abaixo de 
                         0,70 n{\~a}o s{\~a}o capazes de produzir oscila{\c{c}}{\~o}es 
                         intensas o suficiente para possibilitar a an{\'a}lise do 
                         transporte de cargas. Por{\'e}m, o amortecimento t{\'e}rmico das 
                         oscila{\c{c}}{\~o}es nas amostras com x \≥ 0,70 permite 
                         observar a diminui{\c{c}}{\~a}o da massa efetiva 
                         ciclotr{\^o}nica com o aumento de x, que {\'e} uma 
                         evid{\^e}ncia da mudan{\c{c}}a da superf{\'{\i}}cie de Fermi 
                         em fun{\c{c}}{\~a}o da composi{\c{c}}{\~a}o de Sn na liga. A 
                         aplica{\c{c}}{\~a}o do campo magn{\'e}tico simultaneamente 
                         paralelo {\`a} superf{\'{\i}}cie da amostra e {\`a} 
                         dire{\c{c}}{\~a}o da corrente, revelou que a 
                         magnetorresist{\^e}ncia longitudinal negativa n{\~a}o {\'e} uma 
                         caracter{\'{\i}}stica exclusiva dos isolantes topol{\'o}gicos, 
                         mas que pode ser uma propriedade geral de metais e semicondutores 
                         afetada pela distor{\c{c}}{\~a}o das linhas de campo 
                         el{\'e}trico. No Pb1-xSnxTe, essa altera{\c{c}}{\~a}o das 
                         linhas equipotenciais {\'e} blindada pela fase ferroel{\'e}trica 
                         que tem a temperatura de transi{\c{c}}{\~a}o diminu{\'{\i}}da 
                         com a redu{\c{c}}{\~a}o de Sn na liga. ABSTRACT: The 
                         semiconductor compound Pb1-xSnxTe has recently been revealed as a 
                         topological crystalline insulator, which presents a transition 
                         from trivial to topological insulator above a critical Sn 
                         composition, xc, where the band inversion occurs. This work aims 
                         the investigation of the Pb1-xSnxTe magnetotransport properties 
                         covering the entire composition range at intense magnetic field B 
                         up to 30 T. For this purpose, monocrystalline Pb1-xSnxTe films (0 
                         \≤ x \≤ 1) were grown by molecular beam epitaxy on 
                         (111) BaF2 substrates. The electrical characterization at low 
                         field (B = 0.7 T) and 12 K showed that the p-type carrier density 
                         and Hall mobility varied from 2.6  1017 to 1.9  1020 cm-3 and 
                         from 23,000 to 1,500 cm/Vs, respectively, as the Sn content 
                         increased from PbTe to SnTe. The longitudinal resistance, Rxx, 
                         measurements up to B = 30 T revealed Shubnikov-de Haas (SdH) 
                         quantum oscillations for films with x \≥ 0.70. The most 
                         intense SdH oscillations occurred for SnTe that allowed a detailed 
                         analysis for this material. Second derivative (-dRxx/dB) versus 
                         1/B exhibited a clear beating pattern at 4.2 K, which persisted 
                         until 80 K. From fast Fourier transform (FFT) analysis was 
                         demonstrated that the oscillations are composed by two components 
                         with close frequencies. The cyclotron mass correspondent to each 
                         frequency was determined by the thermal damping of FFT amplitude 
                         and agree with the values published in literature for SnTe. As 
                         SnTe has elongated Fermi ellipsoids, the 1/costheta dependence 
                         obtained in the angular evolution of both SdH frequencies is not 
                         enough to ensure conduction via surface states. The 
                         Lifshitz-Kosevich fitting of the Rxx oscillatory components 
                         confirmed the two frequencies and allowed to extract the Berrys 
                         phases of the carriers. The analyses show that the oscillatory 
                         components originate from SnTe bulk longitudinal ellipsoid spin 
                         splitting due to Rashba effect, which coexists with the 
                         topological phase. Due to a large background magnetoresistance, 
                         the samples with Sn content lower than 0.70 were not able to 
                         produce oscillations with enough intensity to allow the carriers 
                         transport analyses. However, the thermal damping of the 
                         oscillations in the samples with x \≥ 0.70 permitted to 
                         observe the effective cyclotron mass reduction with increasing x, 
                         which is an evidence of the Fermi surface alteration as the Sn 
                         content changes. The negative longitudinal magnetoresistance 
                         observed with the magnetic field applied simultaneously parallel 
                         to the sample surface and to the current direction is not an 
                         exclusive feature of topological insulators but can be a general 
                         property of metals and semiconductors affected by the electric 
                         field lines distortion. In Pb1-xSnxTe, this modification of the 
                         equipotential lines is shielded by ferroelectric phase, whose 
                         transition temperature diminishes with the Sn content reduction in 
                         the alloy.",
            committee = "Rappl, Paulo Henrique de Oliveira (presidente/orientador) and 
                         Abramof, Eduardo (orientador) and Corat, Evaldo Jos{\'e} and 
                         Barreto, Patr{\'{\i}}cia Regina Pereira and Peres, Marcelos Lima 
                         and Teles, Lara K{\"u}hl",
         englishtitle = "Magnetotransport properties investigation of the topological 
                         crystalline insulator lead tin telluride",
             language = "pt",
                pages = "91",
                  ibi = "8JMKD3MGP3W34R/3TH8PAL",
                  url = "http://urlib.net/rep/8JMKD3MGP3W34R/3TH8PAL",
           targetfile = "publicacao.pdf",
        urlaccessdate = "27 nov. 2020"
}


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