Sum-rule constraints on the surface state conductance of topological insulators

We report the Drude oscillator strength D and the magnitude of the bulk band gap E_{g} of the epitaxially grown, topological insulator (Bi,Sb)_{2}Te_{3}. The magnitude of E_{g}, in conjunction with the model independent f-sum rule, allows us to establish an upper bound for the magnitude of D expecte...

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Bibliographic Details
Published in:Physical review letters 2015-09, Vol.115 (11), p.116804-116804, Article 116804
Main Authors: Post, K W, Chapler, B C, Liu, M K, Wu, J S, Stinson, H T, Goldflam, M D, Richardella, A R, Lee, J S, Reijnders, A A, Burch, K S, Fogler, M M, Samarth, N, Basov, D N
Format: Article
Language:English
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Summary:We report the Drude oscillator strength D and the magnitude of the bulk band gap E_{g} of the epitaxially grown, topological insulator (Bi,Sb)_{2}Te_{3}. The magnitude of E_{g}, in conjunction with the model independent f-sum rule, allows us to establish an upper bound for the magnitude of D expected in a typical Dirac-like system composed of linear bands. The experimentally observed D is found to be at or below this theoretical upper bound, demonstrating the effectiveness of alloying in eliminating bulk charge carriers. Moreover, direct comparison of the measured D to magnetoresistance measurements of the same sample supports assignment of the observed low-energy conduction to topological surface states.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.115.116804