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Tailoring of Electronic Structure and Thermoelectric Properties of a Topological Crystalline Insulator by Chemical Doping
Author(s) -
Roychowdhury Subhajit,
Shenoy U. Sandhya,
Waghmare Umesh V.,
Biswas Kanishka
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201508492
Subject(s) - doping , condensed matter physics , thermoelectric effect , materials science , band gap , topological insulator , electronic structure , crystal (programming language) , crystal structure , mirror symmetry , symmetry breaking , semimetal , crystallography , chemistry , physics , quantum mechanics , computer science , programming language
Topological crystalline insulators (TCIs) are a new quantum state of matter in which linearly dispersed metallic surface states are protected by crystal mirror symmetry. Owing to its vanishingly small bulk band gap, a TCI like Pb 0.6 Sn 0.4 Te has poor thermoelectric properties. Breaking of crystal symmetry can widen the band gap of TCI. While breaking of mirror symmetry in a TCI has been mostly explored by various physical perturbation techniques, chemical doping, which may also alter the electronic structure of TCI by perturbing the local mirror symmetry, has not yet been explored. Herein, we demonstrate that Na doping in Pb 0.6 Sn 0.4 Te locally breaks the crystal symmetry and opens up a bulk electronic band gap, which is confirmed by direct electronic absorption spectroscopy and electronic structure calculations. Na doping in Pb 0.6 Sn 0.4 Te increases p‐type carrier concentration and suppresses the bipolar conduction (by widening the band gap), which collectively gives rise to a promising zT of 1 at 856 K for Pb 0.58 Sn 0.40 Na 0.02 Te. Breaking of crystal symmetry by chemical doping widens the bulk band gap in TCI, which uncovers a route to improve TCI for thermoelectric applications.