Electronic structure and relaxation dynamics in a superconducting topological material

Madhab Neupane; Yukiaki Ishida; Raman Sankar; Jian-Xin Zhu; Daniel S. Sanchez; Ilya Belopolski; Su-Yang Xu; Nasser Alidoust; Shik Shin; Fangcheng Chou; M. Zahid Hasan; Tomasz Durakiewicz

doi:10.1038/srep22557

arXiv · 1511.00278

Electronic structure and relaxation dynamics in a superconducting topological material

Madhab Neupane·Yukiaki Ishida·Raman Sankar·Jian-Xin Zhu·Daniel S. Sanchez·Ilya Belopolski·Su-Yang Xu·Nasser Alidoust·Shik Shin·Fangcheng Chou·M. Zahid Hasan·Tomasz Durakiewicz

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Abstract

Topological superconductors host new states of quantum matter which show a pairing gap in the bulk and gapless surface states providing a platform to realize Majorana fermions. Recently, alkaline-earth metal Sr intercalated Bi2Se3 has been reported to show superconductivity with a Tc ~ 3 K and a large shielding fraction. Here we report systematic normal state electronic structure studies of Sr0.06Bi2Se3 (Tc ~ 2.5 K) by performing photoemission spectroscopy. Using angle-resolved photoemission spectroscopy (ARPES), we observe a quantum well confined two-dimensional (2D) state coexisting with a topological surface state in Sr0.06Bi2Se3. Furthermore, our time-resolved ARPES reveals the relaxation dynamics showing different decay mechanism between the excited topological surface states and the two-dimensional states. Our experimental observation is understood by considering the intra-band scattering for topological surface states and an additional electron phonon scattering for the 2D states, which is responsible for the superconductivity. Our first-principles calculations agree with the more effective scattering and a shorter lifetime of the 2D states. Our results will be helpful in understanding low temperature superconducting states of these topological materials.

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Madhab Neupane, Yukiaki Ishida, Raman Sankar, Jian-Xin Zhu, Daniel S. Sanchez, Ilya Belopolski, Su-Yang Xu, Nasser Alidoust, Shik Shin, Fangcheng Chou, M. Zahid Hasan, Tomasz Durakiewicz. 2015-11-01. Electronic structure and relaxation dynamics in a superconducting topological material. https://doi.org/10.1038/srep22557

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