Pressure induced local structural changes and its implication on the electronic properties: studies on few selected layered systems

Start Date
20-02-2018 10:00
End Date
20-02-2018 11:00
Room 500 - 501, Central Building
Speaker's name
Boby Joseph
Speaker's institute
Elettra Sincrotrone Trieste, Italy
Contact name
Eva Jahn
Host name
S. Pascarelli
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In a pioneering work using EXAFS, Mikkelsen and Boyce demonstrated the existence of atomic scale random alloying leading to the occurrence of distinct local bond distances than what is expected from a virtual crystal approximation in Ga1-xInxAs [1]. Following the discovery of superconductivity in the FeSe1-xTex system, our EXAFS investigations  revealed a similar atomic scale random alloying scenario leading to two distinct chalcogen heights above the Fe square lattice [1] implying the importance to go beyond the average structural description to understand these multiband systems. Pressure is found to enhance the superconducting critical temperature in FeSe0.5Te0.5 until the occurrence of a tetragonal to monoclinic phase at 2.7 GPa, where our EXAFS results revealed distinct changes in the local bond distances revealing the structure property correlations [3].  XAS measurements on a  similar layered system, IrTe2 having an Ir triangular lattice, where doping  is found to induce superconductivity, revealed the  importance of the Ir 3d and Te 5p orbitals in driving structural dynamics [4]. Pressure dependent EXAFS and XANES spectra at 300 and 100 K were employed to further explore the details of structural phase transitions [5].  Very recently using high pressure Raman and XRD studies, we revealed  two isostructural transitions in  1T-TiTe2, yet another layered transition metal dichalcogenide [6], where first principle studies predicted the occurrence of pressure dependent topologically trivial and non-trivial quantum phase transitions [7]. This system under uniaxial pressure is found become superconducting (transition temperature 5.3 K at 12 GPa), where curiously a pressure quenchable superconducting state is detected [8], motivating systematic pressure dependent low temperature XAS investigations.


[1] J. C. Mikkelsen Jr. and J. B. Boyce, Phys. Rev. Lett.  49, 1412 (1982). [2] B. Joseph, A. Iadecola, A. Puri et al., Phys. Rev. B 82, 020502 (2010); M. Y. Hacisalihoglu, E. Paris, B. Joseph et al., Phys. Chem. Chem. Phys. 17, 18131 (2015). [3] M. Bendele, Z. Guguchia, F. von Rohr, et al., Phys. Rev. B 90, 174505 (2014). [4] B. Joseph, M. Bendele, L. Simonelli, et al., Phys. Rev. B 88, 224109 (2013); B. Joseph, E. Paris, D. F. Mulato-Gomez et al., J. Phys.: Condens. Matter 26, 375702 (2014). [5] E. Paris, B. Joseph, A. Iadecola, et al., Phys. Rev. B 93, 134109 (2016). [6] V. Rajaji, U. Dutta, P.C. Sreeparvathy, et al., Phys. Rev. B 97, 085107 (2018). [7] Q. Zhang, Y. Cheng, U. Schwingenschlogl, Phys. Rev. B 88, 155317 (2013). [8] U. Dutta, P.S. Malavi, S. Sahoo, B. Joseph, S. Karmakar, Phys. Rev. B (to appear)

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