Prof. Cedomir Petrovic [上海前瞻物质科学研究院]

Title: Disorder in FeSe1−xSx (0 ≤ x ≤ 1) superconducting crystals

Language:  English presentation

Time: Beijing, 3:00 - 4:00 PM, Thursday, April 11, 2024

Place:  Onsite：Conference room A417, HPSTAR (Beijing)             Online:  Tencent Meeting: https://meeting.tencent.com/dm/OSHno3Mf0PTI  Meeting ID: 905-663-653

Host:  Dr. Yang Ding

Abstract:

Connections among crystal chemistry, disorder and critical temperature Tc have been at the forefront of superconductivity, one of the most widely studied phenomena in physics, chemistry and materials science alike. In Fe-based superconductors Tc correlates with the average anion height above the Fe plane, i.e. with the geometry of the FeAs4 or FeCh4 (Ch = Te, Se, S) tetrahedron. By synthesizing FeSe1−xSx (0 ≤ x ≤ 1) single crystal alloys with atomic defects we find that their Tc is not correlated with the anion height of other Fe superconductors. Instead, changes in Tc(x) and tetragonal-to-orthorombic (nematic) transition Ts(x) on cooling are correlated with Bragg plane and Fe vibrations disorder in direction orthogonal to Fe planes and thereby induced scattering rates (1/τ)(x) [1,2]. The disorder stems from deformed Fe(Se,S)4 tetrahedra with different Fe-Se and Fe-S bond distances. Moreover, high-temperature metallic resistivity in the region of strong disorder exceeds Mott limit and provides an example of the strong violation of Matthiesen’s rule and Mooij law which is known to be a dominant when adding moderate disorder past the Drude/Matthiassen’s regime in all materials [2]. Scattering mechanism of Mott limit-exceeding resistivity is unrelated to phonons and arises for strong Se/S atom disorder in tetrahedral surrounding of Fe. Observations point to intricate connection between nanostructure details and unconventional scattering mechanism, possibly related to charge-nematic or magnetic spin fluctuations [2,3].
References[1] Aifeng Wang et al., Inorg. Chem. 61, 11036 (2022).[2] Aifeng Wang et al., Nano Lett. 22, 6900 (2022).[3] Yu Liu et al., Nanoscale Horizons 10, 59 (2023).