Nematic Fluctuations in an Orbital Selective Superconductor Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$

Abstract

We present a systematic study of the nematic fluctuations in the iron chalcogenide superconductor Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$ ($0\le x\le 0.53$) using the elastoresistivity technique. Near $x=0$, in proximity to the double-stripe magnetic order of Fe${}_{1+y}$Te, a diverging $B_{1g}$ nematic susceptibility is observed. Upon increasing $x$, despite the absence of magnetic order, the $B_{2g}$ nematic susceptibility increases and becomes dominant, closely following the strength of the $(\pi ,\pi )$ spin fluctuations. Over a wide range of compositions ($0.17\le x\le 0.53$), while the $B_{2g}$ nematic susceptibility follows a Curie temperature dependence (with zero Weiss temperature) at low temperatures, it shows deviations from Curie-Weiss behavior for temperatures higher than $50K$. This is the opposite of what is observed in typical iron pnictides, where Curie-Weiss deviations are seen at low temperatures. We attribute this unusual temperature dependence to a loss of coherence of the $d_{xy}$ orbital, which is supported by our theoretical calculations. Our results highlight the importance of orbital differentiation on the nematic properties of iron-based materials.

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Cited by in corpus (5)

• Pure nematic quantum critical point accompanied by a superconducting dome
• Interaction-induced topological phase transition and Majorana edge states in low-dimensional orbital-selective Mott insulators
• Non-local $d_{xy}$ nematicity and the missing electron pocket in FeSe
• Transfer learning from Hermitian to non-Hermitian quantum many-body physics
• Non-Fermi liquid transport and strong mass enhancement near the nematic quantum critical point in FeSe${}_x$Te${}_{1-x}$ thin films