CsFe₂As₂ is an iron-based superconductor with T_c ~ 2.3 K and a large Sommerfeld coefficient of 180 mJ / mol K, indicating strong electronic correlations at low temperature [1]. In addition, CsFe₂As₂ shows a coherence-incoherence crossover, reminiscent of heavy fermion systems [2,3]. In this contribution, using transport and x-ray diffraction measurements, we demonstrate that in-plane biaxial tension strain, applied by gluing the sample to a rigid substrate with a large mismatch in thermal expansivity, can modify the low-temperature electronic correlations as well as the coherence-incoherence crossover temperature in this material.

[1] F. Hardy et al., Phys. Rev. B 94, 205113 (2016)
[2] F. Hardy et al., Phys. Rev. Lett. 111, 027002 (2013)
[3] Y. P. Wu et al., Phys. Rev. Lett 116, 147001 (2016)