Sajna Hameed

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Emergent phases in quantum materials arise from a delicate interplay between lattice, spin, orbital, and electronic degrees of freedom. A central challenge is to control this balance cleanly and reversibly, without introducing chemical disorder. In this talk, I show that uniaxial strain acts as a powerful symmetry-breaking tuning parameter that stabilizes emergent phases across a wide range of systems, from spin-orbit-coupled magnets to quantum paraelectrics. I first discuss strain control of magnetism in the layered spin-orbit-coupled Mott insulator Sr2IrO4, where less than one percent uniaxial strain drives multiple magnetic phase transitions. In situ Raman and resonant x-ray scattering under controlled strain reveal how lattice distortions reshape spin-orbital wavefunctions and interlayer exchange interactions, underscoring the key role of spin-lattice coupling in stabilizing distinct magnetic ground states. I then turn to the incipient ferroelectric and dilute superconductor SrTiO3, where uniaxial strain tunes a paraelectric-ferroelectric quantum phase transition and enhances the superconducting transition temperature. Combining strain with Raman and neutron scattering, we demonstrate access to quantum ferroelectric fluctuations and directly reveal the connection between incipient ferroelectricity and superconductivity in SrTiO3 [1,2].
Together, these case studies establish uniaxial strain as a universal, disorder-free knob for engineering and reversibly controlling emergent phases in quantum materials.

[1] S. Hameed*, D. Pelc* et al., Nat. Materials 21, 54 (2022)
[2] I. Khayr*, N. Somun*, S. Hameed* et al., arXiv:2511.10623 (2025)

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Max Planck Institute for Solid State - Stuttgart
PH2
Contact: Erwann Bocquillon / Matteo Cacco