Tuning materials properties on demand is at the heart of condensed matter science. Charge transport and magnetism are strongly linked to the overlap of electronic wave functions and can be, thus, manipulated by varying the electronic bandwidth through chemical substitution or physical pressure. Yet, a controlled variation of the symmetry, anisotropy and frustration of transfer integrals and exchange interactions remained inaccessible so far.
Here, we explore Mott insulators subject to strong antiferromagnetic interactions, where geometrical frustration suppresses magnetic order entirely [1,2] or down to very low temperatures T_N << J [3-6]. Utilizing the recent advancements in strain tuning of unconventional superconductors [7,8], we apply uniaxial stress to fine-tune the Mott transition with unprecedented precision in a triangular-lattice compound [2]. Through the slope of the metal-insulator boundary in the temperature-pressure phase diagram we pinpoint the nonmagnetic ground state of the most intensely studied quantum-spin-liquid candidate [1,2]. By applying in situ uniaxial pressure to a clean, well-studied kagome-lattice compound without disorder [3-5], we obtain direct control of antiferromagnetic order within one single crystal [6]. As the applied stress reduces the frustration strength, the transition temperature is enhanced by 10% [6]. Our pioneering endeavors [2,6] demonstrate uniaxial strain as a powerful tool to tune interacting spins on frustrated lattices – towards stabilizing novel, exotic, possibly even quantum entangled spin states.

References
[1] B. Miksch, A. Pustogow, M. Javaheri Rahim, A. A. Bardin, K. Kanoda, J. A. Schlueter, R. Hübner, M. Scheffler, M. Dressel, Science 372, 276-279 (2021)
[2] A. Pustogow, Y. Kawasugi, H. Sakurakoji, N. Tajima, Nat. Commun. 14, 1960 (2023)
[3] P. Puphal, M. Bolte, D. Sheptyakov, A. Pustogow, K. Kliemt, M. Dressel, M. Baenitz, C. Krellner, J. Mater. Chem. C 5, 2629 (2017)
[4] T. Biesner et al., Adv. Quantum Technol. 2022, 2200023 (2022)
[5] D. Chatterjee et al., Phys. Rev. B 107, 125156 (2023)
[6] Jierong Wang, Y.-S. Su, M. Spitaler, K.M. Zoch, C. Krellner, P. Puphal, S.E. Brown, and A. Pustogow, Phys. Rev. Lett. 131, 256501 (2023)
[7] C.W. Hicks et al., Science 344, 283 LP (2014)
[8] A. Chronister et al., npj Quantum Mater. 7, 113 (2022)