Journal
COMMUNICATIONS PHYSICS
Volume 4, Issue 1, Pages -Publisher
NATURE PORTFOLIO
DOI: 10.1038/s42005-021-00591-7
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Funding
- Fapesp [2016/00756-6, 2017/10581-1, 2018/20142-8, 2018/11364-7, 2018/18653-4]
- CNPq, Brazil [308607/2018-0, 304496/2017-0, 409504/2018-1]
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This study investigates the resistive and Raman scattering properties of Co-doped Sr2IrO4 and provides evidence for quantum critical fluctuations in the system.
Iridates provide a fertile ground to investigate correlated electrons in the presence of strong spin-orbit coupling. Bringing these systems to the proximity of a metal-insulator quantum phase transition is a challenge that must be met to access quantum critical fluctuations with charge and spin-orbital degrees of freedom. Here, electrical transport and Raman scattering measurements provide evidence that a metal-insulator quantum critical point is effectively reached in 5% Co-doped Sr2IrO4 with high structural quality. The dc-electrical conductivity shows a linear temperature dependence that is successfully captured by a model involving a Co acceptor level at the Fermi energy that becomes gradually populated at finite temperatures, creating thermally-activated holes in the J(eff)=1/2 lower Hubbard band. The so-formed quantum critical fluctuations are exceptionally heavy and the resulting electronic continuum couples with an optical phonon at all temperatures. The magnetic order and pseudospin-phonon coupling are preserved under the Co doping. This work brings quantum phase transitions, iridates and heavy-fermion physics to the same arena. Due to a combination of strong spin orbit coupling and electron correlations iridates such as Sr2IrO4 exhibit a range of exotic quantum states that can be tuned via their electronic and magnetic properties. Here, the authors investigate the resistive and Raman scattering properties of Co-doped Sr2IrO4 and provide evidence for quantum critical fluctuations in the system.
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