Raman fingerprints for competing magnetic and electronic phases in Ti doped Ca3Ru2O7

The strongly correlated polar metal Ca3Ru2O7 displays a rich phase diagram with Ti doping arising from the confluence of multiple magnetic and electronic phases. With increasing Ti concentration, the ground state changes from a quasi 2-dimensional metal to a Mott insulating state at 5% Ti doping, showing weakly localized behavior at intermediate doping levels. This is accompanied by a change in the low temperature magnetic structure from an AFM-b to G-AFM arrangement. Recent work on the parent compound identified a change in the phonon spectra across the simultaneous metal-insulator and spin-reorientation transition [1]. A natural question that arises is whether the ground state phonon spectra is dominated by the effect of the electronic phase or the magnetic structure. Using temperature dependent polarized Raman spectroscopy and density functional theory, we find that the Raman modes are strongly coupled to the electronic phase with little sensitivity to the magnetic structure in Ca3(Ru1−xTix)2O7. In addition, we identify changes in the low energy electronic structure as evidenced by the symmetry resolved electronic background extracted from the Raman spectra. This study demonstrates the importance of the phonon modes in modulating the electronic phase transitions in strongly correlated systems.

[1] Wang, Huaiyu, et al. “Strong electron-phonon coupling driven pseudogap modulation and density-wave fluctuations in a correlated polar metal.” Nature communications 14.1 (2023): 5769.