Year: 2026
Type: preprint
Abstract: The magnetic behavior of Ca$_2$RuO$_4$ represents a unique puzzle due to the interplay of strong electronic correlations, magneto-elastic interactions, and large spin-orbit coupling. At low temperatures, an anomalous Mott insulating state emerges, characterized by a complex antiferromagnetic order with a collective amplitude excitation of the magnetic moment which has been discussed in analogy with the Higgs mode. We report here evidence of a magnetic first-order phase transition driven by an out-of-plane magnetic field along the crystallographic $c$-axis of Ca$_2$RuO$_4$. Raman measurements in magnetic field reveal the emergence of mode of magnetic origin and a concomitant modification of the coupling between a phonon and the Higgs amplitude mode. Both the Raman features are characterized by a non-reciprocal hysteresis in magnetic field. Surprisingly, the observed phase transition does not affect the Raman scattering from the in-plane magnons, indicating that the dipolar antiferromagnetic order is preserved. This is consistent with the onset of a new quadrupolar field-controlled state, whose fluctuations structure can trigger an hybridization between the lattice and the magnetic Higgs mode resulting in the observed Raman features.
Source: arXiv (Cornell University)
Authors: Jarc, Giacomo, Tartaglia, Giovanni, Gabriele, Francesco, Forte, Filomena, Guarino, Anita, Montanaro, Angela, Rigoni, Enrico Maria, Khatiwada, Nitesh, Lincetto, Costanza, Bartolini, Gabriele, Mastropasqua, Antonio, Mathengattil, Shahla Yasmin, Malvestuto, Marco, Rehman, Muhammad Waqee Ur, Fittipaldi, Rosalba, Deisenhofer, Joachim, Tsirlin, Alexander A., Vecchione, Antonio, Cuoco, Mario, Fausti, Daniele
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7212029269