부산대학교 도서관

The antiferromagnetic Mott insulator α-Sr2CrO4 possesses multiple spin and orbital ordered phases, but their unique interplay is still relatively unexplored. Here, we used femtosecond optical spectroscopy to study ultrafast spin and orbital ordering dynamics in α-Sr2CrO4 through their non-equilibrium response to photoexcitation. By varying the pump photon energy, we selectively drove inter-site spin hopping between neighboring Cr t2g orbitals and charge transfer-type transitions between oxygen 2p and Cr eg orbitals. The resulting transient reflectivity dynamics revealed temperature-dependent anomalies across the Néel temperature for spin ordering as well as the transition temperatures linked to different types of orbital order. Our results reveal distinct relaxation timescales for spin and orbital orders in α-Sr2CrO4 and provide experimental evidence for the phase transition at TO, possibly related to antiferro-type orbital ordering. Strongly correlated electron systems, such as the chromates, can exhibit a range of unique electronic configurations, the phase diagram of which can become even richer when considering non-equilibrium properties. Here, the authors apply ultrafast optical spectroscopy to α-Sr2CrO4 in order to investigate its spin and orbital ordering dynamics and the changes that occur when varying the pump photon energy. [ABSTRACT FROM AUTHOR]