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A coherent phonon-induced hidden quadrupolar ordered state in Ca2RuO4
Honglie Ning1,2, Omar Mehio1,2, Xinwei Li1,2
1Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA, USA.
Nature Communications
|December 12, 2023
Summary
Ultrafast lasers can reveal hidden electronic states in materials. This study demonstrates inducing a forbidden quadrupolar ordered state in Ca2RuO4 using phonon excitation, offering a new way to control exotic matter phases.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Materials
Background:
- Ultrafast laser excitation can transiently access hidden electronic states in materials, beyond thermal equilibrium.
- Previous studies revealed charge density waves, ferroelectric, magnetic, and charge-orbital ordered states.
- Exotic hidden states with higher multipolar ordering are challenging to manipulate and detect optically.
Purpose of the Study:
- To demonstrate a method for inducing a dynamical transition to a thermally forbidden spin-orbit entangled quadrupolar ordered state.
- To explore the control and detection of hidden multipolar ordering using light-matter interactions.
- To uncover novel electronic phases in strongly correlated materials like Ca2RuO4.
Main Methods:
- Coherent excitation of a specific phonon mode coupled to the quadrupolar order parameter in Ca2RuO4.
- Utilizing ultrafast laser pulses for dynamical state manipulation.
- Employing probe photon energy-resolved coherent phonon spectroscopy for detection.
Main Results:
- Successfully induced a dynamical transition from a thermally allowed to a forbidden quadrupolar ordered state.
- Observed anomalies in phonon behavior dependent on temperature, pump fluence, and probe energy, confirming the transition.
- Demonstrated the strong coupling between the excited phonon and the quadrupolar order parameter.
Conclusions:
- Introduced a general pathway to uncover and control hidden multipolar ordered states.
- Showcased the potential of phonon excitation for manipulating exotic electronic phases on ultrashort timescales.
- Opened new avenues for exploring novel quantum states in correlated materials.
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