Light Transforms Magnetic Material into Exotic ‘Chern Insulator’ State

Researchers have demonstrated that altermagnets exhibit unusual thermoelectric and thermal Hall effects following irradiation with light. Fang Qin from Jiangsu University of Science and Technology, alongside Xiao-Bin Qiang from Southern University of Science and Technology, and colleagues, reveal how elliptically polarised light transforms an altermagnet into a Chern insulator, subsequently inducing these effects. This work is significant because it establishes a novel method for probing both the electronic bandwidth and topological properties of materials via measurements of thermoelectric and thermal Hall conductivities at extremely low temperatures. Specifically, the observed linear temperature dependence and eventual quantisation of these conductivities offer a new pathway for characterising complex quantum states within irradiated altermagnets.

Light-induced topological phase transition in d-wave altermagnets generates anomalous Hall effects

Researchers have demonstrated a pathway to transform a d-wave altermagnet into a Chern insulator using elliptically polarized light, opening possibilities for advanced electronic technologies. This breakthrough centers on manipulating material states with light, specifically inducing a topological phase transition within the altermagnet.
The study details how irradiation with a high-frequency photon beam fundamentally alters the material’s electronic structure, creating conditions for novel thermoelectric and thermal transport properties. Specifically, the research reveals that exposing the d-wave altermagnet to elliptically polarized light generates a gap within its electronic band structure, a crucial step towards realizing the Chern insulating state.

This light-induced transformation activates intrinsic anomalous thermoelectric and thermal Hall effects, previously suppressed in the material. At extremely low temperatures, the thermoelectric Hall coefficient vanishes within this newly formed energy gap, but exhibits distinct peaks and dips at its boundaries, suggesting a sensitivity to the material’s bandwidth.

Further investigation reveals that the low-temperature thermal Hall coefficient becomes quantized in the gapped region. This quantization is a highly specific and measurable topological property, confirming the successful induction of a topologically distinct phase. The ability to control and probe these topological properties with light irradiation establishes a new avenue for designing energy-efficient electronic devices.

This work highlights the potential of light as a powerful tool for controlling material states and accessing novel functionalities. The quantized thermal Hall conductivity serves as a robust signature of the induced topological order, offering a pathway to create materials with tailored thermal transport characteristics. These findings could contribute to the development of next-generation electronic technologies based on topological materials and their unique properties.

Elliptically polarized light from a high-frequency photon beam was utilized to transform a d-wave altermagnet into a Chern insulator. This irradiation played a crucial role in activating intrinsic thermoelectric and thermal Hall responses within the material. Prior to light exposure, the material exhibited metallic behavior.

Light-induced Chern insulator formation and topological phase transition in a d-wave altermagnet

Researchers have demonstrated the transformation of a d-wave altermagnet into a Chern insulator through irradiation with elliptically polarized light. This transition is evidenced by the observation of quantized thermal Hall conductivity, a key indicator of topological order. Specifically, the thermal Hall coefficient becomes quantized in the gapped region of the material’s band structure, signifying a highly specific and measurable topological property induced by the light irradiation.

The study details measurements of intrinsic anomalous thermoelectric and thermal Hall effects in the light-irradiated altermagnet. At extremely low temperatures, the thermoelectric Hall coefficient, normally exhibiting a linear temperature dependence, vanishes within the energy gap between the conduction and valence bands.

Peaks and dips are observed at the boundaries of this gap, suggesting that thermoelectric Hall conductivity can be utilized to probe the material’s bandwidth. Further analysis reveals that the low-temperature thermal Hall coefficient also displays a linear temperature dependence for thermal Hall conductivity, but crucially, it becomes quantized in the gapped region.

This quantization is a direct consequence of the induced topological state and provides a robust signature of the material’s altered electronic structure. The precise value of the thermal Hall coefficient in this gapped region confirms the emergence of a topologically non-trivial state. These findings demonstrate a pathway for light-based control of material states and open possibilities for developing new, energy-efficient electronic technologies based on topological materials. The ability to induce and probe topological properties with light offers a versatile approach to manipulating electronic behavior at the nanoscale, potentially leading to advancements in spintronics and quantum computing.

Light-induced topological phase transition and emergent thermal Hall quantization

Researchers have demonstrated the transformation of a d-wave altermagnet into a Chern insulator through irradiation with elliptically polarized light. This manipulation induces specific thermoelectric and thermal Hall effects within the material, offering a pathway to control material states using light.

Investigations into these effects reveal that the thermoelectric Hall coefficient vanishes within the energy gap between conduction and valence bands, exhibiting peaks and dips at the gap boundaries which can be used to probe the material’s bandwidth. Notably, the thermal Hall coefficient becomes quantized in this gapped region, indicating the emergence of a measurable topological property induced by the light irradiation.

This quantization provides a direct probe of the topological characteristics of the altermagnet. The observed phenomena suggest potential applications in developing energy-efficient electronic technologies based on topological materials, leveraging light as a control mechanism for material properties.

The authors acknowledge that the described behaviour is observed within a specific low-temperature environment and relies on the characteristics of the chosen altermagnet material. Future research could focus on extending these findings to other materials and exploring the potential for manipulating topological states at higher temperatures, potentially broadening the scope of applications for this light-based control method.