Unveiling the Intriguing World of Non-Reciprocal Magnetism: A Theoretical Framework Defying Newton's Third Law
Photoinduced non-reciprocal magnetism is a fascinating phenomenon that challenges our understanding of physics. Researchers from Japan have discovered a theoretical framework that predicts the emergence of non-reciprocal interactions in solids, effectively breaking Newton's third law. This groundbreaking work opens up new possibilities in the field of non-equilibrium materials science and could lead to innovative applications in light-controlled quantum materials.
In the realm of physics, equilibrium systems adhere to the principle of action and reaction, as described by Newton's third law. However, in non-equilibrium systems, such as biological or active matter, non-reciprocal interactions become prevalent. These interactions defy the traditional law of action and reaction, and researchers have long wondered if they could be harnessed in solid-state electronic systems.
A team of researchers, led by Associate Professor Ryo Hanai from the Department of Physics at the Institute of Science Tokyo, Japan, in collaboration with Associate Professor Daiki Ootsuki from Okayama University and Assistant Professor Rina Tazai from Kyoto University, has provided an affirmative answer. They proposed a theoretical method to induce non-reciprocal interactions in solid-state systems using light, marking a significant advancement in the field.
The team's study reveals a general approach to transforming ordinary reciprocal spin interactions into non-reciprocal ones using light. As an example, they demonstrate how the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction, a well-known phenomenon in magnetic metals, can acquire a non-reciprocal character when exposed to light at a specific frequency. This frequency selectively opens a decay channel for certain spins, while leaving others off-resonant, resulting in a unique magnetic behavior.
The researchers developed a dissipation-engineering scheme that utilizes light to selectively activate decay channels in magnetic metals. These metals possess localized spins and freely moving conduction electrons, leading to spin-exchange coupling. By activating decay channels, the team created an imbalance in energy injection between different spins, resulting in non-reciprocal magnetic interactions.
When applied to a bilayer ferromagnetic system, the dissipation-engineering scheme predicted a non-equilibrium phase transition known as a non-reciprocal phase transition. In this transition, one magnetic layer attempts to align with the other, while the other tends to anti-align, leading to a spontaneous and continuous rotation of magnetization. This 'chiral' phase is characterized by persistent chase-and-run dynamics, a unique feature of broken action-reaction symmetry.
The required light intensity for inducing non-reciprocal phase transitions is estimated to be within the reach of current experimental capabilities. This discovery not only provides a new tool for controlling quantum materials with light but also bridges concepts from active matter and condensed matter physics. It has the potential to be applied to Mott insulating phases of strongly correlated electrons, multi-band superconductivity, and optical phonon-mediated superconductivity.
Furthermore, this research could enable the development of new types of spintronic devices and frequency-tunable oscillators. It sheds light on the applicability of non-reciprocal interactions to solid-state systems and their potential implications for next-generation technologies. The team's findings were published in the journal Nature Communications, marking a significant milestone in the field.
This study invites further exploration and discussion. Are there other ways to induce non-reciprocal interactions in solid-state systems? How might this research impact the development of quantum technologies? The researchers encourage readers to share their thoughts and interpretations in the comments section, fostering a community of curious minds.
