Unconventional Magnet Junctions Exhibit Tunable Exceptional Points with Unique Symmetries

Unconventional magnets, possessing unique spin textures and zero net magnetisation, are gaining attention as potential components in future spintronic devices. Mohammad Alipourzadeh, Davood Afshar, and Yaser Hajati, all from Shahid Chamran University of Ahvaz, investigate how these magnets respond to external stimuli, specifically magnetic fields and light. Their work demonstrates the emergence of ‘exceptional points’ within junctions combining these unconventional magnets with traditional ferromagnets, and crucially, shows these points can be precisely controlled using light and magnetism. This tunability arises from the fundamental symmetries within these materials, offering a pathway to dynamically manipulate spin-based information and potentially revolutionise the design of advanced spintronic technologies.

Altermagnetism, Spin Textures and 2D Materials

This extensive collection of research papers explores the exciting intersection of 2D materials, spintronics, and a relatively new area of magnetism called altermagnetism. The studies cover a broad range of topics, including the fundamental properties of these materials, how to control their behavior, and potential applications in future technologies. A key focus is understanding how altermagnetism differs from traditional magnetism, and the unique spin arrangements it enables. Much of the research utilizes 2D materials, such as transition metal dichalcogenides, due to their tunable properties and potential for nanoscale devices.

Controlling spin is central to this work, with many papers investigating how spin-orbit coupling influences material properties and how to manipulate spin currents for device applications. A growing area of interest is non-Hermitian physics, which explores systems with gain and loss, leading to novel phenomena and enhanced transport. Researchers are also combining different materials, like 2D materials with superconductors, to create new functionalities. A significant aspect of this research is developing methods to control material properties through strain, electric fields, light, and gate voltages.

The research can be broadly categorized into several areas. Studies explore the fundamental properties of altermagnets, investigating the relationship between crystal structure, electronic structure, and magnetic behavior. Other work focuses on developing spintronic devices based on altermagnets and other 2D materials, examining spin transport phenomena like spin currents and magnetoresistance. Researchers are also creating heterostructures by stacking different 2D materials to engineer new functionalities, and combining 2D materials with superconductors to create hybrid devices. A dedicated area investigates non-Hermitian phenomena in 2D materials, such as exceptional points and enhanced transport.

Finally, many studies focus on controlling material properties using external stimuli like strain, electric fields, and light. Theoretical and computational studies underpin much of this work, providing insights into electronic structure, magnetic properties, and transport phenomena. Combining altermagnetism with non-Hermitian physics is a particularly promising area, potentially leading to enhanced functionalities in spintronic devices. The search for new materials exhibiting altermagnetism or other desirable properties is ongoing, and some of these materials and devices could potentially be used as building blocks for quantum computing applications. In conclusion, this research highlights the exciting progress being made in 2D materials, spintronics, and altermagnetism, paving the way for new materials and devices with transformative applications.

Exceptional Points in Magneto-Optical Hybrid Systems

Researchers investigated unconventional magnetic materials and explored how they interact with light and magnetic fields to create special conditions for electron behavior. These materials possess unusual spin textures and a zero net magnetization, making them promising for future spintronic devices. The team constructed a system combining this unconventional magnet with a conventional ferromagnet, and then carefully manipulated it with both an external magnetic field and circularly polarized light. To achieve this, they employed circularly polarized light, specifically choosing off-resonant frequencies to avoid directly adding energy to the system.

Instead, the light acts as a dynamic control knob, altering the material’s electronic structure without changing its overall energy. This is accomplished through a mathematical technique called the Floquet theorem, which allows researchers to analyze systems that change over time, like those exposed to oscillating light. By carefully tuning the properties of the light and magnetic field, the researchers demonstrated precise control over the location and characteristics of these exceptional points. Their analysis reveals that increasing the intensity of the light reduces the separation between the exceptional points and can even cause them to disappear entirely. This ability to control the number and location of these points opens up possibilities for designing novel spintronic devices where electron behavior can be precisely tailored. Their work highlights the potential of unconventional magnets as platforms for exploring non-Hermitian phenomena and for developing advanced technologies based on manipulating electron spin.

Unconventional Magnetism Controls Exceptional Point Arrangement

Researchers have uncovered a new way to control exceptional points, unique energy states arising in non-Hermitian systems, within a junction combining a ferromagnet and an unconventional magnet exhibiting odd-parity symmetry. These unconventional magnets possess a unique combination of preserved time-reversal symmetry and broken inversion symmetry, leading to distinct properties and potential applications. The study demonstrates that these exceptional points can be precisely manipulated using both external magnetic fields and light. The team discovered that the arrangement of these exceptional points is governed by the inherent characteristics of the unconventional magnet itself, as well as the strength and direction of an applied magnetic field.

Importantly, the application of circularly polarized light introduces a dynamic element, allowing for real-time control over the location and characteristics of these points through a process known as Floquet engineering. This light-based control offers a level of tunability not previously observed in similar systems, enabling researchers to shift, tilt, merge, or even eliminate these exceptional points as desired. Analysis of spin projections and the overlap of quantum states confirms these observations, revealing that combining magnetic field and light control produces effects exceeding what either method achieves alone. This synergistic control unlocks possibilities for advanced spintronic devices, including highly sensitive sensors with dynamically reconfigurable properties and the potential for inducing novel topological phase transitions. The findings establish unconventional magnets as promising platforms for developing light-controlled quantum materials with precisely engineered exceptional points, paving the way for future quantum technologies. This research builds upon the growing field of non-Hermitian physics, where exceptional points, previously considered mathematical curiosities, are now recognized as key features enabling exotic phenomena inaccessible in traditional systems.

UPM Junctions Reveal Tunable Exceptional Points

This research investigates unconventional magnetic materials, known as UPMs, in conjunction with a ferromagnetic material, to explore non-Hermitian physics and the emergence of exceptional points. The study demonstrates that these junctions exhibit exceptional points, which are sensitive to the properties of the UPM itself. Notably, the characteristics of these exceptional points differ from those found in other types of magnetic materials, a distinction arising from the unique symmetries present in UPMs. The researchers found that both an applied magnetic field and circularly polarized light can modify the location and properties of these exceptional points in a momentum-dependent manner, causing shifts, tilts, mergers, or even annihilation. While both external stimuli reshape the exceptional point structure, they operate through distinct mechanisms; light induces a global renormalization, allowing for dynamic control, whereas the magnetic field selectively alters orientation-dependent terms without the same tunability.