Anti-ferromagnetic axion isolators are an exotic state of matter that was proposed decades ago, but remains experimentally elusive to this day.
New Delhi: Scientists have discovered that electrically tuning magnetism in certain exotic states of matter can lead to striking optical effects that are useful in certain optical devices.
It has been discovered that upon application of an electric field, electrons in the upper and lower layers of a special type of magnetic insulator called anti-ferromagnetic axion insulator spontaneously deflect in opposite directions.
“This property called Layer Hall Effect allows the magnetism of these materials to be effectively controlled by an external electric field leading to electrical tuning of magnetism with important applications in next-generation magnetic and optical devices,” a statement released by the Department of Science and Technology (DST) said Thursday.
“About the exotic state of matter”
Anti-ferromagnetic axion insulators are an exotic state of matter that was proposed decades ago, but remains experimentally elusive to this day.
The manganese-bismuth telluride (MnBi2Te4) series of compounds has emerged as a promising class of anti-ferromagnetic axion insulator, and scientists are exploring its unique properties to use them in more innovative ways.
A team from IIT Kanpur came across the “Layer Hall Effect” property in devices a few nanometers thick made of layers of MnBi2Te4.
“What is the Hall Effect”
The Hall effect refers to the generation of a transverse voltage in response to an electric field. It occurs in materials in the presence of a magnetic field. More recently, it has been shown to occur even in the absence of a magnetic field, stemming from the “geometry” of the movement of electrons in a crystalline solid, according to an article published in the journal Nature.
The IIT Kanpur team led by Amit Agarwal experimentally observed a new type of Hall effect called Layer Hall Effect in which the top and bottom layers of the device generate cross current in opposite directions, which is made possible by a geometric property of the electron. in crystals.
“Field of Axion”
Moreover, the IIT Kanpur team observed that the magnetic state of MnBi2Te4 can be effectively switched by a coupled magnetic and electric field known as an axionic field.
This study, supported by the Science Engineering and Research Board (SERB) and the Department of Science and Technology (DST), opens the field to explore more exotic optical and transport effects in MnBi2Te4 using axionic electromagnetic coupling, adds the press release.
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