Researchers create theoretical descriptions of light-induced topological states

z = 0 which are magnified around E = 0. Here, the bands dominated by the s-orbital (p-orbital) component are indicated by a red (blue) solid line. The abscissa axis is measured k l in 1 / d l With l = x, y, z. (a) E (k) at the k . level x −k y at k z = 0 for higher spin ranges. (b) Same as panel (a) but for lower rotation bands. credit: physical audit b (2022). DOI: 10.1103/ PhysRevB.106.085206″ width=”543″ height=”530″/>

Energy dispersion E (k) for up and down spin bands at kz= 0 which are magnified around E = 0. Here, the bands dominated by the s-orbital (p-orbital) component are indicated by a red (blue) solid line. coordinate axis kto It is measured in 1/dto With l = x, y, z. (a) E (k) in kx−ky plane in kz= 0 for higher spin bands. (b) Same as panel (a) but for lower rotation bands. attributed to him: physical review b (2022). DOI: 10.1103/ PhysRevB.106.085206

Topological materials that possess certain symmetries at the atomic level, including topological insulators and topological semimetals, have sparked fascination among many condensed matter scientists because of their complex electronic properties. Now, researchers in Japan have demonstrated that an ordinary semiconductor can be converted into a topological semiconductor by light irradiation. Furthermore, they demonstrated how spin-dependent responses can appear when illuminated with circularly polarized laser light. Posted in physical review bIn this work, this work explores the possibility of creating topological semimetals and demonstrating new physical properties by controlling light, which may open up rich physical frontiers for topological properties.

Most ordinary materials either electrical conductors, such as metals or insulators such as plastics. in contrast, Topological insulators It can show unusual behavior in which electric currents flow along the surface of the sample, but not inside. This characteristic behavior is strongly related to the inherent topological properties of the electronic state. Moreover, a new phase called topological semimetallic provides a new playing field for exploring the role of topology in condensed matter. However, the basic physics of these systems remains to be considered.

Researchers at the University of Tsukuba studied the excitation dynamics of zinc arsenide (Zn .).3as such2) when irradiated with a circular polarization laser. Zinc arsenide is usually thought of as a narrow-gap semiconductor, which means that the electrons are not free to move around on their own but can be easily propelled by energy from an external light source. Under the right conditions, the material can exhibit a special topological state called ‘flucket-well semi-metal’, which is a topological light-coupled quasi-metal. In this case, the electric current They can be carried in the form of quasiparticles called Weyl fermions. Because quasiparticles travel as if they have zero mass and resist scattering, Weyl fermions can easily move through matter.

“Fluoket-Well semi-metals show quite a few rare properties in which they can be used electronic devicesincluding high motion, giant magnetoresistance, and spin-polarized currents,” says author Professor Ken Ichi Hino. In the present work, the researchers demonstrated that when a left-hand circularly polarized continuous wave laser is tuned to a frequency roughly matching the energy gap of the material , the spin electrons and the spin electrons form different phases, a Weyl semi-metal and a narrow-gap insulator. The latter is located near another topological semi-metal called a nodal-line quasi-metal.

“Our exploration of the trans-excitation dynamics of zinc arsenide could deepen the understanding of the physics underlying these materials,” senior author Runnan Zhang says. This fundamental research could also help accelerate the development of light-induced surface magnetization techniques for non-magnetic materials.


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more information:
Runnan Zhang et al, Fluocyt-Weil half-metal generated by an inter-optical resonant transition, physical review b (2022). DOI: 10.1103/ PhysRevB.106.085206

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