The researchers use a hybrid of lasers to control huge currents at super-fast speeds

The flow of matter, from macroscopic currents to microscopic currents of electric charge, underpins much of modern infrastructure. In search of breakthroughs in energy efficiency, data storage capacity and processing speed, scientists are looking for ways to control the flow of quantum aspects of matter, such as the "spin" of an electron - its magnetic moment - or its "valley." States, "a new quantum aspect of matter found in many two-dimensional materials. A team of researchers at the Max Born Institute in Berlin has recently discovered a way to induce and control spin and valley flow in super-fast time with specially designed laser pulses, providing a new perspective on the ongoing search for next-generation information technology.

Ultrafine laser control of the fundamental quantum degrees of freedom of matter represents the special fundamental challenge of building the information technology of the future, beyond the semiconductor electronics that define our current era. The two most promising quantum degrees of freedom in this regard are electron spin and the "valley index," which is the degree of freedom generated from two-dimensional materials related to the momentum of quasiparticles. Spintronics and valley electronics have many potential advantages over traditional electronic devices in terms of data processing speed and energy efficiency. However, while the spin excitation is affected by the dynamic loss of properties due to spin induced precession, the valley wave function represents a "bit data" whose stability is only threatened by intermittent scattering, which is a controllable feature of sample mass. As a result, Valleytronics offers a potentially powerful platform beyond traditional electronics.

The charge-controlled state of circularly polarized light is now well established, and the famous "spin valley locking" of transition metal chalcogenides originates from the valley's selective response to circularly polarized light. This can be thought of as caused by the selection rules for magnetic quantum numbers involving d orbitals, which include deviated edge states. Although circularly polarized light excites valley charge, it does not produce valley current. This occurs when for every quasi pulse in the valley the K-valley is excited by the counterpart -k valley is also excited: thus Bloch velocities cancel each other out and there is no net valley current.

Therefore, full control of light-induced valley flow and its amplitude and direction requires going beyond the spin valley locking paradigm of circularly polarized light. Thus, the generation of excited valley states to produce clear valley and spin currents must involve the destruction of local currents.

In addition to quantum excitation of encoded data bits, the core of any future valley or spintronics technology will be the control and creation of valley and spin currents. However, while there has been a focus on the task of tuning optical morphology on ultrafast time scales to selectively excite valley quasi particles, the precise creation and control of valley flows and spin currents - essential for any future valley electronics technology - remains beyond. Ultrafast optical control area. In a recent study published in Science Advances, a team of researchers at the Max Born Institute in Berlin showed how a hybrid laser pulse combining two polarizations can fully control the current caused by an ultrafine laser.

The charge-controlled state of circularly polarized light is now well established, and the famous "spin valley locking" of transition metal chalcogenides originates from the valley's selective response to circularly polarized light. This can be thought of as caused by the selection rules for magnetic quantum numbers involving d orbitals, which include deviated edge states. Although circularly polarized light excites valley charge, it does not produce valley current. This condition manifests itself in every quasi-impulse in the valley

Source: Laser Net