Researchers at IIT Bombay developed a simple method that uses a single linearly polarized laser pulse with a slight skew to control and read quantum valley states in ultra-thin 2D semiconductors.
The researchers say that current techniques to control the quantum valley state required complex laser setups using circularly polarized light and multiple laser pulses. On top of that, the control was often incomplete or hard to measure. This means that reliable and reversible switching between the two valley states remained a major challenge. The team has now shown that a single linearly polarized laser pulse can both control and read the valley state of electrons.
The main breakthrough is the use of a small, controlled skew in the laser pulse’s polarization. This slight asymmetry in the laser pulse is enough to push electrons into either the K or K′ valley, and by reversing the skew, the electrons can be switched back to the other valley. This makes the process fully reversible.
Interestingly, the same laser pulse used to control and read the valley, also generates a tiny electric current, which can be used as a signal to reveal in which valley state the electronics moved into - which means that this device can be thus controlled and read at the same time, without the need for extra lasers or measuring devices.