IIT Bombay Researchers Demonstrate Ultrafast Valley Switching in 2D Semiconductors Using Single Linearly Polarized Pulse

Researchers at the Indian Institute of Technology Bombay have developed a method to control and read quantum valley states in atom-thin two-dimensional (2D) semiconductors using a single linearly polarized laser pulse.

The study, published in Advanced Optical Materials on December 7, 2025 (DOI: 10.1002/adom.202501593), involves authors Gopika N. Gopalan, Amar Bharti, Prachi Venkat, and Gopal Dixit.

The 2D semiconductors, which are one atom thick, feature electrons that occupy two distinct quantum states known as K and K′ valleys. These valleys serve as potential carriers for binary information in valleytronics, similar to 0 and 1 in conventional computing.

Previous approaches to valley control typically required complex setups, including circularly polarized lasers, multiple pulses, carrier-envelope-phase stabilization, and resonant conditions, often with limited ability to achieve full, reversible switching or direct readout.

The new technique introduces a controlled temporal skew — a slight asymmetry — in the polarization waveform of a linearly polarized pulse by delaying its polarization components. This skew selectively drives electrons to either the K or K′ valley, depending on the direction of the skew. Inverting the skew reverses the valley polarization, enabling fully reversible switching.

The same laser puls...