Electric fields make a ‘tuning knob’ for solid-state systems

Researchers at ETH Zurich in Switzerland have developed a new way of controlling the strength of interactions between particles in two-dimensional semiconductors. Their technique, which relies on generating so-called “Feshbach molecules” and adjusting their interactions using an applied electric field, might well become a versatile “tuning knob” to study a broad range of 2D solid-state platforms in the laboratory.

Feshbach resonances allow researchers to tune the interaction strength between quantum entities by bringing them into resonance with a bound state. In the ETH team’s work, these states correspond to an exciton (an electron-hole pair) in one layer of a two-dimensional material bound to a hole in the adjacent layer. When the exciton (which is created by exciting the material with light) and hole overlap in space, the hole in one layer can then tunnel to the other layer and form an interlayer exciton-hole “molecule”, the researchers explain. It is this exciton-hole interaction strength that they tune by applying a varying electric field to the system.

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