Excitonic Bloch-Siegert shift in CsPbI3 perovskite quantum dots

TL;DR

This paper demonstrates room-temperature observation of the excitonic Bloch-Siegert shift in CsPbI3 perovskite quantum dots, revealing strong many-body interactions and providing a model for their interplay with optical effects.

Contribution

It introduces a method to isolate and measure the Bloch-Siegert shift in quantum dots and develops a model accounting for excitonic effects, advancing understanding of light-matter interactions in low-dimensional materials.

Findings

Room-temperature BSS as strong as 4 meV observed.

The BSS/OSE ratio exceeds non-interacting predictions.

A quantitative model incorporating excitonic effects matches experimental data.

Abstract

Coherent interaction between matter and periodic light field induces both optical Stark effect (OSE) and Bloch-Siegert shift (BSS). Observing the BSS has been historically challenging, not only because it is weak but it is often accompanied by a much stronger OSE. Herein, by controlling the light helicity, we can largely restrict the OSE and BSS to different spin-transitions in CsPbI3 perovskite quantum dots, achieving room-temperature BSS as strong as 4 meV with near-infrared pulses. The ratio between the BSS and OSE magnitudes is however systematically higher than the prediction by the non-interacting, quasi-particle picture. With a model that explicitly accounts for excitonic effects, we quantitatively reproduce the experimental observations. This model depicts a unified physical picture of the interplay between the OSE, biexcitonic OSE and BSS in low-dimensional materials displaying strong many-body interactions, forming the basis for the implementation of these effects to information processing, optical modulation and Floquet engineering.