Coherent interaction between matter and light field induces both optical Stark effect and Bloch–Siegert shift. Observing the latter has been historically challenging, because it is weak and is often accompanied by a much stronger Stark shift. Herein, by controlling the light helicity, we can largely restrict these two effects to different spin-transitions in CsPbI₃ perovskite quantum dots, achieving room-temperature Bloch–Siegert shift as strong as 4 meV with near-infrared pulses. The ratio between the Bloch–Siegert and optical Stark shifts is however systematically higher than the prediction by the non-interacting, quasi-particle model. With a model that explicitly accounts for excitonic effects, we quantitatively reproduce the experimental observations. This model depicts a unified physical picture of the optical Stark effect, biexcitonic optical Stark effect and Bloch–Siegert shift 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.

物质和光场之间的相干相互作用引起了光学斯塔克效应和布洛赫-西格特位移。观察后者在历史上一直具有挑战性，因为它很弱，并且通常伴随着更强烈的斯塔克转变。在此，通过控制光螺旋度，我们可以在很大程度上将这两种效应限制在 CsPbI _{3中的不同自旋跃迁上}钙钛矿量子点，在近红外脉冲下实现了高达 4 meV 的室温 Bloch-Siegert 位移。然而，布洛赫-西格特位移和光学斯塔克位移之间的比率系统地高于非相互作用准粒子模型的预测。通过明确解释激子效应的模型，我们定量地再现了实验观察结果。该模型描绘了显示强多体相互作用的低维材料中的光学斯塔克效应、双激子光学斯塔克效应和布洛赫-西格特位移的统一物理图像，为将这些效应应用于信息处理、光调制和Floquet工程。