Abstract
Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations. In a multidomain system this signifies nonlocal coherence and emergence of collective phenomena, particularly in layered 2D quantum materials possessing novel electronic structures and high carrier mobilities. Here we report nonlocal ac electron coherence induced in dispersed MoS2 flake domains, using coherent spatial self-phase modulation (SSPM). The gap-dependent nonlinear dielectric susceptibility χ(3) measured is surprisingly large, where direct interband transition and two-photon SSPM are responsible for excitations above and below the bandgap, respectively. A wind-chime model is proposed to account for the emergence of the ac electron coherence. Furthermore, all-optical switching is achieved based on SSPM, especially with two-color intraband coherence, demonstrating that electron coherence generation is a ubiquitous property of layered quantum materials.
Highlights
Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations
By using coherent spatial self-phase modulation (SSPM) we observed the emergence of electron coherence in a gapped quantum material, MoS2
By observing gap-dependent SSPM we discovered that it is a ubiquitous property of two-dimensional layered quantum materials
Summary
Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations. All-optical switching is achieved based on SSPM, especially with two-color intraband coherence, demonstrating that electron coherence generation is a ubiquitous property of layered quantum materials. The SSPM is a coherent third-order nonlinear optical process systematically investigated decades ago [22], where the nonlinear optical susceptibility χ(3) is uniquely determined by the laser-intensity-dependent refractive index n = n0 + n2I, where n0 and n2 are linear and nonlinear refractive indexes, respectively. If this effect is strong enough in a material, the phenomenon of selffocusing can be directly observed. This optical switch has multiple advantages, including weak-control-strong performance, cascade-possible, and high-contrast two-color switching
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