The properties of van der Waals heterostructures are drastically altered by a tunable moiré superlattice arising from periodically varying atomic alignment between the layers. Exciton diffusion represents an important channel of energy transport in transition metal dichalcogenides (TMDs). While early studies performed on TMD heterobilayers suggested that carriers and excitons exhibit long diffusion, a rich variety of scenarios can exist. In a moiré crystal with a large supercell and deep potential, interlayer excitons may be completely localized. As the moiré period reduces at a larger twist angle, excitons can tunnel between supercells and diffuse over a longer lifetime. The diffusion should be the longest in commensurate heterostructures where the moiré superlattice is completely absent. Here, we experimentally demonstrate the rich phenomena of interlayer exciton diffusion in WSe₂/MoSe₂ heterostructures by comparing several samples prepared with chemical vapor deposition and mechanical stacking with accurately controlled twist angles.

范德华异质结构的性质因层间周期性变化的原子排列而产生的可调谐莫尔超晶格而发生巨大改变。激子扩散是过渡金属二硫属化物（TMD）中能量传输的重要通道。虽然对 TMD 异质双层进行的早期研究表明载流子和激子表现出长扩散，但可能存在多种情况。在具有大超晶胞和深电势的莫尔晶体中，层间激子可能完全局域化。随着莫尔周期在更大的扭转角下减小，激子可以在超级电池之间隧道并在更长的寿命内扩散。在完全不存在莫尔超晶格的相称异质结构中，扩散应该是最长的。在这里，我们通过比较化学气相沉积和精确控制扭转角的机械堆叠制备的几个样品，实验证明了WSe ₂ /MoSe ₂异质结构中丰富的层间激子扩散现象。