Charge density wave (CDW) and their interplay with correlated and topological quantum states are at the forefront of condensed matter research. The $4H_b\text{−}{\mathrm{TaS}}_2$ is a CDW ordered quantum heterostructure that is formed by alternative stacking of Mott insulating 1T-${\mathrm{TaS}}_2$ and Ising superconducting 1H-${\mathrm{TaS}}_2$. While the $\sqrt{13}\times \sqrt{13}$ and $3\times 3$ CDWs have been respectively observed in the bulk 1T-${\mathrm{TaS}}_2$ and 2H-${\mathrm{TaS}}_2$, the CDWs and their pivotal role for unconventional superconductivity in the $4H_b\text{−}{\mathrm{TaS}}_2$ remain unsolved. In this Letter, we reveal the two-dimensional (2D) $\sqrt{13}\times \sqrt{13}$ chiral CDW in the 1T layers and intraunit cell coupled 2D $2\times 2$ CDW in the 1H and 1H' layers of $4H_b\text{−}{\mathrm{TaS}}_2$. Our results establish $4H_b\text{−}{\mathrm{TaS}}_2$ a 2.5D quantum heterostructure, where 2D quantum states emerge from 3D crystalline structure.

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• Charge density waves
• Quantum crystals
• Transition metal dichalcogenides
• Unconventional superconductors
• X-ray techniques