Pressure-modulated competition between dual charge density waves in NbSe₃

Controlling collective electronic states through clean and reversible external stimuli is crucial for realizing functional quantum materials. Here, we report a study on temperature (𝑇) and pressure (𝑃)-tuned charge-density-wave (CDW) orders in the quasi-one-dimensional system of NbS⁢e₃, through single-crystal x-ray diffraction, and electric and magnetotransport measurements. A refined and extended phase diagram is presented, prompting a reevaluation of earlier claims regarding the coexistence of CDW and superconductivity (SC). Here, SC is found to emerge only once all long-range CDWs are suppressed. Notably, the anomalous Hall and magnetoresistance (MR) effects observed at low pressure (LP∼0.8GPa) may arise from distinct carrier types associated with the two competing CDWs, CDW1 and CDW2. These two coexisting CDWs, characterized by distinct modulation vectors, 𝒒_𝟏 and 𝒒_𝟐, show pressure-induced opposing shifts in their 𝑏* axis projections (denoted as 𝑞𝑏*₁ and 𝑞𝑏*₂), while preserving a phase-coupling relationship 2(𝒒_𝟏+𝒒_𝟐) ∼[111]. Upon gradual suppression of the long range order CDW2 order, 𝑞𝑏*₁ of CDW1 stabilizes and enters a decoupled regime within ∼0.8−1.3 GPa, followed by a pronounced change in its periodicity between ∼1.3 and 2.9 GPa. Above 2.9 GPa, all long-range CDW orders vanish, giving way to emergent superconductivity (SC).