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Pressure-induced enhancement of superfluid density in transition metal dichalcogenides with and without charge density wave

Published inPhysical review research, vol. 7, no. 1, 013324
First online date2025-03-28
Abstract

Gaining a deeper understanding of the interplay between charge density wave (CDW) order and supercon- ductivity in transition metal dichalcogenides (TMDs), particularly within the (4H/2H)-NbX2 (X = Se and S) family, remains an open and intriguing challenge. A systematic microscopic study across various compounds in this family is therefore required to unravel this complex interplay. Here, we report on muon spin rotation (μSR) and magnetotransport experiments investigating the effects of hydrostatic pressure on the superconducting transition temperature (Tc), the temperature-dependent magnetic penetration depth (λeff), and the charge density wave order (CDW) in two layered chalcogenide superconductors: 4H-NbSe2 , which exhibits CDW order, and 2H-NbS2 , which lacks such order. Our observations reveal a substantial 75% enhancement of the superfluid density (ns/m) in 4H-NbSe2 upon the maximum applied pressure of ∼2 GPa, surpassing that of 2H-NbSe2. Despite the absence of CDW order, a sizable 20% growth in superfluid density is also observed for 2H-NbS2 under an applied pressure of 1.8 GPa. Notably, the evaluated superconducting gaps in all these TMDs remain largely unaffected by changes in applied pressure, irrespective of pressure-induced partial suppression of CDW order in (4H/2H)-NbSe2 or its general absence in 2H-NbS2 . These results underscore the complex nature of pressure-induced behaviors in these TMDs, challenging a simplistic view of competition solely between CDW order and superconductivity. Remarkably, the relationship between ns/m and Tc exhibits an unconventional correlation, indicating a noteworthy similarity with the behavior observed in cuprate, kagome, and iron-based superconductors.

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Citation (ISO format)
ISLAM, S. S. et al. Pressure-induced enhancement of superfluid density in transition metal dichalcogenides with and without charge density wave. In: Physical review research, 2025, vol. 7, n° 1, p. 013324. doi: 10.1103/PhysRevResearch.7.013324
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Journal ISSN2643-1564
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