Interplay of charge density waves, disorder, and superconductivity in 2H-TaSe₂ elucidated by NMR

Abstract

Single crystals of pristine and 6% Pd-intercalated 2H-TaSe2 have been studied by means of 77Se nuclear magnetic resonance (NMR). The temperature dependence of the 77Se spectrum, with an unexpected line narrowing upon Pd intercalation, unravels the presence of correlated local lattice distortions far above the transition temperature of the charge density wave (CDW) order, thereby supporting a strong-coupling CDW mechanism in 2H-TaSe2. While, the Knight shift data suggest that the incommensurate CDW transition involves a partial Fermi surface gap opening. As for spin dynamics, the 77Se spin-lattice relaxation rate T1 -1 as a function of temperature shows that a pseudogap behavior dominates the low-energy spin excitations even within the CDW phase, and gets stronger along with superconductivity in the Pd-6% sample. We discuss that CDW fluctuations may be responsible for the pseudogap as well as superconductivity, although the two phenomena are unlikely to be directly linked each other.

Percolating Superconductivity in Air‐Stable Organic‐Ion Intercalated MoS2

“…While a featureless diamagnetic response is recorded for (CTA) x MoS 2 in the temperature range between 300 and 10 K under an applied field H = 5 KOe, an enhancement in the diamagnetic response is observed for (TEA) y MoS 2 (Figure 2e) in a temperature range corresponding to the increase in the resistance in the transport measurements (Figure 2c). Similar behavior is observed in compounds displaying CDW order, [49,50,52,53] reinforcing our interpretation of the emergence of CDW in (TEA) y MoS 2 .…”

“…This observation is compatible with the presence of a CDW lattice distortion. [ 37,48–50 ] Moreover, (TEA) y MoS 2 displays a superconducting transition below 3.9 K, reaching a well‐defined zero‐resistance final state (Figure 2d). This superconducting transition span 400 mK, a value greater than the one found for perfect, homogenous superconductors.…”

Detection of Nontrivial Topology Driven by Charge Density Wave in a Semi‐Dirac Metal

“…NMR experiments reveal the emergence of only two distinct La species which seems unusual [39] despite the long wavelength associated with the CDW at 211 K. More importantly, the recent observation of coexisting CDW and superconductivity <300 mK, [40] further suggests the presence of a strong electronphonon coupling as has been used to discuss the properties of the cuprates, [41] NbSe 2 , [42] and 2H-TaSe 2 . [43] Electronically, another intriguing aspect is the observation of quasi-linear magnetoresistance (MR) with no saturation with distinct features above and below the CDW transitions. [44] The origin of unsaturated quasi-linear MR at low temperature is still elusive.…”

“…NMR experiments reveal the emergence of only two distinct La species which seems unusual [ 39 ] despite the long wavelength associated with the CDW at 211 K. More importantly, the recent observation of coexisting CDW and superconductivity <300 mK, [ 40 ] further suggests the presence of a strong electron–phonon coupling as has been used to discuss the properties of the cuprates, [ 41 ] NbSe 2 , [ 42 ] and 2H‐TaSe 2 . [ 43 ]…”

Magnetic properties of Fe intercalation FexTaSe2

“…monolayer 1H-TaSe 2 by biaxial strain and charge doping [10], Interplay of CDWs, disorder, and superconductivity in 2H-TaSe 2 elucidated by NMR [11]. To date, relatively few studies have been reported on the preparation of magnetic materials from TaSe 2 by intercalation of ferromagnetic elements.…”