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Author: Baek, Seung-Ho × Type: Text ×

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    Interplay of charge density waves, disorder, and superconductivity in 2H-TaSe2 elucidated by NMR
    ([London] : IOP, 2022) Baek, Seung-Ho; Sur, Yeahan; Kim, Kee Hoon; Vojta, Matthias; Büchner, Bernd
    Single crystals of pristine and 6% Pd-intercalated 2H‐TaSe2 have been studied by means of 77Se nuclear magnetic resonance. 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.
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    Unusual spin pseudogap behavior in the spin web lattice Cu3TeO6 probed by 125Te nuclear magnetic resonance
    (College Park, MD : APS, 2021) Baek, Seung-Ho; Yeo, Hyeon Woo; Park, Jena; Choi, Kwang-Yong; Büchner, Bernd
    We present a 125Te nuclear magnetic resonance (NMR) study in the three-dimensional spin web lattice Cu3TeO6 which harbors topological magnons. The 125Te NMR spectra and the Knight-shift K as a function of temperature show a drastic change at TS∼40K much lower than the Néel ordering temperature TN∼61K, providing evidence for the first-order structural phase transition within the magnetically ordered state. Most remarkably, the temperature dependence of the spin-lattice relaxation rate T−11 unravels spin-gap-like magnetic excitations, which sharply sets in at T∗∼75K, the temperature well above TN. The spin-gap behavior may be understood by weakly dispersive optical magnon branches of high-energy spin excitations originating from the unique corner-sharing Cu hexagon spin-1/2 network with low coordination number.