The Growing Charge-Density-Wave Order in CuTe Lightens and Speeds up Electrons (by Prof. Ming-Wen Chu’s group)
Charge-density waves (CDWs) are common orders in solids and considered to pose electronic correlations that enhance the effective mass (m*) and reduce the Fermi velocity () of carriers. Here, we find out the inversely reduced m* and enhanced in CDW CuTe with gapped practically linearly-dispersing bands, reminiscent of emergent CDW-gapped topological semimetals. Using momentum-dependent electron energy-loss spectroscopy (q-EELS), we simultaneously capture m* and of the CDW-related, linearly-dispersing electrons by plasmon dispersions across the transition (335 K, TCDW), with m* of 0.28 m0 (m0, the electron rest mass) and of ~0.005 c (c, the light speed) at 300 K. Upon the increasing CDW order-parameter strength toward 100 K, the electrons distinctly go lighter and move faster by ~19%. Thorough inspections below TCDW unveil two underlining factors, the frozen fluctuation of the weak-coupling CDW potential and the decreasing light-electron density. The former redeuces electron scattering, with more uniformly distributed potential background, favoring the reduced m* and enhanced . The latter factor analogy to tunable carrier density in suspended-graphene reduces electronic screening, yielding renormalized conical-linear bands with lighter, faster electron, which is similar in our material system. CuTe revisits the CDW correlation notion and urges explorations on m* and across versatile CDW-gapped quantum matters. (This work has been published in Nature Communications,15,9345,(2024).
