Anomalous softening of phonon dispersion in cuprate superconductors

Abstract

A softening of phonon dispersion has been observed experimentally in underdoped cuprate superconductors at the charge-density-wave (CDW) ordering wave vector. Interestingly, the softening occurs below the superconducting (SC) transition temperature Tc, in contrast to the metallic systems, where the softening occurs usually below the CDW onset temperature TCDW. An understanding of the “anomalous” nature of the phonon softening and its connection to the pseudogap phase in underdoped cuprates remain open questions. Employing a perturbative approach, we find that a complex interplay among the ubiquitous CDW order, SC order, and an unusually connected thermal fluctuations of these orders can explain the anomalous phonon softening below Tc. Furthermore, our formalism captures different characteristics of the low-temperature phonon softening, depending on material specificity.

Source-reported materials — not catalogue approval

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