Giant phonon anomaly associated with superconducting fluctuations in the pseudogap phase of cuprates.
Nat Commun 2016;
7:10378. [PMID:
26785835 PMCID:
PMC4735821 DOI:
10.1038/ncomms10378]
[Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 12/04/2015] [Indexed: 11/13/2022] Open
Abstract
The pseudogap in underdoped cuprates leads to significant changes in the electronic structure, and was later found to be accompanied by anomalous fluctuations of superconductivity and certain lattice phonons. Here we propose that the Fermi surface breakup due to the pseudogap, leads to a breakup of the pairing order into two weakly coupled sub-band amplitudes, and a concomitant low energy Leggett mode due to phase fluctuations between them. This increases the temperature range of superconducting fluctuations containing an overdamped Leggett mode. In this range inter-sub-band phonons show strong damping due to resonant scattering into an intermediate state with a pair of overdamped Leggett modes. In the ordered state, the Leggett mode develops a finite energy, changing the anomalous phonon damping into an anomaly in the dispersion. This proposal explains the intrinsic connection between the anomalous pseudogap phase, enhanced superconducting fluctuations and giant anomalies in the phonon spectra.
The emergence of a giant phonon anomaly in the pseudogap phase of underdoped cuprate superconductors has been assumed to be a consequence of instability towards a charge density wave state. Here, the authors present a theory suggesting the anomaly arises due to large superconducting fluctuations.
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