Argonne National Laboratory

Research Highlight | Materials Science

Leggett modes and crystallographic phase transitions
In a study published in Physical Review X, researchers report that a mode first identified by Tony Leggett in multi-band superconductors has a counterpart for structural phase transitions.
Free energy surfaces for the two primary structural order parameters of the ferroelectric, Cd₂Nb₂O₇ Arrows indicate oscillations on the free energy surfaces associated with collective ionic motion. The wavy line denotes the coupling between the two surfaces that gives rise to either Goldstone-like (in-phase oscillations) or Leggett-like (out-of-phase oscillations) behavior.

Scientific Achievement

It is demonstrated that the Leggett mode, a collective oscillation of multi-band superconductors, has a counterpart for structural phase transitions.

Significance and Impact

The elucidation of new modes for collective ionic motion should give new insights into complex materials such as relaxor ferroelectrics.

Research Details

  • We have performed a free energy analysis of the pyrochlore, Cd2Nb2O7, and elucidated the potential presence of out-of-phase amplitude (anti-phase Higgs) modes and out-of-phase phase (anti-phason) modes.
  • We have used our insight to propose new experiments that could be done, such as pump-probe measurements and local structural studies (diffuse scattering, etc.).

DOI: 10.1103/PhysRevX.12.011024

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