Abstract
Using sound velocity and attenuation measurements in high magnetic fields, we identify a new transition in the vortex lattice state of . The transition, observed in magnetic fields exceeding 35 T and temperatures far below zero field , is detected in the compression modulus of the vortex lattice, at a doping level of . Our theoretical analysis based on Eilenberger’s theory of the vortex lattice shows that the transition corresponds to the long-sought 45° rotation of the square vortex lattice, predicted to occur in -wave superconductors near a van Hove singularity.
- Received 16 November 2021
- Revised 1 March 2022
- Accepted 27 June 2022
DOI:https://doi.org/10.1103/PhysRevLett.129.067001
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