Van Hove singularities play a major role in the physics of certain systems with strong electronic correlations. These are particular points in the electronic band structure where the density of state can become singular. When the Fermi level reaches a van Hove singularity, the electronic correlations are exacerbated, and new phenomena can appear.
In d-wave superconductors, the presence of a van Hove singularity close to the Fermi level can produce remarkable vortex phases. A theoretical prediction has been made of the existence of an original vortex lattice transition corresponding to a 45° rotation of the square symmetry lattice (Nakai et al., Phys. Rev. Lett. 89 237004 (2002)). However, after 20 years of research, this transition had never been observed.
By combining ultrasonic measurements with the intense magnetic fields of the LNCMI, the researchers have discovered an unexpected vortex lattice transition in the superconducting cuprate LaSrCuO (LSCO). With the support of a vortex lattice theory developed by taking into account the particular band structure of LSCO, this work shows that the vortex lattice transition observed here corresponds to the rotation of the square lattice predicted just over 20 years ago.
Publication – Evidence for a Square-Square Vortex Lattice Transition in a High-Tc Cuprate Superconductor
D. J. Campbell, M. Frachet, S. Benhabib, I. Gilmutdinov, C. Proust, T. Kurosawa, N. Momono, M. Oda, M. Horio, K. Kramer, J. Chang, M. Ichioka, and D. LeBoeuf
Phys.
