Speaker
Description
High-order Van Hove singularities significantly enhance correlation effects due to their strongly divergent density of states, thereby providing natural platforms for interaction driven instabilities. In this work, we focus on a single fourfold-symmetric high-order Van Hove singularity of X_9 type situated close to the Fermi surface. We analyse the possibility of a superconducting state in the presence of nominally weak Hubbard interactions, via the Kohn-Luttinger type mechanism. We find that the leading instability occurs in the triplet p-wave channel with critical temperature scaling as T_c ∝ U^2. We discuss the fluctuations in connection to lower dimensionality, and the condition to stabilise a triplet superconducting state. Our results are relevant to the benchmark quantum material Sr_3Ru_2O_7 which hosts an X9 singularity in the presence of an external magnetic field, and we estimate an upper bound on the critical temperature in this system. More broadly, our work suggests a potential route to superconductivity in materials capable of hosting an X_9 singularity.
Work to appear in Physical Review Research, DOI: https://doi.org/10.1103/jdr9-4f95
The work has been supported by the UK Engineering Physical Sciences Research Council grants EP/T034351/1 and EP/X012557/1.