Competing electronic ground states in the heavy-fermion superconductor CeRh₂As₂

CeRh₂As₂ is a rare example of a multiphase superconductor in which magnetic field tunes between two adjacent SC phases. This combined with the local lack of inversion symmetry and an upper critical field exceeding the Pauli paramagnetic limit leads to the possibility of triplet multicomponent superconductivity. In addition to the SC groundstate the f-electron correlations give rise to long-range order, that has both been attributed to local magnetism (AFM) and itinerant (quadrupole) density wave formation. Beyond the application of magnetic field tuning between the SC phases, it provides a perturbation to the f-electron hybridization and can reveal the nature of the manybody correlations. To this end we report a comprehensive magnetization and magnetotransport study on microstructured devices in magnetic fields up to 73 T. For magnetic field applied along c-axis, there is an absence of magnetic phase transitions, yet the transport and Hall effect measurements reveal a field induced delocalization of f-electrons at μ₀H ≈ 22 T. By contrast in-plane application of high magnetic fields, both μ₀H ǁ [100] and [110], reveals a cascade of field induced phases. The field induced in-plane conductivity anisotropy and accompanying lack of magnetic anomalies combined with the “closed-dome” nature of the phases is consistent with a hierarchy of field induced density wave states. By constructing the first T-H phase diagram, we reveal the competition between correlated ground states and the role of magnetic field.