Competing electronic ground states in the heavy-fermion superconductor CeRh2As2

TL;DR

This study investigates the complex magnetic and electronic phase behavior of CeRh2As2, revealing multiple field-induced phase transitions and suggesting the presence of unconventional superconductivity and density-wave states.

Contribution

It provides comprehensive high-field magnetization and transport data on CeRh2As2, elucidating the nature of its competing ground states and the effects of magnetic field on its electronic correlations.

Findings

Field induces a valence transition at ~24 T along c-axis.

In-plane fields cause multiple phase transitions with anisotropic conductivity.

Phase boundary forms a closed dome indicating density-wave states.

Abstract

CeRh2As2 is rare among superconductors, in that magnetic field tunes it between two distinct superconducting phases. Combined with a lack of local inversion symmetry and an upper critical field exceeding the Pauli paramagnetic limit, this excitingly suggests triplet multicomponent superconductivity. Preceding the superconducting onset, f-electron correlations cause long-range order, attributed both to local antiferromagnetism and itinerant (quadrupole) density-waves. Magnetic field provides a significant perturbation of the f-electron and may reveal the nature of the many-body correlations. Thus, we report comprehensive magnetization and magnetotransport studies on microstructured devices in fields of up to 73 T. Applied along the c-axis, field causes a low-temperature valence transition at {\mu}0H ~ 24 T. By contrast, in-plane fields produce a cascade of phase transitions; the field-induced in-plane conductivity anisotropy and lack of accompanying magnetic features, plus the closed-dome nature of the overall phase boundary is consistent with a hierarchy of field-induced density-wave states.