Pressure-Tuned Quantum Criticality in the Locally Noncentrosymmetric Superconductor CeRh2As2

The unconventional superconductor CeRh2As2 (critical temperature Tc≈0.4 K) displays an exceptionally rare magnetic-field-induced transition between two distinct superconducting (SC) phases, proposed to be states of even and odd parity of the SC order parameter, which are enabled by a locally noncentrosymmetric structure. The superconductivity is preceded by a phase transition of unknown origin at T0=0.5 K. Electronic low-temperature properties of CeRh2As2 show pronounced non-Fermi-liquid behavior, indicative of a proximity to a quantum critical point (QCP). The role of quantum fluctuations and normal state orders for the superconductivity in a system with staggered Rashba interaction is currently an open question, pertinent to explaining the occurrence of the two-phase superconductivity. In this work, using measurements of resistivity and specific heat under hydrostatic pressure, we show that the T0 order vanishes completely at a modest pressure of P0≈0.5 GPa, revealing a QCP. In line with the quantum criticality picture, the linear temperature dependence of the resistivity at P0 evolves into a Fermi-liquid quadratic dependence as quantum critical fluctuations are suppressed by increasing pressure. Furthermore, the domelike behavior of Tc around P0 implies that the fluctuations of the T0 order are involved in the SC pairing mechanism.