Pressure-tuned quantum criticality in the locally non-centrosymmetric superconductor CeRh${}_2$As${}_2$

Abstract

The unconventional superconductor CeRh${}_2$As${}_2$ (critical temperature $T_{\mathrm{c}}\approx 0.4\mathrm{K}$) 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 $T_0\approx 0.5\mathrm{K}$. Electronic low-temperature properties of CeRh${}_2$As${}_2$ 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 two-phase superconductivity. In this work, using measurements of resistivity and specific heat under hydrostatic pressure, we show that the $T_0$ order vanishes completely at a modest pressure of $P_0=0.5\mathrm{GPa}$, revealing a QCP. In line with the quantum criticality picture, the linear temperature dependence of the resistivity at $P_0$ evolves into a Fermi-liquid quadratic dependence as quantum critical fluctuations are suppressed by increasing pressure. Furthermore, the domelike behavior of $T_{\mathrm{c}}$ around $P_0$ implies that the fluctuations of the $T_0$ order are involved in the SC pairing mechanism.

Includes supplemental material

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Cited by in corpus (9)

• Coexistence of local magnetism and superconductivity in the heavy-fermion CeRh${}_2$As${}_2$ revealed by $\mu$SR studies
• Exposing the odd-parity superconductivity in CeRh${}_2$As${}_2$ with hydrostatic pressure
• Origin of the non-Fermi-liquid behavior in CeRh2As2
• Unified picture of superconductivity and magnetism in CeRh${}_2$As${}_2$
• Superconducting meron phase in locally noncentrosymmetric superconductors
• Quasiclassical theory of vortex states in locally non-centrosymmetric superconductors: application to CeRh${}_2$As${}_2$
• Multipolar fluctuations from localized 4f electrons in CeRh2As2
• La substitution studies on the heavy-fermion superconductor CeRh${}_2$As${}_2$
• Quantum geometric magnetic monopole and two-phase superconductivity in CeRh${}_2$As${}_2$