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

Meike Pfeiffer; Konstantin Semeniuk; Javier F. Landaeta; Robert Borth; Christoph Geibel; Michael Nicklas; Manuel Brando; Seunghyun Khim; Elena Hassinger

doi:10.1103/physrevlett.133.126506

arXiv · 2312.09728

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

Meike Pfeiffer·Konstantin Semeniuk·Javier F. Landaeta·Robert Borth·Christoph Geibel·Michael Nicklas·Manuel Brando·Seunghyun Khim·Elena Hassinger

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Abstract

The unconventional superconductor CeRh$_2$As$_2$ (critical temperature $T_{\mathrm{c}}\approx0.4\,\mathrm{K}$) 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 $T_{0}\approx0.5\,\mathrm{K}$. 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.

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Meike Pfeiffer, Konstantin Semeniuk, Javier F. Landaeta, Robert Borth, Christoph Geibel, Michael Nicklas, Manuel Brando, Seunghyun Khim, Elena Hassinger. 2023-12-15. Pressure-tuned quantum criticality in the locally non-centrosymmetric superconductor CeRh$_2$As$_2$. https://doi.org/10.1103/physrevlett.133.126506

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