Unconventional superconductivity and quantum criticality in pressurized CeCu2(Si1−xGex)2

Abstract

CeCu2Si2 plays a crucial role in studying heavy fermion superconductivity and related phenomena. Both the superconducting and normal state properties support the existence of two quantum phase transitions in pressurized CeCu2(Si1−xGex)2. Superconductivity in the low-pressure region occurs around an antiferromagnetic quantum critical point, indicating magnetically mediated superconductivity. A novel superconducting state, likely paired via valence fluctuations, develops around a first-order isostructural volume-collapse transition at high pressures while crossing from the heavy fermion state to the intermediate valence state. In this paper, we briefly review the recent status of CeCu2Si2, in particular its unique properties under pressure.