Unconventional and conventional quantum criticalities in CeRh0.58Ir0.42In5

• Published in: npj quantum materials Vol. 3; no. 1
• Main Authors: Luo, Yongkang, Lu, Xin, Dioguardi, Adam P., Rosa, Priscila S. F., Bauer, Eric D., Si, Qimiao, Thompson, Joe D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.02.2018; Nature Publishing Group
• Subjects: 639/301/119/1003; 639/301/119/2795; 639/301/119/997; Broken symmetry; Charge transport; Condensed Matter Physics; Critical point; Fermi liquids; Fermi surfaces; Fermions; Material Science; MATERIALS SCIENCE; Phase diagrams; Phase transitions; Physics; Physics and Astronomy; Pressure dependence; Quantum Physics; Reconstruction; Specific heat; Spin density waves; Structural Materials; Surfaces and Interfaces; Temperature dependence; Thermoelectricity; Thin Films; Transport properties; Unconventional superconductivity
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-018-0080-9

An appropriate description of the state of matter that appears as a second order phase transition is tuned toward zero temperature, viz. quantum-critical point (QCP), poses fundamental and still not fully answered questions. Experiments are needed both to test basic conclusions and to guide further refinement of theoretical models. Here, charge and entropy transport properties as well as AC specific heat of the heavy-fermion compound CeRh 0.58 Ir 0.42 In 5 , measured as a function of pressure, reveal two qualitatively different QCPs in a single material driven by a single non-symmetry-breaking tuning parameter. A discontinuous sign-change jump in thermopower suggests an unconventional QCP at p c 1 accompanied by an abrupt Fermi-surface reconstruction that is followed by a conventional spin-density-wave critical point at p c 2 across which the Fermi surface evolves smoothly to a heavy Fermi-liquid state. These experiments are consistent with some theoretical predictions, including the sequence of critical points and the temperature dependence of the thermopower in their vicinity. Strongly correlated systems: One material, two quantum critical points Two qualitatively different quantum critical points—QCPs, points in the phase diagram where continuous transitions happen at zero temperature—are encountered in a heavy-fermion material under pressure. Better understanding heavy-fermion materials, so called because of their electrons’ large effective mass, is important to shed light on non-Fermi liquid and unconventional superconductivity. A team led by Yongkang Luo and Joe Thompson at Los Alamos National Laboratory, USA, measured the pressure-dependent resistivity, thermopower and AC specific heat of the heavy-fermion compound CeRh 0.58 Ir 0.42 In 5 , unveiling an unconventional QCP accompanied by a sudden Fermi surface reconstruction, followed by a conventional spin-density wave QCP and finally by a heavy Fermi-liquid state. The results agree with theoretical predictions and suggest that thermopower can be used to investigate Fermi surfaces when direct measurements are unavailable. Moreover, the gained insights should be generally applicable to QCPs in heavy-fermion materials.