Berlin 2024 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 4: f-Electron Systems
TT 4.1: Hauptvortrag
Montag, 18. März 2024, 09:30–10:00, H 3005
Hyperfine interactions and nuclear-electronic quantum criticality in PrOs4Sb12 — •Alix McCollam — School of Physics, University College Cork, Ireland
Many strongly correlated electron systems develop ordered phases at low temperatures that can be well understood in terms of an electronic order parameter. At ultra-low temperatures, however, the hyperfine interaction becomes increasingly important, and we must consider how this affects ordered phases and phase transitions near T = 0.
PrOs4Sb12 is a superconductor below TC = 1.85 K and HC2 = 2.2 T, and develops antiferroquadrupolar (AFQ) order in magnetic fields between ∼ 4 T and 14 T. The hyperfine constant of Pr is relatively large at 52 mK, and influences the Pr crystal electric field levels that are closely involved in both the superconducting and AFQ phases.
To explore this influence, we performed magnetic susceptibility measurements as a function of temperature and magnetic field to temperatures as low as 1 mK. We find that the phase boundaries in PrOs4Sb12 show anomalous behaviour down to ∼ 5 mK: AFQ order is enhanced at low temperature, whereas superconductivity is suppressed.
We explain our results in terms of a ground state composed of hybrid nuclear-electronic states with novel low energy excitations. The low temperature quadrupole excitations develop from these nuclear-electronic states, and are considerably modified compared to their higher temperature counterparts. Our results indicate a novel type of nuclear-electronic quantum critical point at the AFQ transition.
Keywords: ultralow temperature; quantum criticality; electronuclear order; superconductivity; PrOs4Sb12