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Spin fluctuations in normal state CeCu2Si2 on approaching the quantum critical point
Julia Arndt1, Oliver Stockert, Karin Schmalzl
1Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany. Julia.Arndt@ilkdresden.de
Researchers observed critical slowing-down in heavy-fermion superconductor CeCu2Si2 approaching a quantum critical point (QCP). This finding suggests overdamped spin fluctuations mediate Cooper pair coupling, offering new insights into superconductivity mechanisms.
Area of Science:
- Condensed Matter Physics
- Quantum Materials Science
Background:
- Heavy-fermion superconductors like CeCu2Si2 exhibit complex electronic properties near magnetic instabilities.
- Understanding the interplay between superconductivity and magnetic quantum criticality is crucial for novel material design.
Purpose of the Study:
- To investigate the magnetic excitation spectrum in CeCu2Si2 approaching a quantum critical point (QCP).
- To elucidate the role of magnetic fluctuations in mediating superconductivity in heavy-fermion systems.
Main Methods:
- Inelastic neutron scattering to probe the magnetic excitation spectrum.
- Analysis of specific heat data.
- Investigation of the momentum dependence of magnetic excitations.
Main Results:
- Observed a transfer of spectral weight to higher energies in the superconducting state, indicating a spin excitation gap.
- Detected a critical slowing-down of quasielastic magnetic response in the normal state, consistent with spin-density-wave QCP scaling.
- Provided the first direct evidence of near-critical slowing of normal-state magnetic response at a QCP upon suppressing superconductivity.
Conclusions:
- The results strongly imply that overdamped spin fluctuations mediate the coupling of Cooper pairs in CeCu2Si2.
- This study highlights the significant role of magnetic fluctuations in the unconventional superconductivity of heavy-fermion compounds.
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