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Open Access Publications from the University of California

Quantum critical kondo quasiparticles probed by ESR in β-YbAlB 4

  • Author(s): Holanda, LM
  • Vargas, JM
  • Iwamoto, W
  • Rettori, C
  • Nakatsuji, S
  • Kuga, K
  • Fisk, Z
  • Oseroff, SB
  • Pagliuso, PG
  • et al.

Electron spin resonance (ESR) can probe conduction electrons (CE) and local moment (LM) spin systems in different materials. A CE spin resonance (CESR) is observed in metallic systems based on light elements or with enhanced Pauli susceptibility. LM ESR can be seen in compounds with paramagnetic ions and localized d or f electrons. Here we report a remarkable and unprecedented ESR signal in the heavy-fermion superconductor β-YbAlB4 which behaves as a CESR at high temperatures and acquires characteristics of the Yb3 LM ESR at low temperature. This dual behavior strikes as an in situ unique observation of the Kondo quasiparticles in a quantum critical regime. The proximity to a quantum critical point may favor the appearance of this dual character of the ESR signal in β-YbAlB4. © 2011 American Physical Society.

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