Fermi-surface collapse and dynamical scaling near a quantum critical point

Abstract

Quantum criticality arises when a macroscopic phase of matter undergoes a continuous transformation at zero temperature. While the collective fluctuations at quantum-critical points are being increasingly recognized as playing an important role in a wide range of quantum materials, the nature of the underlying quantum-critical excitations remains poorly understood. Here we report in-depth measurements of the Hall effect in the heavy-fermion metal YbRh2Si2, a prototypical system for quantum criticality. We isolate a rapid crossover of the isothermal Hall coefficient clearly connected to the quantum-critical point from a smooth background contribution; the latter exists away from the quantum-critical point and is detectable through our studies only over a wide range of magnetic field. Importantly, the width of the critical crossover is proportional to temperature, which violates the predictions of conventional theory and is instead consistent with an energy over temperature, E/T, scaling of the quantum-critical single-electron fluctuation spectrum. Our results provide evidence that the quantum-dynamical scaling and a critical Kondo breakdown simultaneously operate in the same material. Correspondingly, we infer that macroscopic scale-invariant fluctuations emerge from the microscopic many-body excitations associated with a collapsing Fermi-surface. This insight is expected to be relevant to the unconventional finite-temperature behavior in a broad range of strongly correlated quantum systems.

5 pages, plus supporting material

References in corpus (9)

• Fermi-liquid instabilities at magnetic quantum phase transitions
• Quantum Criticality in Heavy Fermion Metals
• Quantum oscillations and the Fermi surface in an underdoped high-Tc superconductor
• Weak magnetism and non-Fermi liquids near heavy-fermion critical points
• Critical fermi surfaces and non-fermi liquid metals
• Multiple energy scales at a quantum critical point
• Magnetic-Field Dependence of the YbRh2Si2 Fermi Surface
• Quantum critical properties of the Bose-Fermi Kondo Model in a large-N limit
• Hall Coefficient in an Interacting Electron Gas

Cited by in corpus (4)

• Heavy Fermions and Quantum Phase Transitions
• Zeeman-driven Lifshitz transition: A scenario for the Fermi-surface reconstruction in YbRh2Si2
• The thermopower as a fingerprint of the Kondo breakdown quantum critical point
• Thermodynamic signatures of a fractionalized Fermi liquid