Signatures of quantum criticality in pure Cr at high pressure

School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 08/2010; 107(31):13631-5. DOI: 10.1073/pnas.1005036107
Source: PubMed


The elemental antiferromagnet Cr at high pressure presents a new type of naked quantum critical point that is free of disorder and symmetry-breaking fields. Here we measure magnetotransport in fine detail around the critical pressure, Pc approximately 10 GPa, in a diamond anvil cell and reveal the role of quantum critical fluctuations at the phase transition. As the magnetism disappears and T-->0, the magnetotransport scaling converges to a non-mean-field form that illustrates the reconstruction of the magnetic Fermi surface, and is distinct from the critical scaling measured in chemically disordered CrV under pressure. The breakdown of itinerant antiferromagnetism only comes clearly into view in the clean limit, establishing disorder as a relevant variable at a quantum phase transition.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: YbRh(2)Si(2) is a model system for quantum criticality. In particular, Hall effect measurements helped identify the unconventional nature of its quantum critical point. Here, we present a high-resolution study of the Hall effect and magnetoresistivity on samples of different quality. We find a robust crossover on top of a sample dependent linear background contribution. Our detailed analysis provides a complete characterization of the crossover in terms of its position, width, and height. Importantly, we find in the extrapolation to zero temperature a discontinuity of the Hall coefficient occurring at the quantum critical point for all samples. In particular, the height of the jump in the Hall coefficient remains finite in the limit of zero temperature. Hence, our data solidify the conclusion of a collapsing Fermi surface. Finally, we contrast our results to the smooth Hall effect evolution seen in chromium, the prototype system for a spin-density-wave quantum critical point.
    Full-text · Article · Feb 2011 · Journal of Physics Condensed Matter
  • [Show abstract] [Hide abstract]
    ABSTRACT: The magnetic behavior and possibility of quantum criticality in a (Cr0.98Si0.02)1−yMoy alloy system (0 ≤ y ≤ 0.09) is investigated through electrical resistivity, specific heat, and thermoelectric power measurements in a temperature range 2–350 K. Alloys with 0 ≤ y ≤ 0.011 depict first-order Néel transitions that give way to continuous Néel transitions for 0.011 < y ≤ 0.038. The Néel temperature, TN(y), seems to be suppressed down to 0 K at a critical concentration yc ≈ 0.04. The Sommerfeld coefficient of specific heat γ(y) peaks at y ≈ yc, showing a sharp decreasing trend on decreasing y to below yc. This behavior is reminiscent of that observed for γ of the prototypical Cr1−xVx quantum critical system, and indeed also portrays the physics of a quantum critical point in the present (Cr0.98Si0.02)1−yMoy system.
    No preview · Article · Mar 2011 · Journal of Applied Physics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Electrical resistivity, specific heat, and magnetization measurements on URu2−xFexSi2 reveal a twofold enhancement of the “hidden-order” (HO)/large-moment antiferromagnetic (LMAFM) phase boundary T0(x). The T0(Pch) curve, obtained by converting x to “chemical pressure” Pch, is strikingly similar to the T0(P) curve, where P is applied pressure, for URu2Si2 both exhibit a “kink” at 1.5 GPa and a maximum at ∼7 GPa. This similarity suggests that the HO-LMAFM transition at 1.5 GPa in URu2Si2 occurs at x ≈ 0.2 (Pch≈1.5 GPa) in URu2−xFexSi2. URu2−xFexSi2 provides an opportunity for studying the HO and LMAFM phases with methods that probe the electronic structure [e.g., scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES), and point-contact spectroscopy (PCS)] but cannot be used under pressure.
    Preview · Article · Dec 2011 · Physical Review B
Show more