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Critical Fluctuations and Conserved Dynamics in a Strange Ferromagnetic Metal

Jin Zhan1,*, Yongjun Zhang2,*, Jiawen Zhang1, Yu Liu1, Zhiyong Nie1, Yuxin Chen1, Lin Jiao1, Yashar Komijani3, Michael Smidman1,† et al.

Frank Steglich1,4, Piers Coleman5,6,‡, and Huiqiu Yuan1,7,8,9,§

  • *These authors contributed equally to this work.
  • †Contact author: msmidman@zju.edu.cn
  • ‡Contact author: coleman@physics.rutgers.edu
  • §Contact author: hqyuan@zju.edu.cn
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Phys. Rev. Lett. 135, 266504 – Published 31 December, 2025

DOI: https://doi.org/10.1103/bp6l-46z7

Abstract

The origin of the strange metallic behavior observed in a wide range of quantum materials is an open challenge to condensed matter physics. Historically, strange metals were uniquely associated with antiferromagnetic quantum critical points (QCPs), but a new generation of materials reveals their association with uniform order parameters, such as ferromagnetism, valley, or nematic order, suggesting a deeper common denominator. At a QCP, order parameter fluctuations are characterized by the dynamical critical exponent z, which quantifies the space-time scaling asymmetry. Here, we report the observation of a divergence in the Grüneisen ratio at the QCP of the strange-metal ferromagnet CeRh6Ge4 with a dynamical critical exponent z=3, signaling that the underlying quantum singularity involves a conserved degree of freedom. Yet the magnetization of this easy-plane ferromagnet is not conserved. We argue that the z=3 strange criticality requires a description beyond the Landau paradigm, proposing a link with the gauge modes of the small-to-large Fermi surface transition and the associated gauge charge of the delocalizing heavy electrons.

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Phys. Rev. Lett. 135, 266504– Published 31 December, 2025
  • Received 2 May 2025
  • Revised 30 September 2025
  • Accepted 1 December 2025
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