• Open Access

Non-Fermi Liquid at (2+1)D Ferromagnetic Quantum Critical Point

Xiao Yan Xu, Kai Sun, Yoni Schattner, Erez Berg, and Zi Yang Meng
Phys. Rev. X 7, 031058 – Published 27 September 2017

Abstract

We construct a two-dimensional lattice model of fermions coupled to Ising ferromagnetic critical fluctuations. Using extensive sign-problem-free quantum Monte Carlo simulations, we show that the model realizes a continuous itinerant quantum phase transition. In comparison with other similar itinerant quantum critical points (QCPs), our QCP shows a much weaker superconductivity tendency with no superconducting state down to the lowest temperature investigated, hence making the system a good platform for the exploration of quantum critical fluctuations. Remarkably, clear signatures of non-Fermi liquid behavior in the fermion propagators are observed at the QCP. The critical fluctuations at the QCP partially resemble Hertz-Millis-Moriya behavior. However, careful scaling analysis reveals that the QCP belongs to a different universality class, deviating from both (2+1)D Ising and Hertz-Millis-Moriya predictions.

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  • Received 30 December 2016

DOI:https://doi.org/10.1103/PhysRevX.7.031058

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsStatistical Physics & Thermodynamics

Authors & Affiliations

Xiao Yan Xu1, Kai Sun2, Yoni Schattner3, Erez Berg3, and Zi Yang Meng1

  • 1Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 2Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
  • 3Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel 76100

Popular Summary

A conducting or itinerant electron in a metal interacts with its fellow electrons and the atomic nuclei in the material in a complex way. The net effect of the interactions is to make the electron behave as if its basic properties were modified, in other words, as a so-called “quasiparticle.” For most metals, the lifetime of a quasiparticle becomes infinite as the temperature approaches absolute zero, resulting in a finite quasiparticle “residue.” This behavior matches predictions from Fermi-liquid theory, a theoretical model that successfully describes how particles in most metals interact with each other at low temperature. But for certain metals, such as those on the brink of a sudden change in magnetic properties, the Fermi-liquid theory fails. The quasiparticle residue in these “strange metals” vanishes as the temperature drops to zero. We developed computer simulations to examine this behavior in detail for one example of a strange metal.

Specifically, we studied strange metal behaviors near the ferromagnetic phase transition, where the itinerant electrons are strongly correlated with the long-range magnetic mode. Because the electrons are itinerant, the magnetic mode is long-ranged, and the correlation is strong; any analytical method that is based on approximations is not well suited to resolve this problem. We designed a state-of-the-art, sign-problem-free, quantum Monte Carlo simulation to solve this problem exactly. We observed clear signatures of non-Fermi-liquid behaviors near the ferromagnetic phase transition. More remarkably, quantum critical analysis indicates it is a new critical point with an anomalous scaling exponent.

These results not only sharpen the theoretical understanding about itinerant quantum criticality—where phase transitions occur at absolute zero—but also offer important theoretical guidance to experimental investigations on various strongly correlated metals.

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Vol. 7, Iss. 3 — July - September 2017

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