Hierarchy of energy scales in an O(3) symmetric antiferromagnetic quantum critical metal: A Monte Carlo study
Abstract
We present numerically exact results from signproblem free quantum Monte Carlo simulations for a spinfermion model near an O(3) symmetric antiferromagnetic (AFM) quantum critical point. We find a hierarchy of energy scales that emerges near the quantum critical point. At highenergy scales, there is a broad regime characterized by Landaudamped order parameter dynamics with dynamical critical exponent z =2 , while the fermionic excitations remain coherent. The quantum critical magnetic fluctuations are well described by HertzMillis theory, except for a T^{2} divergence of the static AFM susceptibility. This regime persists down to a lowerenergy scale, where the fermions become overdamped and, concomitantly, a transition into a d wave superconducting state occurs. These findings resemble earlier results for a spinfermion model with easyplane AFM fluctuations of an O(2) spin density wave (SDW) order parameter, despite noticeable differences in the perturbative structure of the two theories. In the O(3) case, perturbative corrections to the spinfermion vertex are expected to dominate at an additional energy scale, below which the z =2 behavior breaks down, leading to a novel z =1 fixed point with emergent local nesting at the hot spots [Schlief et al., Phys. Rev. X 7, 021010 (2017), 10.1103/PhysRevX.7.021010]. Motivated by this prediction, we also consider a variant of the model where the hot spots are nearly locally nested. Within the available temperature range in our study (T ≥E_{F}/200 ), we find substantial deviations from the z =2 HertzMillis behavior, but no evidence for the predicted z =1 criticality.
 Publication:

Physical Review Research
 Pub Date:
 April 2020
 DOI:
 10.1103/PhysRevResearch.2.023008
 arXiv:
 arXiv:2001.00586
 Bibcode:
 2020PhRvR...2b3008B
 Keywords:

 Condensed Matter  Strongly Correlated Electrons;
 Condensed Matter  Superconductivity
 EPrint:
 13 pages, 18 figures, corrected affiliation information and acknowledgments