Development of the critical exponent at the antiferromagnetic phase transition of YbRh2Si2 under chemical pressure

TL;DR

This study investigates how chemical pressure via Co doping affects the critical behavior of the antiferromagnetic transition in YbRh2Si2, revealing a change in critical exponents and linking it to quantum criticality.

Contribution

It demonstrates the evolution of the critical exponent at the antiferromagnetic transition under chemical pressure, providing insight into universality class changes and quantum critical effects.

Findings

Critical exponent a changes from positive to negative with Co doping.

Chemical pressure influences the universality class of the phase transition.

Violation of critical universality linked to proximity to quantum critical point.

Abstract

We present specific-heat measurements in the vicinity of the antiferromagnetic phase transition on single crystals of the alloy Yb(Rh_{1-x}Co_x)2Si2 for x<= 0.38. This study was motivated by the violation of critical universality in the undoped YbRh2Si2 (Krellner et al., Phys. Rev. Lett. 102, 196402) where we have found a large critical exponent a=0.38. For Co-doped samples we observe a drastic change of the critical fluctuations resulting in a negative a, explainable within the universality classes of phase transitions. The development of a under chemical pressure gives strong indication that the violation of critical universality in YbRh2Si2 is due to the nearby quantum critical point.