Engineering Surface Critical Behavior of (2+1)-Dimensional O(3) Quantum Critical Points

TL;DR

This paper investigates the surface critical behavior of (2+1)-dimensional O(3) quantum critical points in dimerized Heisenberg models, revealing three universality classes and challenging existing theories with novel surface phenomena.

Contribution

It demonstrates the realization of three types of surface critical behavior in quantum critical points by engineering surface configurations, including a novel extraordinary transition that defies current scaling theory.

Findings

Identification of three surface critical behavior types in quantum critical points.

Discovery of a surface-induced extraordinary transition with anomalous critical exponents.

Challenge to existing scaling theory through observed violations in surface critical exponents.

Abstract

Surface critical behavior (SCB) refers to the singularities of physical quantities on the surface at the bulk phase transition. It is closely related to and even richer than the bulk critical behavior. In this work, we show that three types of SCB universality are realized in the dimerized Heisenberg models at the (2+1)-dimensional O(3) quantum critical points by engineering the surface configurations. The ordinary transition happens if the surface is gapped in the bulk disordered phase, while the gapless surface state generally leads to the multicritical special transition, even though the latter is precluded in classical phase transitions because the surface is in the lower critical dimension. An extraordinary transition is induced by the ferrimagnetic order on the surface of the staggered Heisenberg model, in which the surface critical exponents violate the results of the scaling theory and thus seriously challenge our current understanding of extraordinary transitions.