Dzyaloshinskii-Moriya interactions and deconfined criticality in SrCu$_2$(BO$_3$)$_2$

Abstract

SrCu$_2$(BO$_3$)$_2$ is the leading candidate for deconfined criticality, yet theories of its critical regime omit the Dzyaloshinskii-Moriya (DM) interactions, which gap the kagome Dirac spin liquid. Adding them to the SU(2) gauge theory, we show that time reversal and a spin-orbit-locked glide forbid any gauge-singlet spinon mass to all orders. In-plane DM only twists the spinons, reconstructing the nodes below $0.03$-$0.17$ K, while out-of-plane DM is irrelevant and SO(5) anisotropy arises only at second order. The material thus remains a platform for deconfined criticality, which NMR can test, since a $[100]$ field induces a N\'eel moment and a $[001]$ field does not.