T-linear specific heat in pressurized and magnetized Shastry-Sutherland Mott insulator SrCu2(BO3)2

TL;DR

This study reveals a universal T-linear specific heat in pressurized and magnetized SrCu2(BO3)2, suggesting gapless excitations possibly due to magnetized Dirac spinons, challenging existing theories of this frustrated quantum magnet.

Contribution

It uncovers a new universal T-linear specific heat phase in SrCu2(BO3)2 under pressure and magnetic field, linked to magnetized Dirac spinons, expanding understanding of its phase diagram.

Findings

T-linear specific heat observed in pressurized, magnetized SrCu2(BO3)2

Gapless response attributed to magnetized Dirac spinons

Phase diagram enriched by pressure and magnetic field axes

Abstract

The pressurized Shastry-Sutherland Mott insulator SrCu2(BO3)2 has been found to host a plaquette-singlet phase and an antiferromagnetic phase that break different symmetries spontaneously.The recent experiment showed that their transition is of a first order nature, which seems against the pursuit of exotic and deconfined degrees of freedom in this famous frustrated quantum magnet. We found a new direction in this study. By applying a magnetic field to the material, we discover that SrCu2(BO3)2 exhibits a universal and metallic T-linear specific heat behavior in a large magnetitic field range close to the pressure of zero-field first order transition between plaquette-singlet and antiferromagnetic phases. Such an unexpected gapless response from an electronically gapped Mott insulator could be attributed to magnetized Dirac spinons liberated by the combined effect of magnetic field and pressure, consistently seen from our quantum many-body thermal tensor network computation of the Shastry-Sutherland model under magnetic field. Such a robust and universal T-linear specific heat phase points out the richness of the phase diagram of the material expanded by the axes of pressure and magnetic field and is calling for new theoretical frameworks to its full explanation.