Tuning Kitaev and Heisenberg Interactions with Pressure in Ag₃LiRh₂O₆

Magnetic exchange interactions are mediated through orbital overlaps. Thus, tuning the chemical bond angles by physical pressure can tune the relative strength of competing exchange interactions. In a series of X-ray, magnetization, and μSR experiments under pressure, we demonstrated a remarkable case of tuning the Heisenberg and Kitaev interactions in the honeycomb lattice of Ag₃LiRh₂O₆. By combining first-principles calculations and x-ray data obtained under pressure, we demonstrate that pressure increases the ratio of Kitaev to Heisenberg interactions. Consistent with this finding, pressure suppresses the magnetic transition without changing the magnetic moment. We also observe a spontaneous onset of muon spin relaxation oscillations below the Neel temperature at low pressures, unlike at high pressures, where the μSR oscillations do not appear until half the transition temperature. Unlike other candidate Kitaev materials, Ag₃LiRh₂O₆ avoids a structural dimerization as it is tuned toward a quantum critical point by pressure, opening a window to a magnetic quantum critical point.