Probing Spin-Excitaions above the Ground State of 1T-TaS₂

Spin-spin interactions can lead to exotic ground states with emergent excitations in frustrated quantum magnets. Such a system is the transition metal dichalcogenide 1T-TaS₂ .While the material is electrically insulating and exhibits no magnetic ordering down to milikelvin temperatures, the specific heat has a linear fermionic-type contribution that suggests a large band-width. We analyse the low temperature specific heat data and torque magnetometry measurements to isolate the contribution of the spin excitations to the magnetization from the large background response. The magnetic torque is strongly anisotropic and has a singular response at low magnetic fields which we attribute to a continuous disassociation of singlet pairs. This picture is also supported by the perfect collapse of the specific heat data at various temperatures and magnetic fields onto a universal curve predicted for singlets with a random distribution of antiferromagnetic coupling strengths. We interpret our data in the framework of a quantum spin liquid ground state having a large bandwidth with minority spins forming an array of singlet pairs with a continuum of coupling constants. Finally, despite the presumed large spinon Fermi surface we could not observe quantum oscillations of the magnetization.