Quantum spin liquid (QSL) is a novel state of matter where the ground states are quantum mechanically entangled and have several characteristic features, including fractional excitations. However, the nature of QSLs remains elusive. To tackle this problem, studying the effect of quenched disorder is of vital importance.
Recently, 1T-TaS₂ has aroused great interest as a candidate material that hosts a QSL ground state on two-dimensional perfect triangular lattice as suggested both theoretically and experimentally[1, 2]. To study the effect of randomness on the QSL state, we performed thermal conductivity and specific heat measurements on pure, Se-doped and electron irradiated 1T-TaS₂. The results indicate the coexistence of itinerant and localized gapless spin excitations, suggesting a novel spin liquid state where itinerant quasiparticles coexist with randomly distributed orphan spins forming localized random singlets. In addition, thermal conductivity reveals the suppression of gapless spin excitations by Se-doping, indicating that the itinerant gapless spin excitations are sensitive to randomness. We will also discuss the effect of randomness on the specific heat.
[1] K. T. Law and P. A. Lee, PNAS 114, 6996 (2017).
[2] M. Klanjsek, et al., Nat. Phys. 13, 1130 (2017).