Effect of quenched disorder on the quantum spin liquid state of the triangular-lattice antiferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>1</mml:mn><mml:mi>T</mml:mi><mml:mo>−</mml:mo><mml:msub><mml:mi>TaS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

This paper reports the effect of randomness on a quantum spin liquid state of 1T-TaS${}_{2}$ with a two-dimensional perfect triangular lattice. Systematic measurements of heat capacity and thermal conductivity in pure, Se-substituted, and electron-irradiated crystals reveal the microscopic coexistence of localized orphan spins that form random valence bonds and itinerant spinons that appear to form a Fermi surface.