The quantum spin-liquid (QSL) state is currently of intense interest because it exhibits novel excitations as well as wave-function entanglement. The layered insulator RuCl3 orders as a zigzag antiferromagnet below 7 K in zero magnetic field. The zigzag order is destroyed when a magnetic field H is applied parallel to the zigzag axis a. Within the field interval (7.3, 11) Tesla, there is growing evidence that a QSL state exists. I will describe the emergence of oscillations in its thermal conductivity below 4 K. The oscillation amplitude is very large within the field interval (7.3, 11) T and strongly suppressed on either side. Paradoxically, the oscillations are periodic in 1/H, analogous to quantum oscillations in metals, even though RuCl3 is an excellent insulator. The implications of the oscillations are discussed.