in the field-induced low temperature states*

Here we discuss the implications that new magnetocaloric, thermal expansion and magnetostriction data of α-RuCl₃ single crystals have on its temperature-field phase diagram and uncover the magnetic-field dependence of an apparent energy gap Δ(H), extracted from thermal expansion measurements, that evolves when the low temperature antiferromagnetic order is suppressed. We show that, depending on how the thermal expansion data is modeled, Δ(H) can follow a cubic field dependence and remain finite at zero field, consistent with the pure Kitaev model. Our quasi-isothermal magnetocaloric effect data provides, below 1 K, unambiguous evidence for dissipative phenomena at the critical field, smoking gun for a first order phase transition. On the other hand, our results show little support for a phase transition from a quantum spin liquid to a polarized paramagnetic state above the critical field. The results are discussed in the context of possible quantum critical and QSL behavior in α-RuCl₃.