Abstract
A recent experiment has reported oscillations of the thermal conductivity of $\alpha$-RuCl$_3$ driven by an in-plane magnetic field that are reminiscent of the quantum oscillations in metals. At first glance, these observations are consistent with the presence of the long-sought-after spinon Fermi surface state. Strikingly, however, the experiment also reported vanishing thermal Hall conductivity coexisting with the oscillations of the longitudinal one. Such absence of the thermal Hall effect must originate from crystalline symmetries of $\alpha$-RuCl$_3$. But if the system was a traditional spinon fermi surface state, these symmetries would also necessarily prohibit the emergence of a magnetic field acting on the spinons, in stark contradiction with the presence of quantum oscillations in experiments. To reconcile these observations, we introduce a new class of symmetry enriched ``pseudoscalar" U(1) spin liquids in which certain crystalline symmetries act as a particle-hole conjugation on the spinons. The associated pseudoscalar spinon Fermi surface states allow for the coexistence of an emergent Landau quantizing magnetic field while having an exactly zero thermal Hall conductivity. We develop a general theory of these states by constructing Gutzwiller-projected wave-functions and describing how they naturally appear as U(1) spin liquids with a distinctive projective symmetry group implementation of crystalline symmetries in the fermionic parton representation of spins. We propose that the field induced quantum disordered state in $\alpha$-RuCl$_3$ descends from a pseudoscalar spinon fermi surface state that features compensated spinon-particle and spinon-hole pockets possibly located around the $M$ points of its honeycomb Brillouin zone. These points are connected via a wave-vector associated with the emergence of the competing zig-zag antiferromagnetic state.
Highlights
A recent remarkable experiment [1] has detected oscillations of the thermal conductivity of α-RuCl3 induced by an in-plane magnetic field
In the traditional spinon Fermi surface scenario [Eq (1)], the emergent orbital magnetic field is odd under these symmetries, and it would be altogether absent if these symmetries were present, in contradiction with the very presence of quantum oscillations when the external field is applied along the b axis
In this paper we have introduced the notion of pseudoscalar U(1) spin liquids employing the fermionic parton representation of spins and a class of Gutzwiller-projected trial wave functions parametrized by spinon Slater determinants
Summary
A recent remarkable experiment [1] has detected oscillations of the thermal conductivity of α-RuCl3 induced by an in-plane magnetic field. The visibility of quantum oscillations requires that ωcτ 1, and one typically expects a comparable contribution of the spinons to the oscillatory component of both κxx and κxy in the regime in which these are experimentally detectable Such clear absence of thermal Hall effect when the field is along b must be the result of symmetries of α-RuCl3 that remain unbroken throughout the range of in-plane fields that includes both the zig-zag AFM and the quantum spin liquid state. In the traditional spinon Fermi surface scenario [Eq (1)], the emergent orbital magnetic field is odd under these symmetries, and it would be altogether absent if these symmetries were present, in contradiction with the very presence of quantum oscillations when the external field is applied along the b axis. By following the ideas of PSG [37,38], it is clear that even within the pseudoscalar U (1) spin liquids, there is a large landscape of possible symmetry enriched phases realizing different PSG implementations of physical symmetries
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have