Abstract
α-RuCl3 is a promising candidate material to realize the so far elusive quantum spin liquid ground state. However, at low temperatures, the coexistence of different exchange interactions couple the effective pseudospins into an antiferromagnetically zigzag (ZZ) ordered state. The low-field evolution of spin structure is still a matter of debate and the magnetic anisotropy within the honeycomb planes is an open and challenging question. Here, we investigate the evolution of the ZZ order parameter by second-order magneto-optical effects, the magnetic linear dichroism and magnetic linear birefringence. Our results clarify the presence and nature of metamagnetic transitions in the ZZ phase of α-RuCl3. The experimental observations show the presence of initial magnetic domain repopulation followed by a spin-flop transition for small in-plane applied magnetic fields (≈1.6 T) along specific crystallographic directions. In addition, using a magneto-optical approach, we detected the recently reported emergence of a field-induced intermediate phase before suppressing the ZZ order. The results disclose the details of various angle-dependent in-plane metamagnetic transitions quantifying the bond-anisotropic interactions present in α-RuCl3.
Highlights
Quantum materials with exotic spin liquid ground state properties arose a lot of interest due to their potential in both fundamental science and application in “topological" quantum computing devices[1,2]
The main quadratic MO effects in reflection are named magnetic linear dichroism (MLD) and magnetic linear birefringence (MLB)[62,73,74], which are defined for the reflection of linearly polarized light under normal incidence and depend on the difference in the diagonal components of the dielectric tensor[67]
We find the evolution of the order parameter L(T, B) to scale proportional to ðH À HcÞγ, where Hc corresponds to the critical magnetic field above which the antiferromagnetic ZZ order is suppressed and the system enters the magnetically disordered state
Summary
Quantum materials with exotic spin liquid ground state properties arose a lot of interest due to their potential in both fundamental science and application in “topological" quantum computing devices[1,2]. Mott-Hubbard insulating frustrated magnets with strong spin-orbit coupling and effective jeff = 1/2 states have been intensively studied as they are believed to be prime candidates realizing the physics of the exactly solvable Kitaev model on a honeycomb lattice[3–8]. The trihalide α-RuCl3 has attracted immense attention as the prime candidate to show Kitaev spin liquid physics since several experimental studies indicated fingerprints of dominant Kitaev interactions in this Mott-Hubbard insulating magnet[11–25], which was supported by multiple theoretical calculations[26–31]. Signatures of fractionalized excitations have been detected by various spectroscopy techniques[11,15,16,46,47], hinting towards a proximate spin–liquid behavior This has lead to a wide spreading in reported values for the possible interaction strengths and a controversial discussion on the effective spin Hamiltonian capturing the experimental observations[48].
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