Ultralow-Temperature Thermal Conductivity of the Kitaev Honeycomb Magnet α−RuCl3 across the Field-Induced Phase Transition

Abstract

Recently, there have been increasingly hot debates on whether there exists a quantum spin liquid in the Kitaev honeycomb magnet α-RuCl_{3} in a high magnetic field. To investigate this issue, we perform ultralow-temperature thermal conductivity measurements on single crystals of α-RuCl_{3} down to 80 mK and up to 9 T. Our experiments clearly show a field-induced phase transition occurring at μ_{0}H_{c}≈7.5 T, above which the magnetic order is completely suppressed. The minimum of thermal conductivity at 7.5 T is attributed to the strong scattering of phonons by magnetic fluctuations. Most importantly, above 7.5 T, we do not observe any significant contribution of thermal conductivity from gapless magnetic excitations, which puts a strong constraint on the nature of the high-field phase of α-RuCl_{3}.

Thermal Conductivity of the Quantum Spin Liquid Candidate EtMe3Sb[Pd(dmit)Bourgeois-Hope1, Laliberté2, Lefrançois3 et al. 2019Phys. Rev. X559380View full textAdd to dashboardCite

“…For the Kyoto data, the residual linear term has been subtracted so that the data reflect only the phonon contribution κ ph . For comparison, thermal conductivity data for the spin liquid materials RuCl3 [14], YbMgGaO4 [15], Na3+xIr3O8 [16], and Tb2Ti2O7 [17] are also plotted. These are all insulators so the thermal conductivity is entirely phononic and is at least 20 times smaller than κ ph in the Kyoto data.…”

“…RuCl 3 , on the other hand, has recently attracted considerable attention as a Kitaev honeycomb magnet. When a field fully suppresses the zigzag magnetic order at about 7.5 T, the phonon-dominated thermal conductivity of RuCl 3 reaches a minimum because of scattering by spin excitations [14].…”

Pressure-induced dimerization and valence bond crystal formation in the Kitaev-Heisenberg magnet α−RuCl3

“…While electronic-structure calculations indicate that K is ferromagnetic in α-RuCl 3 and indeed defines the largest exchange energy scale [7,8,14,15], the debate on the minimal effective spin model and precise magnitude of the different couplings is not fully settled yet. By applying a magnetic field in the basal plane, the magnetic zigzag ground state can be suppressed [6,16,17] and the phase above this transition was identified as a quantum spin liquid, by NMR [18], thermal conductivity [19][20][21], terahertz spectroscopy [22], and neutron scattering experiments [23].Further, it was very recently shown by specific heat, magnetization, and NMR measurements [24,25] that the Néel …”

Topological thermal Hall effect for topological excitations in spin liquid: Emergent Lorentz force on the spinons

“…In the QSL regime, the deconfined spinons transport heat in the same way that the physical electrons carry charge in an electrical conductor. However, a major difficulty is that other excitations, most notably phonons, may get involved in the longitudinal thermal conductivity [6][7][8][9][10][11][12][13][14]. The quantitative contribution of spin excitations may be difficult to be extracted from the total longitudinal thermal conductivity due to the spin-phonon interaction, which is suggested to be present in many materials, especially in the ones with strong spin-orbit coupling.…”