Unveiling non-Kitaev interactions and field-angle dependence in topological magnon transport of $lt;i$gt;α$lt;/i$gt;-RuCl$lt;sub$gt;3$lt;/sub$gt;

Honeycomb lattice Kitaev magnets exhibit exotic magnetic properties governed by the Kitaev interaction. This study delves into <inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722125.png" baseline="-0.5" display="inline" id="mathml_M1" overflow="scroll"> <mml:mrow class="MJX-TeXAtom-ORD"><mml:mi>&#x03B1;</mml:mi></mml:mrow></math></inline-formula>-RuCl<inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722126.png" baseline="-3.5" display="inline" id="mathml_M2" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"><mml:msub><mml:mi /><mml:mn>3</mml:mn></mml:msub></mml:mrow></math></inline-formula>, a prototypical example described by effective Hamiltonians encompassing bond-dependent Kitaev interactions alongside additional terms such as the Heisenberg interaction and symmetric off-diagonal exchange interactions. These non-Kitaev terms significantly influence <inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722127.png" baseline="-0.5" display="inline" id="mathml_M3" overflow="scroll"> <mml:mrow class="MJX-TeXAtom-ORD"><mml:mi>&#x03B1;</mml:mi></mml:mrow></math></inline-formula>-RuCl<inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722128.png" baseline="-3.5" display="inline" id="mathml_M4" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"><mml:msub><mml:mi /><mml:mn>3</mml:mn></mml:msub></mml:mrow></math></inline-formula>&#x2019;s low-temperature magnetism, impacting both magnetic order and excitations. We employ spin-wave theory to elucidate the topological nature of magnetic excitations within the polarized state of <inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722129.png" baseline="-0.5" display="inline" id="mathml_M5" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mi>&#x03B1;</mml:mi></mml:mrow></math></inline-formula>-RuCl<inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722130.png" baseline="-3.5" display="inline" id="mathml_M6" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub><mml:mi /><mml:mn>3</mml:mn></mml:msub></mml:mrow></math></inline-formula> under an external magnetic field. Our focus lies on transverse magnon conductivities, specially the thermal Hall conductivity and spin Nernst coefficient. The calculations unveil a pronounced dependence of the magnitude and sign structure of the low-temperature transverse thermal conductivities on both the applied magnetic field&#x2019;s orientation and the exchange parameters within the nearest neighbor Heisenberg&#x2212;Kitaev&#x2212;Gamma&#x2212;Gamma<inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722131.png" baseline="-0.5" display="inline" id="mathml_Z-20250423090715" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"><mml:msup><mml:mi /> <mml:mo>&#x2032;</mml:mo></mml:msup></mml:mrow></math></inline-formula> <inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722132.png" baseline="-3.5" display="inline" id="mathml_M8" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mo stretchy="false">(</mml:mo><mml:mi>J</mml:mi><mml:mi>K</mml:mi><mml:mi mathvariant="normal">&#x0393;</mml:mi><mml:msup><mml:mi mathvariant="normal">&#x0393;</mml:mi><mml:mo>&#x2032;</mml:mo></mml:msup><mml:mo stretchy="false">)</mml:mo></mml:mrow></math></inline-formula> model, which govern the nature and strength of spin interactions. This theoretical framework facilitates critical comparisons with experimental observations, ultimately aiding the identification of an effective Hamiltonian for Kitaev magnets exemplified by <inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722133.png" baseline="-0.5" display="inline" id="mathml_M9" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mi>&#x03B1;</mml:mi></mml:mrow></math></inline-formula>-RuCl<inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML50722134.png" baseline="-3.5" display="inline" id="mathml_M10" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub><mml:mi /><mml:mn>3</mml:mn></mml:msub></mml:mrow></math></inline-formula>.