Ballistic thermal conductance in a three-dimensional quantum wire modulated with stub structure

Ballistic thermal conductance in a three-dimensional quantum wire with a stub structure is presented under both stress-free and hard wall boundary conditions at low temperatures. A comparative analysis for two-dimensional and three-dimensional models is made. The results show that when stress-free boundary conditions are applied, the universal quantum thermal conductance can be observed regardless of the geometry details in the limit T→0, and the behavior of the thermal conductance is qualitatively similar to that calculated by two-dimensional model. However, when hard wall boundary conditions are applied, the thermal conductance displays different behaviors in both two-dimensional and three-dimensional models.