@article{hu_liu_subramanyan_li_zhou_liu_2019, title={Enhanced thermoelectric properties through minority carriers blocking in nanocomposites}, volume={126}, ISSN={["1089-7550"]}, url={http://dx.doi.org/10.1063/1.5118981}, DOI={10.1063/1.5118981}, abstractNote={We use the Boltzmann transport equation under the relaxation time approximation to investigate the effect of minority blocking on the transport properties of nanocomposites (NCs). Taking p-type Bi0.5Sb1.5Te3 NCs as an example, we find that the thermally excited minority carriers can be strongly scattered by engineered interfacial potential barriers. Such scattering phenomena suppress the bipolar effect, which is helpful to enhance the Seebeck coefficient and reduce the electronic thermal conductivity, especially at high temperatures. Further combining with the majority carriers low-energy filtering effect, the power factor and the figure of merit (ZT) can be significantly enhanced over a large temperature range from 300 K to 500 K. Such an improvement of ZT is attributed to the majority carriers low-energy filtering effect at low temperatures and to the minority carriers blocking effect at high temperatures. A principle that is helpful to provide guidance on the thermoelectric device design is identified: (1) blocking the minority carriers as often as possible and (2) filtering the majority carriers whose energy is lower than 2–3kBT near the cold end.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Hu, Jizhu and Liu, Bin and Subramanyan, Harish and Li, Baowen and Zhou, Jun and Liu, Jun}, year={2019}, month={Sep} }
 @article{subramanyan_zhang_he_kim_li_liu_2019, title={Role of angular bending freedom in regulating thermal transport in polymers}, volume={125}, ISSN={["1089-7550"]}, url={http://dx.doi.org/10.1063/1.5086176}, DOI={10.1063/1.5086176}, abstractNote={Polymers, despite their desirable structural properties, suffer from low thermal conductivity, which restricts their use. Previous studies have indicated that the strong bond-stretching and angular-bending interactions along the chain are believed to have saturated the maximum achievable thermal conductivity in the along-the-chain direction. Contrary to this belief, our results show an improvement in thermal conductivity. By increasing the bond and angle potential, we studied the effect on the thermal conductivity of polyethylene using non-equilibrium molecular dynamics simulations. In comparison to restricting the bond stretching, we found that restricting angular bending freedom plays a crucial role in improving the thermal transport along the chain. We observed significant changes in the morphology of the polyethylene chains when the angle potential was increased. We also found a remarkable increase in the phonon group velocity accompanied by large shifts in the longitudinal acoustic branch of the dispersion curve. These results when coupled with the structural changes strongly support the argument that thermal conductivity can be controlled by restricting the angular bending freedom.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Subramanyan, Harish and Zhang, Weiye and He, Jixiong and Kim, Kyunghoon and Li, Xiaobo and Liu, Jun}, year={2019}, month={Mar} }