1. NUS Graduate School for Integrative Sciences and Engineering; National University of Singapore; Singapore 117456 Republic of Singapore
2. Department of Electrical and Computer Engineering; National University of Singapore; Singapore 117576 Republic of Singapore
3. Department of Physics and Centre for Computational Science and Engineering (CCSE); National University of Singapore; Singapore 117542 Republic of Singapore
4. Center for Phononics and Thermal Energy Science, School of Physical Science and Engineering; Tongji University; Shanghai 200092 P. R. China