Metamaterials

Metamaterials are artificially made materials, whose properties may not exist in nature. The goal of this thrust area is to synthesize artificial structures such as superlattices and nano-composites, which demonstrate desirable transport properties for energy and electronic device applications. For example, achieving low thermal conductivity materials have enormous impact on both thermoelectrics and thermal management. Most naturally occurring materials do not possess low thermal conductivity besides other desirable properties such as high electrical conductivity, excellent mechanical stability etc. Metamaterials provide a novel route to explore the realization of contrasting properties by artificially tailoring the length scales in a system. Superlattices, (STEM images of superlattices of complex oxides are shown in the figure below) where two different materials are arranged periodically and show long range order, are good model systems to explore the limits of thermal transport. This understanding will open up the opportunity to engineer thermal and thermoelectric properties of materials by designing the structures from the bottom up.

Relevant Publications:

• B. Zhao, J. Ravichandran, “Low power microwave relaxation oscillators based on phase change oxides for neuromorphic computing”, Physical Review Applied, 11, 014020 (2019).
• Y. Liu, Z. Wang, A. S. Thind, T. Orvis, D. Sarkar, R. Kapadia, A. Y. Borisevich, R. Mishra, A. I. Khan, J. Ravichandran, “Epitaxial growth and Dielectric Characterization of Atomically Smooth 0.5Ba(Zr_0.2Ti_0.8)O₃–0.5(Ba_0.7Ca_0.3)TiO₃ thin films”, Journal of Vacuum Science and Technology A, 37, 011502 (2019). [Journal Cover]
• G. Singh-Bhalla, P. B. Rossen, G. K. Palsson, M. Mecklenburg, T. Orvis, S. Das, Y-L. Tang, S. J. Suresha, D. Yi, A. Dasgupta, D. Doennig, V. G. Ruiz, A. K. Yadav, M. Trassin, J. T. Heron, C. S. Fadley, R. Pentcheva, J. Ravichandran, R. Ramesh, “Unexpected Termination Switching and Polarity Compensation in LaAlO₃/SrTiO₃ heterostructures”, Physical Review Materials, 2, 112001(R) (2018). [Editor’s Suggestion, Rapid Communication]
• K. Luo, S. Niu, D. Shah, A. Lonkar, Y. Liu, and J. Ravichandran, “Prediction of Perovskite and Other Ternary Oxide Multilayers as Mirrors for Soft X-rays”, Materials Research Bulletin, 98, 206 (2018).
• J. Ravichandran, A. K. Yadav, R. Cheaito, P. B. Rossen, A. Soukiassian, S. J. Suresha, J. C. Duda, B. M. Foley, C-H. Lee, Y. Zhu, A. W. Lichtenberger, J. E. Moore, D. A. Muller, D. G. Schlom, P. E. Hopkins, A. Majumdar, R. Ramesh and M. A. Zurbuchen, “Crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices”, Nature Materials 13, 168-172 (2014).