Self-cloaking metamaterial for broadband microwave applications

Led by CNAM faculty member Prof. Stephen Anlage, University of Maryland physicists have developed a new cloaking material that can become transparent to microwave radiation with the flip of a switch. Because many wireless communication devices rely on microwaves, the new material could be used to design more efficient communications networks. The new material can be selectively tuned to respond to a wide range of microwave wavelengths, making it more versatile than many previous attempts at cloaking technology. The achievement is described in Physical Review X (2015) and featured on the Physics Department News Feed.

Direct Evidence of the Topological Kondo Insulator

First predicted in 2010 by M. Dzero, V. Galitski and colleagues, the Topological Kondo Insulator (TKI) is a fascinating realization of the 3D topological insulator state in a strongly correlated "Kondo" insulator. Samarium Hexaboride, the archetype Kondo insulator, is an ideal candidate for realizing this exotic state of matter, with hybridization between itinerant conduction electrons and localized f-electrons driving an insulating gap and metallic surface states at low temperatures. SmB₆ has been under scrutiny for over 45 years due to peculiar low temperature properties, which have only recently been suggested to arise due to the presence of topologically protected metallic surface states. In an new study led by Dr. Yasuyuki Nakajima in the Center for Nanophysics and Advanced Materials, the topological nature of metallic surface states in SmB₆ was investigated by exploiting the existance of a novel surface-born ferromagnetic state and studying its effect on ultra-low temperature magnetotransport properties. Nakajima and co-workers report evidence of one-dimensional surface transport with a quantized conductance value of e²/h originating from the chiral edge channels of ferromagnetic domain walls, providing the strongest evidence to date that topologically non-trivial surface states exist in SmB₆.

Read the recently published Letter entitled "One-dimensional edge state transport in a topological Kondo insulator" in Nature Physics (Nov 2015).

Superconductivity achieves new landmark

Researchers at the Max Planck Institute for Chemistry in Mainz, Germany, have recently confirmed a record-setting transition temperature of 203 K (-70° C) into the superconducting state of a hydrogen-based compound when it is squeezed under extreme pressures of around 150 GPa, or nearly 1.5 million atmospheres [Nature 2015]. While this result represents the culmination of a long history of searching for ultra-high-temperature superconductivity in metallic hydrogen, first predicted by Neil Ashcroft, the experimental realization blows the top off an old myth that conventional phonon-based superconductivity would be limited to much lower temperatures.

CNAM well represented at M2S Geneva 2015

Two CNAM faculty members, Profs. Rick Green and Johnpierre Paglione, were invited to give presentations at the 11th International Conference on Materials and Mechanisms of Superconductivity (M²S), which took place in Geneva, Switzerland the week of August 23-28, 2015. Prof. Greene gave a keynote address entitled "Spin fluctuations and charge order in electron-doped cuprates", while Prof. Paglione gave an invited talk entitled "Topological RPdBi half-Heusler semimetals: a new family of non-centrosymmetric magnetic superconductors." This conference, which occurs once every three years, is considered the premier conference on the topic of superconductivity. This year, over 700 scientists from 42 countries participated in the event.