Novel Emergent States in Electronic Materials

Nick Butch (Lawrence Livermore National Laboratory)

The interactions between electrons in a material can lead to collective behavior qualitatively different from that of the constituent electrons themselves. Examples range from superconductivity to more exotic objects such as magnetic monopoles. I will discuss two cases of recent interest with rather different underpinnings. In topological insulators, the surfaces of an electrical insulator support symmetry-protected metallic states with novel properties, the most striking of which are chirality and protection against localization. I will describe efforts to grapple with the experimental challenges of isolating the conduction of surface states in the archetypal topological insulator Bi2Se3. I'll also touch on expanding the search for topological surface states in other promising materials. The interesting behavior of strongly correlated electrons derives from a complicated interplay of localized and itinerant electronic states. One of the oldest mysteries in this realm is the hidden order state of the heavy fermion superconductor URu2Si2, the nature of which remains uncertain after 25 years of study. I'll describe recent experimental developments that suggest an unusual twist: electrons may independently break the rotational symmetry of the underlying crystal lattice.

References: N. P. Butch, et al, Phys. Rev. B 81, 241301(R) (2010); arXiv:1003.2382v1. N. P. Butch, et al, Phys. Rev. B 84, 220504(R) (2011); arXiv:1109.0979v2. X. Zhang, et al, arXiv:1211.5532. N. P. Butch, et al, arXiv:1212.6238.

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