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SUMMARY:Interplay of charge and structure in transition metal oxides
DTSTART:20170306T131500
DTEND:20170306T141500
DTSTAMP:20260403T235703Z
UID:014e1b8f72479f808b3ff5a9b3b9498112fbe149572609d023308ad2
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Peter B. Littlewood\, University of Chicago\, USA\nThe b
 oundary between metal and insulator remains a fruitful source of emergent 
 phenomena in materials\, ranging from oxides\, to cold atoms. Typically th
 e insulating side of this boundary is occupied by an electronic crystal (t
 hough often disordered)\, and at higher temperatures a polaronic liquid or
  bad metal. While the paradigm Hamiltonian for this transition involves on
 ly short –range electronic correlations\, in practice the transition is 
 tuned by disorder\, by screening of longer range Coulomb forces\, and by c
 oupling to the lattice.\n\nI will discuss the physics of small polarons in
  SrTiO3\, and in particular the collapse of strong Frohlich coupling with 
 increasing metallicity as the long-range Coulomb mediated interaction with
  optic phonons is screened out. SrTiO3 is an unusually good metal and an e
 nigmatic superconductor at very low carrier concentrations.\n\nWhile elect
 ric charges can be screened\, the same is not true of strain fields\, whic
 h have intrinsic long-range interactions that cannot be screened. When str
 ain fields are produced as a secondary order parameter in phase transition
 s - as for example in ferroelectrics - this produces unexpected consequenc
 es for the dynamics of order parameter fluctuations\, including the genera
 tion of a gap in what would otherwise have been expected to be Goldstone m
 odes. In some cases\, e.g. manganites and nickelates\, other intra-cell mo
 des can nonlinearly screen the order parameter\, which produces a strong s
 ensitivity of ordering to octahedral rotations\, essentially a jamming tra
 nsition. This is relevant for tuning entropic effects at phase transitions
 \, perhaps to enhance electro-caloric and magneto-electric effects. Wang e
 t al. Tailoring the nature and strength of electron–phonon interactions 
 in the SrTiO3(001) 2D electron liquid. Nature Materials (2016). DOI: 10.10
 38/NMAT4623 Elastic interactions and control of the Mott transition\, G. G
 . Guzmán-Verri\, R. T. Brierley\, P. B. Littlewood arXiv:1701.02318 Why i
 s the electrocaloric effect so small in ferroelectrics? G. G. Guzmán-Verr
 i\, P. B. Littlewood\, APL Mater. 4\, 064106 (2016)\n\nBio: Peter B. Littl
 ewood is a condensed matter theorist at the University of Chicago who is a
  Professor in Physics\, the James Franck Institute\, and the College. His 
 research interests include superconductivity and superfluids\, strongly co
 rrelated electronic materials\, collective dynamics of glasses and density
  waves in solids\, neuroscience\, and applications of materials for energy
  and sustainability.\n\nDr. Littlewood came to Chicago and to Argonne in 2
 011 after being appointed associate laboratory director of the lab’s Phy
 sical Sciences and Engineering directorate\, and served from 2014 to 2016 
 as Laboratory DIrector. He spent the previous 14 years at the University o
 f Cambridge\, where he last served as the head of the Cavendish Laboratory
  and the Department of Physics.  He began his career with almost 20 years
  at Bell Laboratories\, ultimately serving for five years as head of Theor
 etical Physics Research.\n\nDr. Littlewood holds six patents\, has publish
 ed more than 250 articles in scientific journals and has given more than 3
 00 invited talks at international conferences\, universities and laborator
 ies. He is a fellow of the Royal Society of London\, the Institute of Phys
 ics\, the American Physical Society\, and TWAS (The World Academy of Scien
 ces). He serves on advisory boards of research and education institutions 
 and other scientific organizations worldwide.  He holds a bachelor's degr
 ee in natural sciences (physics) and a doctorate in physics\, both from th
 e University of Cambridge.
LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201
STATUS:CONFIRMED
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