Wednesday, September 18, 2019

DOE Experimental Condensed Matter PI Meeting, day 3 and wrapup

On the closing day of the PI meeting, some further points and wrap-up:

  • I had previously missed work that shows that electric field can modulate magnetic exchange in ultrathin iron (overview).
  • Ferroelectric layers can modulate transport in spin valves by altering the electronic energetic alignment at interfaces.  This can result in some unusual response (e.g., the sign of the magnetoresistance can flip with the sign of the current, implying spin-diode-like properties).
  • Artificial spin ices are still cool model systems.  With photoelectron emission microscopy (PEEM), it's possible to image ultrathin, single-domain structures to reveal their mangetization noninvasively.  This means movies can be made showing thermal fluctuations of the spin ice constituents, revealing the topological character of the magnetic excitations in these systems.  
  • Ultrathin oxide membranes mm in extent can be grown, detached from their growth substrates, and transferred or stacked.  When these membranes are really thin, it becomes difficult to nucleate cracks, allowing the membranes to withstand large strains (several percent!), opening up the study of strain effects on a variety of oxide systems.
  • Controlled growth of stacked phthalocyanines containing transition metals can generate nice model systems for studying 1d magnetism, even using conventional (large-area) methods like vibrating sample magnetometry.
  • In situ oxide MBE and ARPES, plus either vacuum annealing or ozone annealing, has allowed the investigation of the BSCCO superconducting phase diagram over the whole range of dopings, from severely underdoped to so overdoped that superconductivity is completely suppressed.  In the overdoped limit, analyzing the kink found in the band dispersion near the antinode, it seems superconductivity is suppressed at high doping because the coupling (to the mode that causes the kink) goes to zero at large doping.  
  • It's possible to grow nice films of C60 molecules on Bi2Se3 substrates, and use ARPES to see the complicated multiple valence bands at work in this system.  Moreover, by doing measurements as a function of the polarization of the incoming light, the particular molecular orbitals contributing to those bands can be identified.
  • Through careful control of conditions during vacuum filtration, it's possible to produce dense, locally crystalline films of aligned carbon nanotubes.  These have remarkable optical properties, and with the anisotropy of their electronic structure plus ultraconfined character, it's possible to get exciton polaritons in these into the ultrastrong coupling regime.
Overall this was a very strong meeting - the variety of topics in the program is impressive, and the work shown in the talks and posters was uniformly interesting and of high quality. 


DanM said...

So what did Imelda do to houses along Buffalo Speedway? Nothing bad, I hope?

Douglas Natelson said...

Nothing much, thank goodness. As you know, the national news doesn't do the greatest job of conveying how big Houston is, or how localized damage is. Areas to the N and E got hit hard. Winnie and Beaumont got something like 1m of rain.