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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:3
UID:UW-Physics-Event-9707
DTSTART:20260910T150000Z
DTEND:20260910T160000Z
DTSTAMP:20261008T113833Z
LAST-MODIFIED:20260903T193057Z
LOCATION:5310 Chamberlin Hall
SUMMARY:Shaping Quantum Materials with Light\, R. G. Herb Condensed Ma
 tter Seminar\, Daniel Kaplan\, Rutgers
DESCRIPTION:The richness of phases in quantum materials can be greatly
  augmented by light-matter interaction. I will present new theories of
  light-matter interaction in\, which generate new phases in 2D and cor
 related solids that are inaccessible in equilibrium. 
\nTo begin\, I w
 ill show that sliding ferroelectricity in 2D bilayers can be driven by
  using light to reshape the free energy of the bilayer stack. Employin
 g time-dependent self-consistent density functional theory\, I will co
 nnect this idea to quantum geometry\; light couples at quadratic order
  to charge fluctuations\, which play a dominant role in interlayer bon
 ding interactions of van der Waals materials. Beyond a critical thresh
 old in light intensity — set by the energy barrier between two stack
 ings — layers will slide against each other. I will use this to intr
 oduce the concept of an opto-mechanical transistor\, with direct appli
 cation to MoSe2.
\nNext\, I will show that in strongly correlated syst
 ems\, such as in charge density waves\, parametric coupling between am
 plitude and phase modes produces spatiotemporal patterns that twist an
 d wind the phase mode in space and time. I will discuss the origins of
  this phenomenon\, tracing it back from spontaneous symmetry breaking 
 in quantum materials\, to how light-matter interaction in dynamically 
 generates a coupling between modes which are de-coupled in equilibrium
  (and do not interact with light). I will discuss implications of this
  idea broadly\, demonstrating the power of parametric coupling in soli
 ds (in phonons\, and beyond).
\nTo conclude\, I will show how light-ma
 tter interaction can drive topological transitions in the recently dis
 covered stacking-tuned Z_2 material BiSb. By coupling to phonons which
  control the degree of band inversion in this system\, I will present 
 a practical example of light-driven topological phase transitions.  
\
 nThese theories present a new approach to tuning quantum materials and
  allow for exploring the vast landscape of quantum phenomena lying out
  of reach in equilibrium. 
\n
URL:https://www.physics.wisc.edu/events/?id=9707
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