BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:4
UID:UW-Physics-Event-4654
DTSTART:20171206T160000Z
DURATION:PT1H0M0S
DTSTAMP:20260419T021827Z
LAST-MODIFIED:20171205T123531Z
LOCATION:5310 Chamberlin Hall
SUMMARY:Unconventional interactions between 2D excitons and their envi
 ronment\, R. G. Herb Condensed Matter Seminar\, Dr. Andrey Klots \, Va
 nderbilt University
DESCRIPTION:Excitons and excitonic complexes (EC) are solid-state anal
 ogs of atoms and<br><br>
\nmolecules. Simple hydrogen-like states can 
 be studied using a plain Schrodinger<br><br>
\nequation. However\, whe
 n an EC is coupled to a medium with a frequency- or<br><br>
\nmomentum
 -dependent dielectric function\, "(!\; q)\, the quantum-mechanical de-
 <br><br>
\nscription of such system becomes less trivial. The _rst par
 t of this talk describes<br><br>
\na treatment of many-body states of 
 charged particles coupled to a frequency-<br><br>
\ndependent medium. 
 I will show that the problem of dynamically screened ECs<br><br>
\ncan
  be formally reduced to a simple problem of an EC in an e_ectively sta
 tic<br><br>
\nmedium. The environment's e_ective dielectric constant `
 perceived' by ECs de-<br><br>
\npends on the symmetries of EC wavefunc
 tions and their binding energies. This<br><br>
\napproach is applicabl
 e to individual electrons as well as to large many-body com-<br><br>
\
 nplexes. Predictions of environmental e_ects on EC binding were experi
 mentally<br><br>
\nveri_ed using neutral\, charged and defect-bound ex
 citons in monolayer WS2<br><br>
\nscreened by liquid\, metallic and se
 miconducting environments.<br><br>
\nIn the second part of the talk I 
 will show that coupling of excitons to some<br><br>
\nmetamaterials wi
 th momentum-dependent dielectric functions\, "(~k)\, allows cre-<br><b
 r>
\nation of ultrarelativistic excitons with high momenta. As a resul
 t of the Lorentz<br><br>
\ncontraction\, one can observe transient one
 -dimensional relativistic excitons in<br><br>
\ntwo-dimensional graphe
 ne.<br><br>
\n
URL:https://www.physics.wisc.edu/events/?id=4654
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