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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:2
UID:UW-Physics-Event-8167
DTSTART:20230223T160000Z
DTEND:20230224T000000Z
DTSTAMP:20260414T122257Z
LAST-MODIFIED:20230211T025356Z
LOCATION:5310 Chamberlin
SUMMARY:VdW heterostructures: a new route to designing quantum matters
 \, R. G. Herb Condensed Matter Seminar\, Xiameng Liu\, Princeton
DESCRIPTION:From superconductivity to fractionalized particles\, fasci
 nating phenomena arise in quantum materials due to the collective beha
 viors of electrons. These quantum effects challenge our intuition abou
 t nature and provide new opportunities for future quantum information 
 technologies. Recently\, two-dimensional materials and their heterostr
 uctures have become a leading platform for realizing new quantum state
 s of matter. Mechanically assembled layer-by-layer and held together b
 y the van der Waals (vdW) force\, vdW heterostructures break through t
 he limitations of traditional material synthesis and offer entirely ne
 w ways to create quantum matters.
\n 
\nMy talk will feature two examp
 les of designing quantum matters with vdW heterostructures. In the fir
 st example\, I will illustrate how Coulomb interactions across separat
 e atomic layers pair fermions (electrons and holes) into bosons to ach
 ieve a superfluid condensate state. Thanks to the tunability of the vd
 W platform\, we can vary the pairing strength and change the nature of
  this fermion condensate from strong coupling to weak coupling\, demon
 strating a long-sought paradigm known as the BEC-BCS crossover. In the
  second example\, I will introduce the idea of moiré band engineering
 \, where the interference between two atomic lattices—named the moir
 é pattern—defines a new periodicity and reforms electronic band str
 uctures. In twisted double bilayer graphene\, such moiré periodicity 
 creates highly-degenerate bands tunable by a perpendicular electric fi
 eld. We observed electron correlation effects\, including interaction-
 driven insulation and spontaneous symmetry breaking of spins. Their ev
 olution with the electric fields reveals their close connection with t
 he moiré band features. Finally\, I will briefly discuss applications
  of local probe techniques to uncover hidden quantum properties in vdW
  platforms and share visions of leveraging rich interplays across atom
 ic interfaces to access major themes in condensed matter physics. 
URL:https://www.physics.wisc.edu/events/?id=8167
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