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UID:e3f15972-490b-420a-a9db-c528005a91fb@nexttoyou
DTSTAMP:20261106T172150Z
DTSTART:20261112T200000Z
DTEND:20261112T213000Z
SUMMARY:Condensed Matter Seminar
LOCATION:Allen Hall 321\, 3941 O'Hara Street\, Pittsburgh\, PA 15213
DESCRIPTION:Hofstadter Hyperorbit Quantization of Landau Levels in twisted
 -Moiré Systems and Beyond\n\nDr. Dengyu Yang\nNational Institute for Stan
 dards and Technology (NIST)\n\nAbstract: The Hofstadter butterfly is a st
 riking quantum fractal: the energy spectrum of two-dimensional electrons 
 moving through a periodic potential in a magnetic field. Its intricate st
 ructure connects quantum physics with number theory\, with successive gen
 erations of spectral features organized by the Farey tree of rational num
 bers. Graphene moiré superlattices bring this physics within reach of lab
 oratory magnetic fields\, enabling electrical transport measurements to r
 eveal topological gaps and their associated quantized Hall conductivities
 . However\, transport does not directly resolve the energy bands that for
 m the butterfly’s recursive structure. In this talk\, I will present scan
 ning tunneling spectroscopy measurements of a bilayer graphene–hexagonal 
 boron nitride (hBN) moiré superlattice that resolve parent magnetic Bloch
  bands and their offspring\, revealing the Farey-tree hierarchy in the el
 ectronic spectrum. I will also discuss our semiclassical analysis connect
 ing the parent bands to their offspring through the quantization of Hofst
 adter hyperorbits. This analysis highlights the role of quantum geometry\
 , through Berry curvature and the associated orbital magnetic moment\, in
  determining hyperorbit energies. Together\, these results connect the ma
 thematical organization of the Hofstadter butterfly to the physi\n\nhttp:
 //next-to-u.app/events/e3f15972-490b-420a-a9db-c528005a91fb
URL:http://next-to-u.app/events/e3f15972-490b-420a-a9db-c528005a91fb
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