BEGIN:VCALENDAR VERSION:2.0 CALSCALE:GREGORIAN PRODID:UW-Madison-Physics-Events BEGIN:VEVENT SEQUENCE:0 UID:UW-Physics-Event-3239 DTSTART:20140213T220000Z DURATION:PT1H0M0S DTSTAMP:20260313T144249Z LAST-MODIFIED:20140206T134710Z LOCATION:4274 Chamberlin Hall SUMMARY:Engineering New Electronic States in Graphene Heterostructures : Massive Dirac Fermions\, Hofstadter’s Butterfly and the Quantum Sp in Hall Effect\, Faculty Candidate Seminar\, Benjamin Hunt\, MIT DESCRIPTION:Van der Waals heterostructures represent a new and surpris ing direction in nanoscale device engineering: we stack isolated two-d imensional crystals to create layered structures with atomic precision . The layer-by-layer assembly allows us to introduce a new design par ameter - the interlayer twist angle - which can have profound conseque nces for the engineering of electronic states based on tunable interac tions between adjacent layers. In this talk\, I will discuss recent e xperiments at MIT in which we have used a hexagonal boron nitride (hBN ) layer to modify the electronic bands of monolayer graphene in a van der Waals heterostructure\, inducing a sizable bandgap at the charge n eutrality point and imparting a mass to the normally massless Dirac ch arge carriers. The bandgap occurs only in samples in which the twist angle between the graphene and hBN crystals is small\, resulting in a long-wavelength moirA(c) that acts as a superlattice potential\; by ad justing the twist angle the bandgap can be tuned. The moirA(c) superl attice potential also allows us to study the problem of a charged part icle in a periodic potential and magnetic field aEuro" the so-called H ofstadter problem aEuro" whose theoretical solution exhibits a rare in stance of fractal behavior in a quantum-mechanical energy spectrum. \n
\nI will also discuss our recent studies of weakly-coupled g raphene-hBN heterostructures in which massless Dirac fermions in graph ene exhibit a quantum spin Hall effect\, a fascinating example of a aE urooesymmetry-protected topological phaseaEuro of which the more famil iar contemporary examples are the edge and surface states of the topol ogical insulators.
\n URL:https://www.physics.wisc.edu/events/?id=3239 END:VEVENT END:VCALENDAR