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DTSTAMP:20260425T044216Z
UID:68dbb99644130407128829@ist.ac.at
DTSTART:20251028T110000
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DESCRIPTION:Speaker: Marco Valentini\nhosted by Georgios Katsaros\nAbstract
 : A central challenge for quantum computing is the realization of platform
 s that can store and manipulate quantum information in a way that is intri
 nsically protected from decoherence. Here\, I lay the foundation for two a
 pproaches in graphene-based systems toward realizing decoherence-free quan
 tum information\, by proposing routes to create and manipulate non-Abelian
  anyons. The first relies on inducing superconducting correlations in chir
 al edge states\, predicted to generate topologically protected zero-energy
  modes with non-abelian statistics. Experimental efforts so far have focus
 ed on engineering interfaces between superconducting materialstypically am
 orphous metalsand semiconducting quantum Hall or quantum anomalous Hall sy
 stems. However\, the strong interfacial disorder inherent in this approach
  can prevent the formation of isolated topological modes. An appealing alt
 ernative is to use low-density flat band materials in which the ground sta
 te can be tuned between intrinsic superconducting and quantum anomalous Ha
 ll states using only the electric field effect. Here we show that rhombohe
 dral tetralayer graphene aligned to a hexagonal boron nitride substrate ho
 sts a quantized anomalous Hall state at superlattice filling =1 as well as
  a superconducting state at 3.5 at zero magnetic field. Gate voltage can a
 lso be used to actuate nonvolatile switching of the chirality in the quant
 um anomalous Hall state\, allowing\, in principle\, arbitrarily reconfigur
 able networks of topological edge modes in locally gated devices. Thermody
 namic compressibility measurements further show a topologically ordered fr
 actional Chern insulator at =2/3  also stable at zero magnetic field  enab
 ling proximity coupling between superconductivity and fractionally charged
  edge modes [1]. The second approach focuses on trapping quasiparticles in
  the quantum Hall regime\, which\, in the case of even-denominator states\
 , are predicted to host non-Abelian anyons. To this end\, we fabricated a 
 quantum point contact device with a central hole that serves as a confinem
 ent region. The structure is implemented in ultra-clean mesoscopic graphen
 e devices by patterning graphite gates using local anodic oxidation with a
 n atomic force microscope. This design enables backscattering through the 
 quantum dot defined by the hole\, as confirmed by bias spectroscopy\, whic
 h reveals characteristic Coulomb diamonds indicative of single-electron ch
 arging. Furthermore\, at high magnetic fields\, edge reconstruction favors
  the emergence of a double quantum dot with tunable interdot coupling\, pr
 oviding a building block for charge qubits.[1] Y.Choi*\, Y. Choi\,* M. Val
 entini* et al.\, Superconductivity and quantized anomalous Hall effect in 
 rhombohedral graphene Nature (2025).
LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101
 )\, ISTA
ORGANIZER:swiddman@ist.ac.at
SUMMARY:Marco Valentini: Superconductivity\, Quantum Anomalous Hall Effect\
 , and Quantum Dots in Graphene
URL:https://talks-calendar.ista.ac.at/events/6055
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