خواص الكتروني و توپولوژيكي گرافين دو لايه چرخيده

Electronic an‎d topological properties of twisted bilayer graphene

فيزيك

This dissertation investigates the topological, electronic, an‎d transport properties of twisted bilayer graphene. The structure of the work is organized into three parts: the introduction, which provides the historical background; the preliminary chapters, which present the basic concepts an‎d methods; an‎d the main part, which focuses on transport signatures of massless Dirac fermions in inhomogeneous structures with tilted Dirac cones. The findings show that the tilt of Dirac cones represents an emergent spacetime geometry encoded in the system’s metric. In the presence of a sigmoidal tilt profile, electronic waves exhibit behaviors analogous to gravitational redshift an‎d blueshift: the oscillation wavelength becomes shorter in regions with stronger tilt an‎d longer in regions with weaker tilt. This process occurs with minimal reflection, allowing nearly complete transmission of electronic waves. Beyond its fundamental significance as a laboratory analogue of general relativistic effects, the phenomenon also holds potential for practical applications in electronic an‎d spintronic devices. Recent experimental evidence of tilt induced by spin–orbit coupling in topological insulators provides a promising platform to implement spatially varying tilt profiles. Accordingly, this study demonstrates that certain aspects of underlying spacetime geometry can be probed within solid-state systems.

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