Collective Quantum Phenomena

Within condensed matter physics, the study of 2D materials is a diverse and active field of interest with a rich history. High-quality 2DEGs in GaAs/AlGaAs heterostructure enabled the discovery of rich quantum Hall physics, including FQHE states from exotic non-Abelian many-body excitations. The recent advent of hBN-encapsulation has significantly improved the quality of the vdW materials and opens a wide range of research frontiers in studying unconventional phase of matters, such as Dirac Fluid, Luttinger liquid, and non-Abelian quantum excitations, providing new material platforms to answer many key questions in condensed matter physics. 

Quantum Hall Tunneling Spectroscopy

QHE

We report tunneling transport in spatially controlled networks of quantum Hall (QH) edge states in bilayer graphene. By manipulating the separation, location, and spatial span of QH edge states via gate-defined electrostatics, we observe resonant tunneling between copropagating QH states across incompressible strips. Employing spectroscopic tunneling measurements and an analytical model, we characterize the energy gap, width, density of states, and compressibility of the QH edge states with high precision and sensitivity within the same device. The capability to engineer the QH edge network also provides an opportunity to build future quantum electronic devices with electrostatic manipulation of QH edge states, supported by rich underlying physics.

Tunneling Spectroscopy of Quantum Hall Edge States in Gate-defined Bilayer Graphene PN Networks

K. Wang, A. Harzheim, T. Taniguchi, K. Watanabe, P. Kim

Phys. Rev. Lett, 122, 146801, (2019)

Observation of the Dirac fluid and the Breakdown of the Wiedemann-Franz law in Graphene

J. Crossno, J. Shi, K. Wang, X. Liu, A. Harzheim, A. Lucas, S. Sachdev, P. Kim, T. Taniguchi, K. Watanabe, T. Ohki, K. Fong

Science 351, 1058 (2016)