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Search Publications by: Daniel Walkup (Assoc)

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Displaying 1 - 8 of 8

Visualizing the merger of tunably coupled graphene quantum dots

December 6, 2023
Author(s)
Daniel Walkup, Fereshte Ghahari, Steven R. Blankenship, Kenji Watanabe, Takashi Taniguchi, Nikolai Zhitenev, Joseph A. Stroscio
Coupled quantum dots have been realized in a wide variety of physical systems and have attracted interest for many different applications. Here, we examine novel graphene quantum dots in backgated devices on hBN, and visualize their merger using scanning

A quantum ruler for orbital magnetism in moire quantum matter

October 5, 2023
Author(s)
Marlou Slot, Yulia Maximenko, Paul M. Haney, Sungmin Kim, Daniel Walkup, Evgheni Strelcov, En-Min Shih, Dilek Yildiz, Steven R. Blankenship, Kenji Watanabe, Takashi Taniguchi, Yafis Barlas, Nikolai Zhitenev, Fereshte Ghahari Kermani, Joseph A. Stroscio
Topological properties that underlie the rich emergent phases of moiré quantum matter (MQM) result from the eigenstate geometry of the moiré Hamiltonian. The eigenstate geometry involves the Berry curvature and the less known quantum metric. Most studies

Edge channels of broken-symmetry quantum Hall states in graphene visualized by atomic force microscopy

May 14, 2021
Author(s)
Joseph A. Stroscio, Sungmin Kim, Johannes Schwenk, Daniel T. Walkup, Yihang Zeng, Fereshte Ghahari, Son T. Le, Marlou R. Slot, Julian Berwanger, Steven R. Blankenship, Kenji Watanabe, Takashi Taniguchi, Franz Giessibl, Nikolai Zhitenev, Cory Dean
The quantum Hall (QH) effect, a topologically non-trivial quantum phase, expanded and brought into focus the concept of topological order in physics. The topologically protected quantum Hall edge states are of crucial importance to the QH effect but have

Achieving meV tunneling resolution in an in-operando scanning tunneling microscopy, atomic force microscopy, and magnetotransport system for quantum materials research

July 6, 2020
Author(s)
Johannes Schwenk, Sungmin Kim, Julian Berwanger, Fereshte Ghahari Kermani, Daniel T. Walkup, Marlou R. Slot, Son T. Le, W. G. Cullen, Steven R. Blankenship, Sasa Vranjkovic, Hans Hug, Young Kuk, Franz Giessibl, Joseph A. Stroscio
Research in new quantum materials require multi-mode measurements spanning length scales, correlations of atomic scale variables with macroscopic function, and with an ultimate energy resolution only obtainable at ultra-low temperatures, typically in a

Tuning single-electron charging and interactions between compressible Landau level islands in graphene

January 29, 2020
Author(s)
Daniel T. Walkup, Fereshte Ghahari Kermani, Christopher Guti?rrez, Kenji Watanabe, Takashi Taniguchi, Nikolai B. Zhitenev, Joseph A. Stroscio
Interacting quantum dots (QDs), small chunks of matter with well-separated energies of electronic levels, have been extensively exploited in condensed matter physics and quantum information science. Using a low-temperature scanning tunneling microscope

Interaction-driven quantum Hall wedding cake-like structures in graphene quantum dots

August 24, 2018
Author(s)
Christopher Gutierrez, Daniel T. Walkup, Fereshte Ghahari Kermani, Cyprian Lewandowski, Joaquin R. Nieva, Kenji Watanabe, Takashi Taniguchi, Leonid Levitov, Nikolai Zhitenev, Joseph A. Stroscio
Interactions amongst relativistic particles underpin exotic behaviours in diverse systems ranging from quark-gluon plasmas to Dirac electron fluids in solids. Despite long-standing interest, direct observation of quantum-relativistic matter under ambient

Helical Level Structure of Dirac Potential Wells

November 28, 2017
Author(s)
Daniel T. Walkup, Joseph A. Stroscio
In graphene and other massless 2D Dirac materials, Klein tunneling compromises electron confinement, and momentum-space contours can be assigned a Berry phase which is either zero or π. Consequently, in such systems the energy spectrum of circular

An On/Off Berry Phase Switching with Circular Graphene Resonators

May 26, 2017
Author(s)
Fereshte Ghahari Kermani, Daniel T. Walkup, Christopher Gutierrez, Joaquin R. Nieva, Yue Y. Zhao, Jonathan E. Wyrick, Donat F. Natterer, William G. Cullen, Kenji Watanabe, Takashi Taniguchi, Leonid Levitov, Nikolai B. Zhitenev, Joseph A. Stroscio
Berry phase is an example of anholonomy, where the phase of a quantum state may not return to its original value after its parameters cycle around a closed path; instead the quantum system’s wavefunction may acquire a real measurable phase difference