Hongkun Park
· Mark Hyman Jr. Professor of Chemistry Professor of PhysicsVerifiedHarvard University · Chemistry
Active 1990–2026
About
Hongkun Park is the Mark Hyman Jr. Professor of Chemistry and a Professor of Physics at Harvard University, located at 12 Oxford Street, Cambridge, MA. He received his B.S. degree in Chemistry from the College of Natural Sciences at Seoul National University, Korea, graduating summa cum laude and Valedictorian in 1990. After completing a year of mandatory military service in the Republic of Korea Army, he earned his Ph.D. in Chemistry from Stanford University in 1996 under the guidance of Richard N. Zare, focusing on photoionization dynamics of nitric oxide probed by angle- and energy-resolved photoelectron spectroscopy. Following his doctoral studies, he conducted a three-year postdoctoral fellowship at Lawrence Berkeley National Laboratory with Paul Alivisatos and Paul McEuen, where his research involved electron transport through nanocrystals and nanocrystal arrays. He joined Harvard's Department of Chemistry and Chemical Biology in 1999. Throughout his career, he has received numerous awards including the Camille and Henry Dreyfus New Faculty Award, the David and Lucile Packard Foundation Fellowship, the NSF-CAREER Award, the Alfred P. Sloan Research Fellowship, the NIH Director's Pioneer Award, and was elected as a Fellow of the American Association for the Advancement of Science in 2011. His research focuses on materials and physical/chemical physics.
Research topics
- Physics
- Quantum mechanics
- Materials science
- Computer Science
- Nanotechnology
- Condensed matter physics
- Engineering
- Biology
- Biological system
- Business
- Electronic engineering
- Statistical physics
- Biophysics
- Nuclear physics
- Nuclear magnetic resonance
- Chemical physics
- Chemistry
- Genetics
Selected publications
Bilayer Wigner crystals in a transition metal dichalcogenide heterostructure
Nature · 190 citations
Senior authorCorresponding- Condensed matter physics
- Materials science
- Physics
Abstract One of the first theoretically predicted manifestations of strong interactions in many-electron systems was the Wigner crystal1–3, in which electrons crystallize into a regular lattice. The crystal can melt via either thermal or quantum fluctuations4. Quantum melting of the Wigner crystal is predicted to produce exotic intermediate phases5, 6 and quantum magnetism7, 8 because of the intricate interplay of Coulomb interactions and kinetic energy. However, studying two-dimensional Wigner crystals in the quantum regime has often required a strong magnetic field9–11 or a moiré superlattice potential12–15, thus limiting access to the full phase diagram of the interacting electron liquid. Here we report the observation of bilayer Wigner crystals without magnetic fields or moiré potentials in an atomically thin transition metal dichalcogenide heterostructure, which consists of two MoSe2 monolayers separated by hexagonal boron nitride. We observe optical signatures of robust correlated insulating states at symmetric (1:1) and asymmetric (3:1, 4:1 and 7:1) electron doping of the two MoSe2 layers at cryogenic temperatures. We attribute these features to bilayer Wigner crystals composed of two interlocked commensurate triangular electron lattices, stabilized by inter-layer interaction16. The Wigner crystal phases are remarkably stable, and undergo quantum and thermal melting transitions at electron densities of up to 6 × 1012 per square centimetre and at temperatures of up to about 40 kelvin. Our results demonstrate that an atomically thin heterostructure is a highly tunable platform for realizing many-body electronic states and probing their liquid–solid and magnetic quantum phase transitions4–8, 17.
arXiv (Cornell University) · 2026-05-11
preprintOpen accessSenior authorStrong magnetic fields quench the kinetic energy of electrons, leading to the formation of flat energy bands, known as Landau levels (LLs). In this situation, even weak interactions can drive the emergence of various ordered phases. The simplest of such phases is a quantum Hall ferromagnet, where a spontaneous spin polarization emerges when LLs with opposite spins cross. The presence of strong electron-electron interaction at zero field changes this picture and makes the resulting states much harder to predict. Here we use magneto-optical spectroscopy to reveal quantum Hall states with unconventional correlations favouring an unpolarized state in the strongly correlated electron liquid in a MoSe2 monolayer. The oscillations of the exciton polaron energies as a function of perpendicular magnetic field and electron density demonstrate the emergence of LLs in a correlated electron liquid and density-dependent crossings between LLs of opposite valleys. On lowering the LL filling factor, where interactions within LLs are stronger, the crossings systematically broaden, indicating an increase in the Zeeman energy required to fully polarize the valley-degenerate LLs. These observations are shown to be consistent with antiferromagnetic interactions between LL electrons, favouring a ground state with zero valley polarization, and are therefore inconsistent with conventional quantum Hall ferromagnetism. This discovery demonstrates a qualitatively distinct form of quantum Hall magnetism in a strongly correlated electron liquid, establishing an anchoring point for understanding spin-unpolarized fractional and ordered states of correlated electrons driven by magnetic field.
ArXiv.org · 2026-05-11
articleOpen accessSenior authorStrong magnetic fields quench the kinetic energy of electrons, leading to the formation of flat energy bands, known as Landau levels (LLs). In this situation, even weak interactions can drive the emergence of various ordered phases. The simplest of such phases is a quantum Hall ferromagnet, where a spontaneous spin polarization emerges when LLs with opposite spins cross. The presence of strong electron-electron interaction at zero field changes this picture and makes the resulting states much harder to predict. Here we use magneto-optical spectroscopy to reveal quantum Hall states with unconventional correlations favouring an unpolarized state in the strongly correlated electron liquid in a MoSe2 monolayer. The oscillations of the exciton polaron energies as a function of perpendicular magnetic field and electron density demonstrate the emergence of LLs in a correlated electron liquid and density-dependent crossings between LLs of opposite valleys. On lowering the LL filling factor, where interactions within LLs are stronger, the crossings systematically broaden, indicating an increase in the Zeeman energy required to fully polarize the valley-degenerate LLs. These observations are shown to be consistent with antiferromagnetic interactions between LL electrons, favouring a ground state with zero valley polarization, and are therefore inconsistent with conventional quantum Hall ferromagnetism. This discovery demonstrates a qualitatively distinct form of quantum Hall magnetism in a strongly correlated electron liquid, establishing an anchoring point for understanding spin-unpolarized fractional and ordered states of correlated electrons driven by magnetic field.
Wideband Covariance Magnetometry below the Diffraction Limit
Physical Review Letters · 2025-09-25 · 1 citations
articleOpen accessWe experimentally demonstrate a method for measuring correlations of wideband magnetic signals with spatial resolution below the optical diffraction limit. Our technique employs two nitrogen-vacancy (NV) centers in diamond as nanoscale magnetometers, spectrally resolved by inhomogeneous optical transitions. Using high-fidelity optical readout and long spin coherence time, we probe correlated megahertz-range noise with sensitivity of 15 nTHz^{-1/4}. In addition, we use this system for correlated T_{1} relaxometry, enabling correlation measurements of gigahertz-range noise. Under such externally applied noise, while individual NV centers exhibit featureless relaxation, their correlation displays rich coherent and incoherent dynamics reminiscent of superradiance physics. This capability to probe high-frequency correlations provides a powerful tool for investigating a variety of condensed-matter phenomena characterized by nonlocal correlations.
ArXiv.org · 2025-03-18
preprintOpen accessElectronic spins of nitrogen vacancy (NV) centers in diamond constitute a promising system for micro- and nano-scale magnetic sensing, due to their operation under ambient conditions, ease of placement in close proximity to sensing targets, and biological compatibility. At high densities, the electronic spins interact through dipolar coupling, which typically limits but can also potentially enhance sensing performance. Here we report the experimental demonstration of many-body signal amplification in a solid-state, room temperature quantum sensor. Our approach utilizes time-reversed two-axis-twisting interactions, engineered through dynamical control of the quantization axis and Floquet engineering in a two-dimensional ensemble of NV centers. Strikingly, we observe that the optimal amplification occurs when the backward evolution time equals twice the forward evolution time, in sharp contrast to the conventional Loschmidt echo. These observations can be understood as resulting from an underlying time-reversed mirror symmetry of the microscopic dynamics, providing key insights into signal amplification and opening the door towards entanglement-enhanced practical quantum sensing.
Nature Biomedical Engineering · 2025-02-11 · 15 citations
articleOpen accessNetwork intracellular recording and synaptic connection mapping with a microhole electrode array
VTechWorks (Virginia Tech) · 2025-11-15
articlePatch-clamp electrodes capture intracellular signals from few neurons, while microelectrode arrays (MEAs) record many neurons extracellularly with limited sensitivity. Bridging these approaches has been a long-standing goal. We report a 4,096-channel semiconductor microhole electrode array that records intracellularly from thousands of neurons in parallel. From over 2,000 neurons, more than 70,000 plausible synaptic connections were identified and classified as electrical, inhibitory, or excitatory, with about 5% error. This platform enables large-scale mapping of neuronal network connectivity with single-cell resolution.
Universal distributed blind quantum computing with solid-state qubits
Science · 2025-05-01 · 21 citations
articleBlind quantum computing is a promising application of distributed quantum systems, in which a client can perform computations on a remote server without revealing any details of the applied circuit. Although the most promising realizations of quantum computers are based on various matter-qubit platforms, implementing blind quantum computing on matter qubits remains a challenge. Using silicon-vacancy (SiV) centers in nanophotonic diamond cavities with an efficient optical interface, we demonstrated a universal quantum gate set consisting of single- and two-qubit blind gates over a distributed two-node network. Using these ingredients, we performed a distributed algorithm with blind operations across our two-node network, proving a route to develop blind quantum computation with matter qubits in distributed, modular architectures.
Dressed-state Hamiltonian engineering in a strongly interacting solid-state spin ensemble
ArXiv.org · 2025-12-09
preprintOpen accessIn quantum science applications, ranging from many-body physics to quantum metrology, dipolar interactions in spin ensembles are controlled via Floquet engineering. However, this technique typically reduces the interaction strength between spins, and effectively weakens the coupling to a target sensing field, limiting the metrological sensitivity. In this work, we develop and demonstrate a method for direct tuning of the native interaction in an ensemble of nitrogen-vacancy (NV) centers in diamond. Our approach utilizes dressed-state qubit encoding under a magnetic field perpendicular to the crystal lattice orientation. This method leads to a $3.2\times$ enhancement of the dimensionless coherence parameter $JT_2$ compared to state-of-the-art Floquet engineering, and a $2.6\times$ ($8.3~$dB) enhanced sensitivity in AC magnetometry. Utilizing the extended coherence we experimentally probe spin transport at intermediate to late times. Our results provide a powerful Hamiltonian engineering tool for future studies with NV ensembles and other interacting higher-spin ($S>\frac{1}{2}$) systems.
Physical Review Letters · 2025-01-27 · 10 citations
articleSenior authorA mirror twin boundary (MTB) in a transition metal dichalcogenide monolayer can host one-dimensional electron liquid of a topological nature with tunable interactions. Unfortunately, electrical characterization of such boundaries has been challenging due to the paucity of samples with large enough size and high quality. Here, we report the conductance measurements of individual MTBs in epitaxially grown monolayer molybdenum disulfide bicrystals that are tens of micrometers long. These MTBs exhibit power-law behaviors of conductance as a function of temperature and bias voltage up to room temperature, consistent with electrons tunneling into a Luttinger liquid. Transport measurements of two distinct types of MTBs reveal the critical role of the atomic-scale defects. This study demonstrates that MTBs in transition metal dichalcogenide monolayers provide an exciting new platform for studying the interplay between electronic interactions and topology.
Recent grants
NIH · $3.3M · 2013
NSF · $1.3M · 2002–2007
NIH · $832k · 2013
Frequent coauthors
- 137 shared
Mikhail D. Lukin
Harvard University
- 59 shared
Philip Kim
Delft University of Technology
- 51 shared
Giovanni Scuri
- 51 shared
Takashi Taniguchi
- 49 shared
Aviv Regev
Broad Institute
- 48 shared
Kenji Watanabe
National Institute for Materials Science
- 41 shared
You Zhou
State Key Laboratory of Automotive Simulation and Control
- 40 shared
Marko Lončar
Labs
Education
- 2014
Ph.D., Chemistry
Harvard University
- 2009
B.S., Chemistry
Seoul National University
Awards & honors
- Camille and Henry Dreyfus New Faculty Award (1999)
- Research Corporation Research Innovation Award (1999)
- David and Lucile Packard Foundation Fellowship for Science a…
- NSF-CAREER Award (2002)
- Alfred P. Sloan Research Fellowship (2002)
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