A5065661050- Diamond and Carbon-based Materials Research
- Graphene research and applications
- 2D Materials and Applications
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Quantum and electron transport phenomena
- Boron and Carbon Nanomaterials Research
- Surface and Thin Film Phenomena
- Atomic and Molecular Physics
- High-pressure geophysics and materials
- Chalcogenide Semiconductor Thin Films
- Ion-surface interactions and analysis
- Nanowire Synthesis and Applications
- Quantum Information and Cryptography
- Thermal properties of materials
- Topological Materials and Phenomena
- Superconductivity in MgB2 and Alloys
- Plasmonic and Surface Plasmon Research
- Laser-induced spectroscopy and plasma
- Physics of Superconductivity and Magnetism
- Thermal Radiation and Cooling Technologies
- Electron and X-Ray Spectroscopy Techniques
- Molecular Junctions and Nanostructures
- Quantum optics and atomic interactions
- Advanced Materials Characterization Techniques
Stanford University
2023-2024
University of California, Los Angeles
2023
Harvard University
2018-2022
Harvard University Press
2018-2020
We report on quantum emission from Pb-related color centers in diamond following ion implantation and high-temperature vacuum annealing. First-principles calculations predict a negatively charged Pb-vacancy (PbV) center split-vacancy configuration, with zero-phonon transition around 2.4 eV. Cryogenic photoluminescence measurements performed emitters nanofabricated pillars reveal several transitions, including prominent doublet near 520 nm. The splitting of this doublet, 5.7 THz, exceeds that...
Phonon polaritons in van der Waals materials reveal significant confinement accompanied with long propagation length: important virtues for tasks pertaining to the control of light and energy flow at nanoscale. While previous studies phonon have relied on relatively thick samples, here reported is first observation surface single atomic layers bilayers hexagonal boron nitride (hBN). Using antenna-based near-field microscopy, propagating mono- bilayer hBN microcrystals are imaged. monolayer...
Twisted two-dimensional van der Waals (vdW) heterostructures have unlocked a new means for manipulating the properties of quantum materials. The resulting mesoscopic moiré superlattices are accessible to wide variety scanning probes. To date, spatially-resolved techniques prioritized electronic structure visualization, with lattice response experiments only in their infancy. Here, we therefore investigate dynamics twisted layers hexagonal boron nitride (hBN), formed by minute twist angle...
Transition metal dichalcogenides have been the primary materials of interest in field valleytronics for their potential information storage, yet limiting factor has achieving long valley decoherence times. We explore dynamics four monolayer TMDCs (MoS$_2$, MoSe$_2$, WS$_2$, WSe$_2$) using ab initio calculations to describe electron-electron and electron-phonon interactions. By comparing which both omit include relativistic effects, we isolate impact spin-resolved spin-orbit coupling on...
Aluminum nanostructures are a promising alternative material to noble metal for several photonic and catalytic applications, but their ultrafast electron dynamics remain elusive. Here, we combine single-particle transient extinction spectroscopy parameter-free first-principles calculations investigate the non-equilibrium carrier in aluminum nanostructures. Unlike gold nanostructures, find sub-picosecond optical response of lithographically fabricated nanodisks be more sensitive lattice...
The electronic and structural properties of atomically thin materials can be controllably tuned by assembling them with an interlayer twist. During this process, constituent layers spontaneously rearrange themselves in search a lowest energy configuration. Such relaxation phenomena lead to unexpected novel material properties. Here, we study twisted double trilayer graphene (TDTG) using nano-optical tunneling spectroscopy tools. We reveal surprising optical contrast, as well stacking...
Single photon sources based on atomic defects in layered hexagonal boron nitride (hBN) have emerged as promising solid state quantum emitters with atom-like photophysical and optoelectronic properties. Similar to other emitters, defect-phonon coupling hBN governs the characteristic single-photon emission provides an opportunity investigate electronic structure of well their spin- charge-dependent states phonons. Here, we these questions using photoluminescence excitation (PLE) experiments at...
Color centers in diamond have emerged as leading solid-state artificial atoms for a range of quantum technologies, from sensing to networks. Concerted research activities are now underway identify new color that combine stable spin and optical properties the nitrogen vacancy (NV$^-$) with spectral stability silicon (SiV$^-$) diamond, recent identifying other group IV superior properties. In this Letter, we investigate class emitters first principles, III centers, which show be...
The three-dimensional (3D) local atomic structures and crystal defects at the interfaces of heterostructures control their electronic, magnetic, optical, catalytic, topological quantum properties but have thus far eluded any direct experimental determination. Here, we use electron tomography to determine 3D positions interface a MoS
Two-dimensional materials can be crafted with structural precision approaching the atomic scale, enabling quantum defects-by-design. These defects are frequently described as "artificial atoms" and emerging optically addressable spin qubits. However, interactions coupling of such artificial atoms each other, in presence lattice, warrants further investigation. Here we present formation molecules" solids, introducing a chemical degree freedom control optoelectronic materials. Specifically,...
Abstract Artificial atom qubits in diamond have emerged as leading candidates for a range of solid-state quantum systems, from sensors to repeater nodes memory-enhanced communication. Inversion-symmetric group IV vacancy centers, comprised Si, Ge, Sn, and Pb dopants, hold particular promise their neutrally charged electronic configuration results ground-state spin triplet, enabling long coherence above cryogenic temperatures. However, despite the tremendous interest these defects,...
Unlike the electrical conductance that can be widely modulated within same material even in deep-subwavelength devices, tuning thermal a single system or nanostructure is extremely challenging and requires large-scale device. This prohibits realization of robust on/off states switching flow currents. Here, we present theory switch based on resonant coupling three photonic resonators, analogy to field-effect electronic transistor composed source, gate, drain. As platform, capitalize extreme...
The coupling of electrons to phonons (electron-phonon coupling) is crucial for the existence various phases matter, in particular superconductivity and density waves. Here, we devise a theory that incorporates quantum geometry electron bands into electron-phonon coupling, demonstrating contributions Fubini-Study metric or its orbital selective version dimensionless constant. We apply two materials, graphene MgB$_2$ where geometric account approximately 50\% 90\% total constant, respectively....
New electron-impact ionization (EII) data are presented for neutral atomic nitrogen. The atom is treated as a 67-state system, incorporating Rydberg values up to . State-specific cross sections the first three states from published -spline results. Binary-encounter Bethe calculations have been performed remaining 64 states. These designed modeling hypersonic chemistry that occurs when space vehicle enters Earth's atmosphere beyond orbit. convolved into state-specific thermal rate...
Abstract This Progress Report explores advances and opportunities in the atomic‐scale design, fabrication, imaging of quantum materials toward creating artificial atoms solids with tailored optoelectronic properties. The authors outline an “ab initio” approach to quantitatively linking first‐principles calculations atomic patterning, setting stage for new designer nanomaterials.
The existence of a charge density wave (CDW) in transition-metal dichalcogenide (TMDC) ${\mathrm{CuS}}_{2}$ has remained undetermined since its first experimental synthesis nearly 50 years ago. Despite conflicting literature regarding low-temperature structure, there exists no theoretical investigation the phonon properties and lattice stability this material. By studying first-principles electronic structure at various temperatures, we identify temperature-sensitive soft modes which unveil...
Artificial atom qubits in diamond have emerged as leading candidates for a range of solid-state quantum systems, from sensors to repeater nodes memory-enhanced communication. Inversion-symmetric group IV vacancy centers, comprised Si, Ge, Sn and Pb dopants, hold particular promise their neutrally charged electronic configuration results ground-state spin triplet, enabling long coherence above cryogenic temperatures. However, despite the tremendous interest these defects, theoretical...
Transition metal dichalcogenides are an interesting class of low dimensional materials in mono- and few-layer form with diverse applications valleytronic, optoelectronic quantum devices. Therefore, the general nature band-edges interplay valley dynamics is important from a fundamental technological standpoint. Bilayers introduce interlayer coupling effects which can have significant impact on polarization. The combined effect spin-orbit strongly modify band structure, phonon interactions...
Abstract The far‐infrared (far‐IR) remains a relatively underexplored region of the electromagnetic spectrum extending roughly from 20 to 100 µm in free‐space wavelength. Research within this range has been restricted due lack optical materials that can be optimized reduce losses and increase sensitivity, as well by long wavelengths associated with spectral region. Here exceptionally broad Reststrahlen bands two Hf‐based transition metal dichalcogenides (TMDs) support surface phonon...
We introduce the spin dissymmetry factor, a measure of spin-selectivity in optical transition rate quantum particles. This factor is valid locally, including at material interfaces and within cavities. design numerically demonstrate an cavity with three-fold rotational symmetry that maximizes dissymmetry, thereby minimizing dephasing cavity-coupled particle. Our approach emphasizes difference between chirality nearfield reveals classical parameter for designing more efficient devices.