About

Diana Qiu is an Assistant Professor of Materials Science at Yale University, with additional appointments in Applied Physics. She holds a Ph.D. from the University of California, Berkeley, and a B.Sc. from Yale University. Her research focuses on engineering and tuning quantum degrees of freedom in materials to discover new properties and phenomena, as well as to harness the flow of energy, charge, and information. Her group uses and develops first principles quantum physics methods, leveraging high-performance computing to calculate many-electron interaction effects and make accurate predictions about real materials. Her work involves the discovery and design of highly-tunable, transient materials, and explores fundamental processes such as exciton transport, coherence, and nonlinear optical responses in materials relevant to optoelectronics, quantum information, and energy research. Her research interests include two-dimensional materials, heterostructures, material defects, hybrid perovskites, and topological materials.

Research topics

• Physics
• Materials science
• Molecular physics
• Chemistry
• Nanotechnology
• Computer Science
• Quantum mechanics
• Artificial Intelligence
• Engineering
• Mathematics
• Computational physics
• Condensed matter physics
• Statistical physics
• Computational chemistry
• Management science
• Crystallography
• Optoelectronics
• Optics
• Data science

Selected publications

• Data for: Isostructural electronic transition in MoS2 probed by solid-state high harmonic generation spectroscopy

  DRYAD · 2026-02-12

  datasetOpen access

  Studying materials under extreme pressure in diamond anvil cells (DACs) is key to discovering emergent states of matter, yet no method currently allows the direct measurement of the electronic structure in this environment. Solid-state high harmonic generation (sHHG) offers a unique all-optical window into the electronic structure of materials. We demonstrate sHHG spectroscopy inside a DAC by probing 2𝑯-MoS2, up to 30 GPa, revealing a pressure-induced crossover of the lowest direct bandgap from the K-point to the 𝚪-point. This transition manifests as a sharp minimum in harmonic intensity and a 30° rotation of the sHHG polarization anisotropy, despite the absence of a structural phase change. First principles simulations attribute these features to interference between competing excitation pathways at distinct points in the Brillouin zone. Our results establish sHHG as a sensitive probe of electronic transitions at high pressure, enabling access to quantum phenomena that evade detection by conventional techniques. This data repository contains materials and codes for the associated publication in Science Advances titled "Isostructural electronic transition in MoS2 probed by solid-state high harmonic generation spectroscopy" DOI: 10.1126/sciadv.adz5621

  PublisherDOI

• Driving Floquet physics with excitonic fields

  Nature Physics · 2026-01-19 · 3 citations

  article
  PublisherDOI

• Exciton-Defect Interaction and Optical Properties from a First-Principles T-Matrix Approach

  Nano Letters · 2026-01-13

  articleOpen accessCorresponding

  Understanding exciton-defect interactions is critical for optimizing optoelectronic and quantum information applications in many materials. However, ab initio simulations of material properties with defects are often limited to high defect density. Here, we study effects of exciton-defect interactions on optical absorption and photoluminescence spectra in monolayer MoS2 using a first-principles T-matrix approach. We demonstrate that exciton-defect bound states can be captured by the disorder-averaged Green’s function with the T-matrix approximation and further analyze their optical properties. Our approach yields photoluminescence spectra in good agreement with experiments and provides a new, computationally efficient framework for simulating optical properties of disordered 2D materials from first-principles.

  PublisherDOI

• Direct Observation of Massless Excitons and Linear Exciton Dispersion

  ArXiv.org · 2025-02-27

  preprintOpen accessSenior author

  Excitons -- elementary excitations formed by bound electron-hole pairs -- govern the optical properties and excited-state dynamics of materials. In two-dimensions (2D), excitons are theoretically predicted to have a linear energy-momentum relation with a non-analytic discontinuity in the long wavelength limit, mimicking the dispersion of a photon. This results in an exciton that behaves like a massless particle, despite the fact that it is a composite boson composed of massive constituents. However, experimental observation of massless excitons has remained elusive. In this work, we unambiguously experimentally observe the predicted linear exciton dispersion in freestanding monolayer hexagonal boron nitride (hBN) using momentum-resolved electron energy-loss spectroscopy. The experimental result is in excellent agreement with our theoretical prediction based on ab initio many-body perturbation theory. Additionally, we identify the lowest dipole-allowed transition in monolayer hBN to be at 6.6 eV, illuminating a long-standing debate about the band gap of monolayer hBN. These findings provide critical insights into 2D excitonic physics and open new avenues for exciton-mediated superconductivity, Bose-Einstein condensation, and high-efficiency optoelectronic applications.

  PublisherOA PDFDOI

• Optical Absorption Spectroscopy Probes Water Wire and Its Ordering in a Hydrogen-Bond Network

  Physical Review X · 2025-03-05 · 5 citations

  articleOpen access

  Water wires, quasi-one-dimensional chains composed of hydrogen-bonded (H-bonded) water molecules, play a fundamental role in numerous chemical, physical, and physiological processes. Yet direct experimental detection of water wires has been elusive so far. Based on advanced many-body theory that includes electron-hole interactions, we report that optical absorption spectroscopy can serve as a sensitive probe of water wires and their ordering. In both liquid and solid water, the main peak of the spectrum is discovered to be a charge-transfer exciton. In water, the charge-transfer exciton is strongly coupled to the H-bonding environment where the exciton is excited between H-bonded water molecules with a large spectral intensity. In regular ice, the spectral weight of the charge-transfer exciton is enhanced by a collective excitation occurring on proton-ordered water wires, whose spectral intensity scales with the ordering length of water wire. The spectral intensity and excitonic interaction strength reaches its maximum in ice XI, where the long-range ordering length yields the most pronounced spectral signal. Our findings suggest that water wires, which widely exist in important physiological and biological systems and other phases of ice, can be directly probed by this approach.

  PublisherDOI

• Moiré-controllable exciton localization and dynamics through spatially-modulated inter- and intralayer excitons in a MoSe2/WS2 heterobilayer

  Nature Communications · 2025-12-11 · 2 citations

  articleOpen accessSenior author

  Moiré heterobilayers exhibiting spatially varying exciton localization that can be precisely controlled through the twist angle have emerged as exciting platforms for studying complex quantum phenomena. Here, we study the exciton landscape in MoSe2/WS2 heterobilayers through synergistic first-principles GW plus Bethe Salpeter equation (GW-BSE) calculations and complementary time- and angle-resolved photoemission spectroscopy (tr-ARPES). We find that the MoSe2/WS2 heterobilayer has a type I band alignment at large twist angles. In contrast, at small twist angles, there exist simultaneous spatially modulated regions of local type I band alignment, hosting bright intralayer excitons, and local type II band alignment, hosting long-lived interlayer excitons, due to lattice reconstruction in different high-symmetry regions. In tr-ARPES this manifests in the observation of long-lived excitons with electron population in only MoSe2 at large twist angles, while in samples with small twist angles, signals from two distinct long-lived exciton states with electron population in both layers are observed. Contrary to earlier studies, we find no excitonic hybridization near the low-energy absorption peaks in MoSe2/WS2, whose splitting can, instead, be explained by the lattice reconstruction. Here, the authors reveal how twisting MoSe2/WS2 layers controls exciton behaviour. Combining theory and ultrafast spectroscopy, they show that lattice reconstruction creates distinct bright and long-lived excitons without hybridization effects.

  PublisherOA PDFDOI

• Isostructural electronic transition in MoS$_2$ probed by solid-state high harmonic generation spectroscopy

  ArXiv.org · 2025-06-17

  preprintOpen access

  Studying materials under extreme pressure in diamond anvil cells (DACs) is key to discovering new states of matter, yet no method currently allows the direct measurement of the electronic structure in this environment. Solid-state high harmonic generation (sHHG) offers a new all-optical window into the electronic structure of materials. We demonstrate sHHG spectroscopy inside a DAC by probing $2H$-MoS$_2$, up to 30 GPa, revealing a pressure-induced crossover of the lowest direct bandgap from the $\textbf{K}$-point to the $Γ$-point. This transition manifests as a sharp minimum in harmonic intensity and a 30° rotation of the sHHG polarization anisotropy, despite the absence of a structural phase change. First-principles simulations attribute these features to interference between competing excitation pathways at distinct points in the Brillouin zone. Our results establish sHHG as a sensitive probe of electronic transitions at high pressure, enabling access to quantum phenomena that evade detection by conventional techniques.

  PublisherOA PDFDOI

• Revealing Substitutional Oxygen as the Dominant Defect in Flux-Grown Transition Metal Diselenides

  Nano Letters · 2025-09-04 · 2 citations

  article

  Advancing both the fundamental understanding and technological application of two-dimensional semiconducting transition metal dichalcogenides (TMDs) hinges on precise control and identification of atomic-scale defects. Although self-flux growth yields exceptionally pure TMD crystals, the nature of residual defects has remained an open question. Here, we use scanning tunneling microscopy (STM) to directly image and identify point defects in both monolayer and bulk self-flux grown WSe2. We find that the dominant defects reside on chalcogen sites and are unaffected by exfoliation or oxygen exposure. Combining STM observations with first-principles simulations and bulk impurity analysis, we attribute these defects to substitutional oxygen (OSe). This finding goes against the prevailing wisdom that vacancies are the most common defects in exfoliated TMDs. By establishing substitutional oxygen as the dominant defect, our work provides a crucial reference point for interpreting structure–property relationships and informs ongoing efforts to further improve material quality and device performance.

  PublisherDOI

• Data-driven Low-rank Approximation for Electron-hole Kernel and Acceleration of Time-dependent GW Calculations

  ArXiv.org · 2025-02-08

  preprintOpen accessSenior author

  Many-body electron-hole interactions are essential for understanding non-linear optical processes and ultrafast spectroscopy of materials. Recent first principles approaches based on nonequilibrium Green's function formalisms, such as the time-dependent adiabatic GW (TD-aGW) approach, can predict the nonequilibrium dynamics of excited states including electron-hole interactions. However, the high dimensionality of the electron-hole kernel poses significant computational challenges for scalability. Here, we develop a data-driven low-rank approximation for the electron-hole kernel, leveraging localized excitonic effects in the Hilbert space of crystalline systems. Through singular value decomposition (SVD) analysis, we show that the subspace of non-zero singular values, containing the key information of the electron-hole kernel, retains a small size even as the k-grid grows, ensuring computational feasibility with extremely dense k-grids for converged calculations. Utilizing this low-rank property, we achieve at least 95% compression of the kernel and an order-of-magnitude speedup of TD-aGW calculations. Our method, rooted in physical interpretability, outperforms existing machine learning approaches by avoiding intensive training processes and eliminating time-accumulated errors, providing a general framework for high-throughput, nonequilibrium simulation of light-driven dynamics in materials.

  PublisherOA PDFDOI

• Exciton-defect interaction and optical properties from a first-principles T-matrix approach

  ArXiv.org · 2025-05-21

  preprintOpen access

  Understanding exciton-defect interactions is critical for optimizing optoelectronic and quantum information applications in many materials. However, ab initio simulations of material properties with defects are often limited to high defect density. Here, we study effects of exciton-defect interactions on optical absorption and photoluminescence spectra in monolayer MoS2 using a first-principles T-matrix approach. We demonstrate that exciton-defect bound states can be captured by the disorder-averaged Green's function with the T-matrix approximation and further analyze their optical properties. Our approach yields photoluminescence spectra in good agreement with experiments and provides a new, computationally efficient framework for simulating optical properties of disordered 2D materials from first-principles.

  PublisherOA PDFDOI

Recent grants

• CAREER: Real-Time First-Principles Approach to Understanding Many-Body Effects on High Harmonic Generation in Solids

  NSF · $435k · 2024–2029

• Ab Initio Downfolding Approach to Exciton-Continuum

  NSF · $375k · 2021–2025

Frequent coauthors

• Steven G. Louie

  Lawrence Berkeley National Laboratory

  122 shared

• Felipe H. da Jornada

  Stanford University

  75 shared

• Jeffrey B. Neaton

  University of California, Berkeley

  52 shared

• Yang‐Hao Chan

  Institute of Atomic and Molecular Sciences, Academia Sinica

  42 shared

• Sivan Refaely‐Abramson

  Weizmann Institute of Science

  27 shared

• Jonah B. Haber

  18 shared

• Kedar Hippalgaonkar

  Agency for Science, Technology and Research

  15 shared

• Zhenglu Li

  University of Southern California

  15 shared

Education

• Ph.D., Physics

  University of California

  2017

Awards & honors

• Presidential Early Career Award for Scientists and Engineers…
• NSF Faculty Early Career Development Program (CAREER) Award,…
• Packard Fellowship for Science and Engineering, 2021
• DOE Early Career Award, 2021
• Rising Stars in Physics, 2018