About

Xuedan Ma is an Associate Professor of Materials Science and NanoEngineering at Rice University, having joined the institution in July 2024. She is also a Visiting Scholar at the Nanoscience and Technology Division in Argonne National Laboratory. Dr. Ma earned her Ph.D. in Physical Chemistry from the University of Hamburg in Germany, following her M.Sc. in Physical Chemistry from the University of Siegen, Germany, and a B.Sc. in Chemical Engineering from Shanghai Jiao Tong University, China. Her research areas include quantum optics, nanophotonics, cavity quantum electrodynamics, polariton chemistry, low-dimensional materials, semiconductors, magnetic and spintronic materials, as well as high-resolution imaging and spectroscopy of individual nano-objects. Prior to her current role, she served as a Postdoctoral Researcher at the Center for Integrated Nanotechnologies at Los Alamos/Sandia National Laboratories, and as an RD2 and RD3 Scientist at the Center for Nanoscale Materials at Argonne National Laboratory. Between 2017 and 2024, she was a CASE Fellow at the University of Chicago and an NAISE Fellow at Northwestern University.

Research topics

• Optoelectronics
• Nanotechnology
• Materials science
• Chemistry
• Crystallography
• Inorganic chemistry
• Chemical physics
• Condensed matter physics
• Physics
• Chemical engineering
• Optics
• Atomic physics

Selected publications

• Room temperature molding of amorphous dielectrics via van der Waals anisotropy at the nanoscale

  Nature Communications · 2026-05-12

  articleOpen access

  Mechanical instabilities produce periodic out-of-plane deformations, but applications remain limited by the need for elastic substrates and weak controllability. Here, we induce coherent, instability-driven buckling in both van der Waals (vdW) layers and underlying amorphous silica at room temperature, achieving precise spatial control and deterministic orientation. Electron-beam builds crystal-axis-dependent stress in α-MoO3, while simultaneously facilitating viscous flow in silica, producing sinusoidal wrinkles at subwavelength whose dimension are tunable by α-MoO3 thickness and electron dose. These wrinkles diffract light as on-chip optical gratings. We show coherent buckling across vdW heterostructures and peel off α-MoO3 post-buckling, leaving imprinted silica. Similar crystal-aligned wrinkles appear on amorphous Al2O3 and SiNx. By removing reliance on elastic substrates, this work extends the scope of instability-driven, lithography-free subwavelength patterning to CMOS-relevant dielectrics. The authors show that crystal anisotropy can guide nanoscale wrinkles on rigid chip substrates at room temperature, turning hard dielectrics into tunable, aligned patterns that diffract light and could support future on-chip photonic devices.

  PublisherDOI

• Enhanced spectral purity of WSe ₂ quantum emitters via conformal organic adlayers

  Science Advances · 2025-10-03 · 3 citations

  articleOpen access

  Quantum emitters in solid-state materials are typically embedded in the bulk of their hosts, making their electronic transitions inaccessible to surface modification. In contrast, two-dimensional materials, with their all-surface nature, offer a platform for tuning quantum emitters via chemical functionalization. Because of its semiconducting properties that enable electrical addressability, monolayer WSe 2 is a promising candidate for quantum emission, although the complex interplay between point defects and the localized strain needed to activate quantum emission leads to poor spectral purity. Here, we demonstrate that functionalizing monolayer WSe 2 with conformal adlayers of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) improves quantum emission spectral purity. Optical spectroscopy reveals that PTCDA functionalization lowers defect activation energies by 10 meV and induces a 30 nm redshift in quantum emission wavelength, while preserving the bright and dark exciton energies of monolayer WSe 2 . First-principles calculations corroborate these findings, thus providing molecular-level insight into the underlying mechanism of enhanced spectral purity.

  PublisherDOI

• Single photon emitters in van der Waals solids for quantum photonics: materials, theory and molecular-scale characterization probes

  Journal of Physics D Applied Physics · 2025-01-29 · 3 citations

  articleOpen accessSenior author

  Abstract Strong light–matter interactions in two-dimensional layered materials (2D materials) have attracted the interest of researchers from interdisciplinary fields for more than a decade now. A unique phenomenon in some 2D materials is their large exciton binding energies (BEs), increasing the likelihood of exciton survival at room temperature. It is this large BE that mediates the intense light–matter interactions of many of the 2D materials, particularly in their monolayer limit, where the interplay of excitonic phenomena poses a wealth of opportunities for high-performance optoelectronics and quantum photonics. Within quantum photonics, quantum information science (QIS) is growing rapidly, where photons are a promising platform for information processing due to their low-noise properties, excellent modal control, and long-distance propagation. A central element for QIS applications is a single photon emitter (SPE) source, where an ideal on-demand SPE emits exactly one photon at a time into a given spatiotemporal mode. Recently, 2D materials have shown practical appeal for QIS which is directly driven from their unique layered crystalline structure. This structural attribute of 2D materials facilitates their integration with optical elements more easily than the SPEs in conventional three-dimensional solid state materials, such as diamond and SiC. In this review article, we will discuss recent advances made with 2D materials towards their use as quantum emitters, where the SPE emission properties maybe modulated deterministically. The use of unique scanning tunneling microscopy tools for the in-situ generation and characterization of defects is presented, along with theoretical first-principles frameworks and machine learning approaches to model the structure-property relationship of exciton–defect interactions within the lattice towards SPEs. Given the rapid progress made in this area, the SPEs in 2D materials are emerging as promising sources of nonclassical light emitters, well-poised to advance quantum photonics in the future.

  PublisherDOI

• Theory of Excitonic States and their Fine Structure in Halide Perovskite Quantum Dots

  2025-12-15

  article
  PublisherDOI

• Near-Infrared Emission from Sulfur Heteroatom Defects in Single-Walled Carbon Nanotubes

  The Journal of Physical Chemistry C · 2025-09-19

  articleSenior authorCorresponding
  PublisherDOI

• Overcoming the surface paradox: Buried perovskite quantum dots in wide-bandgap perovskite thin films

  arXiv (Cornell University) · 2025-01-10 · 1 citations

  preprintOpen access

  Colloidal perovskite quantum dots (PQDs) are an exciting platform for on-demand quantum, and classical optoelectronic and photonic devices. However, their potential success is limited by the extreme sensitivity and low stability arising from their weak intrinsic lattice bond energy and complex surface chemistry. Here we report a novel platform of buried perovskite quantum dots (b-PQDs) in a three-dimensional perovskite thin-film, fabricated using one-step, flash annealing, which overcomes surface related instabilities in colloidal perovskite dots. The b-PQDs demonstrate ultrabright and stable single-dot emission, with resolution-limited linewidths below 130 μeV, photon-antibunching (g^2(0)=0.1), no blinking, suppressed spectral diffusion, and high photon count rates of 10^4/s, consistent with unity quantum yield. The ultrasharp linewidth resolves exciton fine-structures (dark and triplet excitons) and their dynamics under a magnetic field. Additionally, b-PQDs can be electrically driven to emit single photons with 1 meV linewidth and photon-antibunching (g^2(0)=0.4). These results pave the way for on-chip, low-cost single-photon sources for next generation quantum optical communication and sensing.

  PublisherOA PDFDOI

• Carbene Functionalization of Monolayer Tungsten Disulfide for Enhanced Quantum Emission

  ACS Nano · 2025-06-03 · 7 citations

  article

  Semiconducting two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising materials for an array of applications, ranging from conventional field-effect transistors, photodetectors, and light-emitting diodes to their more recent use in quantum photonic technologies. Chemical functionalization of 2D TMDs with organic ligands and adlayers provides an additional means for customizing their electronic and optical properties. While many pathways have been reported for the chemical functionalization of 2D TMDs, their frequent reliance on solution-based methods results in limited control over adlayer thickness and coverage, thus hindering utility in high-performance applications. Here we describe the vapor-phase functionalization of a 2D TMD with carbene ligands, specifically tungsten disulfide (WS2) with N-heterocyclic carbenes (NHCs), resulting in molecularly smooth, thin, and uniform adlayers. Reacting NHCs with monolayer WS2 reduces the broad photoluminescence background observed at cryogenic temperatures by 58%, which facilitates the detection of single-photon emitters from strained monolayer WS2, as indicated by second order correlation values (g(2)) as low as 0.17 ± 0.07. Chemical characterization coupled with density functional theory calculations suggests that the NHC adlayer has a dual defect-passivation and doping effect on monolayer WS2 that results in enhanced single-photon emission. Overall, this study establishes vapor-phase carbene functionalization as a homogeneous surface modification scheme for tailoring the quantum emission properties of semiconducting 2D TMDs.

  PublisherDOI

• Synthesis of Large-Area Crystalline Few-Layer γ-Graphyne Films at a Liquid/Liquid Interface

  ChemRxiv · 2025-06-11 · 1 citations

  preprintOpen access

  Here we report the synthesis of macroscopic films of multilayer or few-layer γ-graphyne, an sp1/sp2 allotrope of carbon, through cross-coupling 2D polymerization at a liquid/liquid interface. By adjusting the hydrophilicity of the palladium cross-coupling catalyst, we could control the thickness and morphology of these films. This interfacial synthesis method yielded γ-graphyne with fewer defects than our previously reported homogeneous batch synthesis and allowed for creating crystalline, micron-scale films of single-layer and few-layer γ-graphyne. Furthermore, we observed that the stacking of γ-graphyne pro-duced in interfacial reactions was more orderly than that produced in batch syntheses.

  PublisherOA PDFDOI

• Ultrafast Dynamics of Plasmon-Coupled Excitons in Semiconducting Nanoplatelets

  The Journal of Physical Chemistry C · 2025-04-11

  article

  Exciton-plasmon coupling in nanomaterials produces many relevant phenomena for photonics applications including increased light-matter interactions, enhanced radiative rates of quantum emitters, and coherent energy exchange. In the case of exciton coupling to surface plasmon polaritons (SPPs), dispersive interactions controlled by the wavevector of optical excitation create the opportunity for tunable optical emission. Strong temporal impacts on exciton lifetimes can also occur in coupled systems, creating the opportunity for ultrafast control of exciton lifetime via changes in electronic coupling magnitude to a dispersive SPP. The coupling strength can be impacted by the morphology of the nanomaterials. Here, we utilize colloidal semiconductor nanoplatelets deposited onto thin silver plasmonic films, and compare the results to semiconductor quantum dots deposited on the silver films. We map the dispersion of the coupled systems and measure the ultrafast transient absorption response of the coupled systems. Due to the larger interaction areas of the nanoplatelets that lie flat on the silver films, a greater degree of coupling is found for the nanoplatelets, and much faster temporal responses are found as compared to quantum dots. Fresnel theory calculations that incorporate heavy and light hole features can reproduce the dispersion of the nanoplatelet-silver film, and a simple three-state model is developed to provide insights into the nature of the coupling at different photon energies along the dispersion curve.

  PublisherDOI

• Lattice Symmetry‐Guided Charge Transport in 2D Supramolecular Polymers Promotes Triplet Formation

  Advanced Science · 2024-06-12 · 4 citations

  articleOpen accessSenior authorCorresponding

  Singlet-to-triplet intersystem crossing (ISC) in organic molecules is intimately connected with their geometries: by modifying the molecular shape, symmetry selection rules pertaining to spin-orbit coupling can be partially relieved, leading to extra matrix elements for increased ISC. As an analog to this molecular design concept, the study finds that the lattice symmetry of supramolecular polymers also defines their triplet formation efficiencies. A supramolecular polymer self-assembled from weakly interacting molecules is considered. Its 2D oblique unit cell effectively renders it as a coplanar array of 1D molecular columns weakly bound to each other. Using momentum-resolved photoluminescence imaging in combination with Monte Carlo simulations, the study found that photogenerated charge carriers in the supramolecular polymer predominantly recombine as spin-uncorrelated carrier pairs through inter-column charge transfer states. This lattice-defined recombination pathway leads to a substantial triplet formation efficiency (≈60%) in the supramolecular polymer. These findings suggest that lattice symmetry of micro-/macroscopic structures relying on intermolecular interactions can be strategized for controlled triplet formation.

  PublisherOA PDFDOI

Recent grants

• Molecular Spin Qubits in a One-Dimensional Host

  NSF · $480k · 2019–2022

• Quantum Coherence-Controlled Chemical Reactions

  NSF · $480k · 2020–2024

Frequent coauthors

• Han Htoon

  68 shared

• Stephen K. Doorn

  Center for Integrated Nanotechnologies

  57 shared

• Nicolai F. Hartmann

  Attocube Systems (Germany)

  42 shared

• Xinxin Li

  37 shared

• Jia‐Shiang Chen

  Argonne National Laboratory

  36 shared

• Daoyuan Wang

  University of Arkansas at Pine Bluff

  25 shared

• Fa‐Qian Liu

  Sun Yat-sen University

  25 shared

• Ping Peng

  University of Shanghai for Science and Technology

  25 shared

Labs

• Ma LabPI

Awards & honors

• CASE Fellow at the University of Chicago (2017-2024)
• NAISE Fellow at Northwestern University (2017-2024)