We developed ab-initio open quantum dynamics from density-matrix formalism, including quantum descriptions of electron-phonon, electron-electron, electron-defect scatterings, and spin-orbit couplings[1-3]. This framework can predict dynamics of quantum mechanical observables, for example carrier and spin relaxation and dephasing time accurately from first-principles [4], and determine the dominant decoherence mechanism for general solid-state systems. We are generalizing this framework for quantum transport, non-Markovian dynamics, and nonlinear optics.

Representative papers:

1. “Spin-phonon Relaxation from a Universal Ab initio Density-matrix ApproachJunqing Xu, Adela Habib Sushant Kumar,  Feng Wu, Ravishankar Sundararaman* , and Yuan Ping*Nature Communications11, 2780, (2020). arXiv: 1910.14198   UCSC News Press,  Santa Cruz Tech Beat,  ScienceDaily, Phys.Org,  SwissQuantumHub

2. “Ab initio Ultrafast Spin Dynamics in Solids”, J. Xu, A. Habib, R. Sundararamanand Y. Ping*, Physical Review B, 104, 184418, (2021). Editor’s Suggestions. Physics Magazine

3. “How Spin Relaxes and Dephases in Bulk Halide Perovskites, Junqing Xu, Kejun Li, Mayada Fadel,  Uyen N. Huynh, Jinsong Huang, Ravishankar Sundararaman*, Valy Vardeny*, and Yuan Ping*, Nature Communications, 15, 188, (2024). UWMadison Press News

4.“Giant Spin Lifetime Anisotropy and Spin-Valley Locking in Silicene and Germanene from First-Principles Density-Matrix Dynamics”, J. Xu, H. Takenaka, A. Habib, R. Sundararaman*, Y. Ping*Nano Letters21, 9594, (2021).




Point defects with unpaired spins in solids can be promising candidates for single-photon emitters and spin-qubits as fundamental building blocks in quantum information science. We study spin-defects in 2D and 3D solids as potential spin-qubits, focusing on their excited state dynamics, which determines their optical initialization and readout efficiency, and spin relaxation/decoherence mechanism.

We developed charge correction methods that can provide reliable charged defect properties for 2D systems and  general interfaces[1]. We developed methodology to compute radiative[2] and nonradiative recombination rates[3], as well as intersystem-crossing rate[2], including electron-hole and electron-phonon couplings. We then studied the environmental screening and strain effect on spin defects’ optoelectronic properties[4], from many-body perturbation theory.

Representative papers:

1. “First-principles Engineering of Charged Defects for Two-dimensional Quantum Technologies”,F. Wu, A. Galatas, R. Sundararaman, D. Rocca and Y. PingPhysical Review Materials (Rapid Communication)1, 071001(R) (2017),

2.”Intersystem Crossing and Exciton-Defect Coupling of Spin Defects in Hexagonal Boron Nitride”, Tyler Smart, Kejun Li, Junqing Xu and Yuan Ping*, npj Computational Materials 7, 59 (2021). arXiv:2009.02830

3. “Carrier Recombination Mechanism at Defects in Wide Band gap Two-dimensional Materials from First principles”, Feng WuTyler J. Smart, Junqing Xu and Yuan Ping*, Physical Review B (Rapid Communications)100, 081407(R), (2019). arXiv:1906.02354

4. Effect of Environmental Screening and Strain on Optoelectronic Properties of Two-Dimensional Quantum Defects”, Shimin Zhang, Kejun Li, Chunhao Guo, and Yuan Ping*, in press, 2D Materials (2023), preprint:



Low dimensional materials including (quantum dots, nanowires/nanotubes, 2D materials) have highly tunable optical properties and stronger electron hole interactions comparing with 3D materials. Previously we developed solving Bethe-Salpeter Equations (BSE) without explicit empty electronic states to treat e-h interactions explicitly with our coworkers [1-2].  We then optimize optical properties of materials through forming interfaces, introducing defects and surface functionalization.

We next developed theory and computational codes to study exciton recombination at finite temperature[3], and methods of including substrate screening at lattice-mismatched interfaces[4]. Recently we are developing theory for studying optical response of chiral systems[5] and nonlinear optical properties.

Representative papers:

1. “Electronic Excitations in Light Absorbers for Photoelectrochemical Energy Conversion: First Principles Calculations Based on Many Body Perturbation Theory”, Y. Ping, D. Rocca and G. Galli, Chemical Society Reviews42, 2437, (2013).

2. “Ab-initio Calculations of Absorption Spectra of Semiconducting Nanowires within Many Body Perturbation Theory”, Y. Ping, D. Rocca, D. Lu and G. Galli, Physical Review B, 85, 035316, (2012).

3. “Dimensionality and Anisotropicity Dependence of Radiative Recombination in Nanostructured Phosphorene”, Feng Wu, Dario Rocca, and Yuan Ping*, Journal of Materials Chemistry C, (Emerging Investigators themed issue), 7, 12891, (2019). Cover Art.  Preprint: arXiv:1903.11773

4. “Substrate Screening Approach for Quasi-particle Energies of Two-dimensional Interfaces with Lattice Mismatch”, Chunhao Guo, Junqing Xu, Dario Rocca, Yuan Ping*, Physical Review B, 102, 205113, (2020), Editors’ Suggestionarxiv.2007.07982 

5. “Circular Dichroism of Crystals from First Principles, Christian Multunas, Andrew Grieder, Junqing Xu,  Yuan Ping*, Ravishankar Sundararaman*, Physical Review Materials, 7, 123801, (2023), preprint:


Defects and doping can significantly modify the electronic structure, optical and carrier transport properties of transition metal oxides (TMOs). We coupled the Landau-Zener theory generalized to non-adiabatic electron transfer with kinetic Monte Carlo samplings to compute small polaron hopping mobility in doped TMOs, reveal  the fundamental mechanism that how dopants can improve polaronic conduction in TMOs. We also compute spectroscopic signatures of polaron and exciton states in TMOs.

Representative Papers:

Optical Absorption Induced by Small Polaron Formation in Transition Metal Oxides – The Case of Co3O4”, Tyler J. Smart, Tuan Anh Pham, Yuan Ping*, and Tadashi Ogitsu*, Physical Review Materials (Rapid Communications)3, 102401(R) (2019). arXiv:1909.08653

Combining Landau-Zener Theory and Kinetic Monte Carlo Sampling for Small Polaron Mobility of Doped BiVO4 from First-principles”, Feng Wu and Yuan Ping, Journal of Materials Chemistry A,  6, 20025-20036 (2018).  arXiv:1808.02507

Mechanistic Insights of Enhanced Spin Polaron Conduction in CuO through Atomic Doping”, Tyler Smart, Allison Cardiel, Feng Wu, Kyoung-Shin Choi and Yuan Ping, npj Computational Materials4, 61 (2018).

“Simultaneous Enhancements in Photon Absorption and Charge Transport of BiVO4 Photoanodes for Solar Water Splitting”, T. Kim, Y. Ping, G. Galli and K. Choi, Nature Communications, 6, 8769, (2015). (Highlighted in News of University of Chicago)

“Thermally Stable N2-intercalated WOPhotoanodes for Water Oxidation, Q. Mi, Y. Ping, Y. Li, B. Brunschwig, G. Galli, H. Gray and N. Lewis, Journal of the American Chemical Society, 134, 18318, (2012). (Highlighted in the feature article of CCI Solar)


Charge transfer and catalytic reactions at solid-liquid interfaces are important for solar-to-fuel, fuel cell and battery applications. We use DFT and GW approximations for the band alignment and charge transfer at the solid-liquid interfaces with implicit or explicit solvents; furthermore, we study surface catalytic reaction mechanisms including thermodynamic reaction free energies, kinetic barriers and reaction rates at the constant potential condition, directly comparing with experimental electrochemical Tafel plots and overpotential measurements.

Representative papers:

Ruthenium atomically dispersed in carbon outperforms platinum toward hydrogen evolution in alkaline media”, Bingzhang Lu, Lin Guo, Feng Wu, Yi Peng, Jia En Lu, Tyler J. Smart, Nan Wang, Y. Zou Finfrock, David Morris, Peng Zhang, Ning Li, Peng Gao, Yuan Ping*, and Shaowei Chen*, Nature Communications10, 631 (2019).

Modeling Heterogeneous Interfaces for Solar Water Splitting, T. Pham, Y. Ping and G.Galli, Nature Materials, 16, 401–408 (2017) 

“The Reaction Mechnism with Free Energy Barriers at Constant Potentials for the Oxygen Evolution Reaction at IrO2(110) Surface”, Y. Ping, R. Nielsen, W. Goddard III, Journal of the American Chemical Society139, 149-155, (2017).

“Energetics and Solvation Effects at the Photoanode/Catalyst Interface:Ohmic Contact versus Schottky Barrier”, Y. Ping, W. Goddard III and G.Galli, Journal of the American Chemical Society137, 5264, (2015).

“Solvation Effect on Band Edge Positions of Photocatalysts from First Principles”, Y. Ping, R. Sundararaman, and W. Goddard III, Physical Chemistry Chemical Physics, 17, 30499, (2015). (Highlighted in the feature article of Joint Center for Artificial Photosynthesis)