Research
1. Quantum Information Materials
The idea of realizing and harnessing coherent quantum bits in scalable solid-state environments has attracted widespread attention in the past decade. One of the milestones in the field has been the coherent manipulation of the single nitrogen-vacancy (NV) defect spin in diamond. However, inherent difficulties in growing and controlling the lattice of C diamond pose severe limitations to the use of the NV center for scalable quantum technologies. In close collaboration with experiments, we are searching for analogs to this defect in diverse materials platforms that are technologically important and mature. We proposed a several design schemes to realize NV-analogs in carbides and nitrides, including large-metal ion vacancy complexes and strain-driven formation of spin triplet. Most recently, we are exploring completely new materials paradigms for solid-state qubits, including 2-dimensional van der Waals materials.
Recent publications
Electrical charge control of h-BN single-photon sources, Mihyang Yu, Donggyu Yim, Hosung Seo, and Jieun Lee, 2D Materials 9, 035020 (2022).
First-principles predictions of out-of-plane group-IV and V dimers as high-symmetry high-spin defects in hexagonal boron nitride, Jooyong Bhang, He Ma, Donggyu Yim, Giulia Galli, and Hosung Seo, ACS Applied Materials & Interfaces 13, 45768−45777 (2021).
Polarization and localization of single-photon emitters in hexagonal boron nitride wrinkles, Donggyu Yim , Mihyang Yu, Gichang Noh, Jieun Lee, and Hosung Seo, ACS Applied Materials & Interfaces 12, 36362 (2020).
Stark tuning of single photon emitters in hexagonal boron nitride, Gichang Noh, Daebok Choi, Jin-hun Kim, Dong-gil Im, Yoon-ho Kim, Hosung Seo, and Jieun Lee, Nano Letters 18, 4710 (2018).
Designing defect-based qubit candidates in wide-gap binary semiconductors for solid-state quantum technologies, Hosung Seo, He Ma, Marco Govoni, and Giulia Galli, Physical Review Materials 1, 075002 (2017).
Design of defect spins in piezoelectric aluminum nitride for solid-state hybrid quantum technologies, Hosung Seo, Marco Govoni and Giulia Galli, Scientific Reports 6, 20803 (2016).
Designing defect spins for wafer-scale quantum technologies, Willam F. Koehl, Hosung Seo, Giulia Galli and David D. Awschalom, MRS Bulletin 40, 1146 (2015).
2. Quantum spin dynamics
Long coherence times are key to the performance of quantum bits (qubits). In quantum computing, long spin coherence times are necessary for executing quantum algorithms with many gates. Qubits with robust coherence are also ideal systems for developing applications such as collective quantum memories and ultra-sensitive quantum sensors. Using a cluster correlation expansion method, we theoretically predict and understand the quantum decoherence dynamics of a spin qubit in a solid from first-principles. As an example of some of our recent exciting results, we showed that the Hahn-echo coherence time (T2) of electron spins associated with divacancy defects in 4H-SiC reaches 1.3 ms, one of the longest T2 times of an electron spin in a naturally isotopic crystal. Using a first-principles microscopic quantum-bath model, we identified key factors determining the unusually robust coherence. Our results point to polyatomic crystals as promising hosts for coherent qubits in the solid state. More recently, we are investigating the quantum decoherence in diverse heterogeneous and anisotropic materials environments, which were unexplored before in physics.
Recent publications
First-principles theory of extending the spin qubit coherence time in hexagonal boron nitride, Jaewook Lee, Huijin Park, and Hosung Seo, npj 2D Materials and Applications 6, 60 (2022).
Decoherence of nitrogen-vacancy spin ensembles in a nitrogen electron-nuclear spin bath in diamond, Huijin Park, Junghyun Lee, Sangwook Han, Sangwon Oh, and Hosung Seo, npj Quantum Information 8, 95 (2022).
Generalized scaling of spin qubit coherence in over 12,000 host materials, Shun Kanai, F. Joseph Heremans, Hosung Seo, Gary Wolfowicz, Christopher P. Anderson, Sean E. Sullivan, Mykyta Onizhuk, Giulia Galli, David D. Awschalom, Hideo Ohno, PNAS 119 (15), e2121808119 (2022).
Quantum guidelines for solid-state spin defects, Gary Wolfowicz, F. Joseph Heremans, Christopher P. Anderson, Shun Kanai, Hosung Seo, Adam Gali, Giulia Galli, David D. Awschalom, Nature Reviews Materials 6, 906-925 (2021).
Spin coherence in two-dimensional materials, Meng Ye, Hosung Seo, and Giulia Galli, npj Computational Materials, 5, 44 (2019).
Quantum decoherence dynamics of divacancy spins in silicon carbide, Hosung Seo, Abram L. Falk, Paul V. Klimov, Kevin C. Miao, Giulia Galli, and David D. Awschalom, Nature Communications 7, 12935 (2016).
3. Computational Physics for Energy and Electronic Materials
In this research direction, we explore the world of materials that are useful for renewable energy, multi-functional electornic and optical devices, and solid-state physical chemistry. Recent research efforts focus on understanding and prediction of novel phases of van der Waals materials, such as complex selenides and sulfides, emergent properties occuring at the correlated oxide heterostructures, and the role of point defects in enhancing conductivity of complex oxides such as BiVO4, which is one of the most promising materials systems for photo-catalytic solar-to-fuel applications.
Recent publications
Elucidating atomistic mechanisms of the formation of phase-controlled ultrathin MoTe2 films and lateral hetero-phase MoTe2 interfaces, Hyeonkyeong Kim, Jooyong Bhang, Taejoon Park, Jae-Hyun Lee, Hosung Seo,* and Youngdong Yoo,* under revision (2023).
Alexander A. Demkov, Kurt Fredrickson, Hosung Seo, and Andrew O’Hara, First-principles modeling of interface effects in oxides, in Handbook of Materials Modeling, 2nd edition, Editors: By Wanda Andreoni and Sidney Yip (Springer, 2019).
The role of point defects in enhancing the conductivity of BiVO4, Hosung Seo, Yuan Ping, and Giulia Galli, Chemistry of Materials 30 (21), 7793-7802 (2018).
Early stages of the Schottky barrier formation in sub-monolayer Pt on SrTiO3 (001), Hosung Seo and Alexander A. Demkov, Physical Review B 92, 245301 (2015).
Critical differences in the surface electronic structure of Ge(001) and Si(001): Ab initio theory and angle-resolved photoemission spectroscopy, Hosung Seo, Richard C. Hatch, Patrick Ponath, Miri Choi, Agham B. Posadas, and Alexander A. Demkov, Physical Review B 89, 115318 (2014).
Strain-induced spin state transition and superexchange in LaCoO3, Hosung Seo, Agham B. Posadas and Alexander A. Demkov, Physical Review B 86, 014430 (2012).