Theoretical Studies in Quantum Science at UCI

The Eddleman Quantum Institute at UCI has a concentrated effort on theoretical studies in the area of quantum simulations particularly with correlated materials and systems containing the rare-earth metals. There is both breadth and depth in the theory effort with a continuum of methods that allow analysis ranging from weakly correlated to strongly correlated solid state materials as well as molecular complexes. The theoretical studies span fundamental development of theory as well as detailed studies of specific real materials.

UCI is especially strong in computer simulation of quantum systems. An overview of the simulation landscape at UCI is shown to the left.

In the strongly entangled regime (upper left part of the diagram), the White group utilizes the Density Matrix Normalization Group (DMRG), which was invented at UCI by Steve White. White’s group does both applied DMRG studies, such as studies of exotic rare earth quantum magnetic materials with the Chernyshev group, and developmental work aimed to improve the capabilities of DMRG methods. In the large system/chemically realistic regime (lower right), the Wu group uses Density Functional Theory (DFT) to study a wide variety of materials and nano-devices, including rare-earth systems, collaborating with a variety of experimental groups. The Burke group is a leading group in the development of DFT theory and methods, and also applies machine learning to DFT. The Furche group spans the broad middle of the diagram, using and developing a variety of techniques, especially DFT and the Random Phase Approximation (RPA). The Furche group collaborates closely with the Evans group in simulating rare-earth quantum magnets. The Yu group studies the materials properties of the qubits used in quantum computers, determining how noise and decoherence arise from surface impurities.

UCI also has a strong theory effort in understanding the exotic quantum phases that occur in quantum materials. The Chernyshev group focuses on quantum magnetism, including highly entangled phases such as quantum spin liquids, especially in solids containing rare earth elements. The Romhanyi group focuses on the interplay of spin, orbital, and lattice degrees of freedom which can lead to exotic quantum properties, particularly in transition metal and rare-earth based quantum magnets. The Sodemann group studies the emergent fractionalized particles that can occur in exotic quantum states of matter, and how to control the collective properties of quantum systems that can lead to develop novel technological devices.

There is an extensive amount of collaboration at UCI as shown by the diagram to the left.

Individual descriptions of the theory groups at UCI are given below.

The Burke group

The Burke group develops and extends density functional theory for simulations of quantum materials and quantum chemistry. They have developed some of the world’s most accurate approximations for heavier atoms, plus methods for improving DFT calculations of transition metal complexes. Their tools provide the approximations underlying many simulations in materials science and chemistry, most recently using machine learning.

“Fitting a round peg into a round hole: asympotically correcting the generalized gradient approximation for correlation” Antonio Cancio, Guo P. Chen, Brandon T. Krull and Kieron Burke, The Journal of Chemical Physics 149, 084116 (2018).

“Benchmarks and Reliable DFT Results for Spin Gaps of Small Ligand Fe(II) Complexes” Suhwan Song, Min-Cheol Kim, Eunji Sim, Anouar Benali, Olle Heinonen and Kieron Burke, Journal of Chemical Theory and Computation 14, 2304-2311 (2018)

“Quantum chemical accuracy from density functional approximations via machine learning” Mihail Bogojeski, Leslie Vogt-Maranto, Mark E. Tuckerman, Klaus-Robert Müller, Kieron Burke, Nature Communications 11, 5223 (2020).

The Chernyshev group

The Chernyshev group focuses on theoretical studies of the rare-earth-based quantum magnets, in which strongly spin-orbit-coupled f-shells of the rare-earths facilitate anisotropic spin-spin interactions. Of special interest are the systems that combine the archetypal geometric frustration with strong anisotropy. The central objective is to advance understanding of the extensive family of quantum materials, which offer an unusually rich spectrum of opportunities for realizing unconventional ordered and exotic quantum-disordered phases.

“Disorder-Induced Mimicry of a Spin Liquid in YbMgGaO_{4},” Zhenyue Zhu, P. A. Maksimov, Steven R. White, and A. L. Chernyshev,* Phys. Rev. Lett. 119, 157201 (2017). *

“Topography of Spin Liquids on a Triangular Lattice,” Zhenyue Zhu, P. A. Maksimov, Steven R. White, and A. L. Chernyshev,* Phys. Rev. Lett. 120, 207203 (2018). *

“Anisotropic-exchange magnets on a triangular lattice: spin waves, accidental degeneracies, and dual spin liquids,” P. A. Maksimov, Zhenyue Zhu, Steven R. White, and A. L. Chernyshev,* Phys. Rev. X 9, 021017 (2019). *

The Furche group

The Furche research group’s research interests span quantum chemistry from formal electronic structure theory through software development to applications together with experimental groups. Recent directions include random phase approximation methods, nonadiabatic molecular dynamics, and properties of f-element compounds with unconventional electronic structure. Filipp Furche is a core contributor and co-founder of the Turbomole project.

C. J. Windorff, G. P. Chen, J. N. Cross, W. J. Evans, F. Furche, A. J. Gaunt, M. T. Janicke, S. A Kozimor, and B. L. Scott: “Identification of the Formal +2 Oxidation State of Plutonium: Synthesis and Characterization of {PuII[C5H3(SiMe3)2]3}1−” J. Am. Chem. Soc. 139 (2017), 3970–3973. doi: 10.1021/jacs.7b00706.

B. Nguyen, G. P. Chen, M. M. Agee, A. M. Burow, M. Tang, and F. Furche: “Divergence of Many-Body Perturbation Theory for Noncovalent Interactions of Large Molecules” J. Chem. Theory Comput. 16 (2020), 2258–2273. doi: 10.1021/acs.jctc.9b01176.

M. Muuronen, S. M. Parker, E. Berardo, A. Le, M. Zwijnenburg, and F. Furche: “Mechanism of Photocatalytic Water Oxidation on Small TiO 2 Nanoparticles” Chem. Sci. 8, (2017), 2179–2183. doi: 10.1039/C6SC04378J.

S. G. Balasubramani, G. P. Chen, S. Coriani, M. Diedenhofen, M. S. Frank, Y. J. Franzke, F. Furche, R. Grotjahn, M. E. Harding, C. Hättig, A. Hellweg, B. Helmich-Paris, C. Holzer, U. Huniar, M. Kaupp, A. M. Khah, S. K. Khani, T. Müller, F. Mack, B. Nguyen, S. M. Parker, E. Perlt, D. Rappoport, K. Reiter, S. Roy, M. Rückert, G. A. Schmitz, M. Sierka, E. Tapavicza, D. P. Tew, C. van Wüllen, V. K. Voora, F. Weigend, A. Wodyński, and J. M. Yu: “TURBOMOLE: Modular program suite for ab initio quantum-chemical and condensed-matter simulations” J. Chem. Phys. ESS2020 (2020), 184107. doi: 10.1063/5.0004635.

The Romhányi group

Judit Romhányi’s group relies on analytical approaches to study strongly correlated systems, focusing on transition metal and rare-earth based quantum magnets. In close collaboration with experimental colleagues, the group seeks to understand and characterize compounds in which the interplay of spin, orbital, and lattice degrees of freedom can lead to exotic properties of quantum origin. The main research includes frustrated magnets, spin-orbit systems, multiferroic materials, and topological spin excitations.

“Spin-Orbit Dimers and Noncollinear Phases in d1 Cubic Double Perovskites,” J. Romhányi, L. Balents, G. Jackeli, Phys. Rev. Lett. 118, 217202 (2017)

“Magnon spectrum of the helimagnetic insulator Cu2OSeO3,” P.Y. Portnichenko, J. Romhányi, Y.A. Onykiienko, A. Henschel, M. Schmidt, A.S. Cameron, M.A. Surmach, J.A. Lim, J.T. Park, A. Schneidewind, D.L. Abernathy, H. Rosner, Jeroen van den Brink and D.S. Inosov, Nat. Commun. 7, Article number: 10725 (2016)

“Hall effect of triplons in a dimerized quantum magnet,” J. Romhányi, K. Penc and R. Ganesh Nat. Commun. 6, Article number: 6805 (2015)

The White group

The White group focuses on development and application of the DMRG and tensor networks. White’s application work focuses on determining phase diagrams and dynamical properties of high temperature superconductors and exotic magnets. His current development work is focused on improving calculations of dynamics, and improving the application of DMRG to quantum chemistry and realistic materials.

Steven R. White, “Density Matrix Formulation for Quantum Renormalization Groups,” Phys. Rev. Lett. 69, 2863 (1992). (The PRL Milestone paper of 1992, 6500 citations to date.)

Simeng Yan, David A. Huse, and Steven R. White, “Spin-Liquid Ground State of the S = 1/2 Kagome Heisenberg Antiferromagnet”, Science 332, 1173 (2011) (Magazine cover article)

Bo-Xiao Zheng, et al, “Stripe order in the underdoped region of the two-dimensional Hubbard model,” Science 358, 1155 (2017).

The Wu group

The Wu group studies topological properties of SmB6 surface as well as rare earth and actinide atoms in oxide lattices for use as qubits. Theoretical analyses for the possibility of making exceedingly long coherence time of qubits with spin-vibration couplings was recently done. The Wu group is also in collaboration with the Ho and Evans groups in developing magnetic molecules for quantum computing, starting from (C5H5)2Ni and (C5H5)2Co.

Lei Gu, and Ruqian Wu, *“Origins of slow magnetic relaxation in single-molecule magnets”, *Phys. Rev. Lett, **125**, 117203 (2020).

Jie Li, Lei Gu, and Ruqian Wu, *“Stable giant magnetic anisotropy energy and long coherence time of uranium adatoms on defect aluminum oxide”, *Phys. Rev. B, **102**, 054406 (2020).

Gregory Czap, Peter J. Wagner, Jie Li, Feng Xue, Jiang Yao, R. Wu, and W. Ho, *“Detection of spin-vibration states in single magnetic molecules”, *Phys. Rev. Lett, **123**, 106803 (2019).

Gregory Czap, Peter J. Wagner, Feng Xue, Lei Gu, Jie Li, Jiang Yao, Ruqian Wu, and W. Ho, *“Probing and imaging spin interactions with a magnetic single-molecule sensor”*, Science, **364**, 670 (2019).

Tao Liu, Yufan Li, Lei Gu, Junjia Ding, Houchen Chang, P. A. Praveen Janantha, Boris Kalinikos, Valentyn Novosad, Axel Hoffmann, Ruqian Wu, C. L. Chien, and Mingzhong Wu, “*Nontrivial nature and penetration depth of topological surface states in SmB6 thin films*”, Phys. Rev. Lett. **120**, 207206 (2018).

The Yu group

To facilitate the realization of quantum computers, Clare Yu’s group is working on elucidating, and mitigating, the microscopic sources of noise and decoherence in superconducting qubits. For example, superconducting qubits, which are superconducting quantum interference devices (SQUIDs), are very sensitive to magnetic fields. Clare Yu’s group, together with Ruqian Wu’s group, showed that paramagnetic oxygen molecules adsorbed on the surface produce 1/f magnetic noise. Working with experimentalists, they subsequently demonstrated that this noise could be reduced up to a factor of 5 with suitable surface treatments.

J. M. Martinis, K. B. Cooper, R. McDermott, M. Steffen, M. Ansmann, K. Osborn, K. Cicak, S. Oh, D. P. Pappas, R. W. Simmonds, and C. C. Yu, “Decoherence in Josephson Qubits from Dielectric Loss,” Physical Review Letters 95, 210503-1 – 210503-4 (2005).

H. Wang, C. Shi, J. Hu, S. Han, C. C. Yu and R. Q. Wu, “Candidate Source of Flux Noise in SQUIDs: Adsorbed Oxygen Molecules,” Physical Review Letters 115, 077002 (2015).

P. Kumar, S. Sendelbach, M. A. Beck, J. W. Freeland, Z. Wang, H. Wang, C. C. Yu, R. Q. Wu, D. P. Pappas and R. McDermott, “Origin and Reduction of 1/f Magnetic Flux Noise in Superconducting Devices,” Physical Review Applied 6, 041001 (2016).

Z. Wang, H. Wang, C. C. Yu and R. Q. Wu, “Hydrogen as a source of flux noise in SQUIDs,” Rapid Communications, Physical Review B 98, 020403(R) (2018).

Professor William J. Evans, Director

Please email Ms. Jenise Shourds

jshourds@uci.edu

164 Rowland Hall

University of California, Irvine

Irvine, CA 92697-4675