FY2019 Annual Report
Theory of Quantum Matter Unit
Professor Nic Shannon
Abstract
FY2019 was an unusual, but none the less productive, year for OIST's Theory of Quantum Matter (TQM) Unit. The year began with Prof. Shannon on Sabbatical in Munich, and ended with all travel and scientific events being cancelled as result of the COVID19 pandemic.
The TQM Unit welcomed a new PhD student, Ms Leilee Chojnacki, and celebrated Dr Judit Romhanyi moving on to a faculty position at the University of California, Irvine. Meanwhile Han Yan successfully defended his PhD Thesis, and was awarded OIST's inaugural Award for Student Excellence in Graduate Research. The Unit was also part of a succesful bid for a GrantinAid for Scientific Research on Innovative Areas titled “Quantum Liquid Crystals” (KAKENHI Grant No. JP19H05825). And the former Unit member, Dr Olga Sikora, succesfully defended her Habilitation Thesis in Poland, based on work carried out in the TQM Unit.
The Unit published 10 papers in FY 2019, including one article in Proceedings of the National Academy of Science, three in Physical Review Letters (one of which was singled out as an Editor's suggestion and featured in Physics Magazine) and six in Physical Review B (one of which was also singled out as an Editor's suggestion). These covered a range of topics in the physics of quantum materials, and topological phases of matter.
Research highlights included the (probable) identification of quantum spin nematic phases in both volborthite and BaCdVO(PO4)2; the explanation of negative thermal expansion in CdCr2O4; the discovery of a "ripple" phase in honeycomb lattice antiferromagnets; further discoveries about the connections between fractons and holography; and the discovery of a route to fracton phases in real materials and an exploration of the properties of water ice in electric field. A significant new theme also emerged over the course of the year, namely use of Machine Learning as a tool for solving theoretical physics problems
The Unit remained active in promoting its work, giving a total of 30 presentations in FY2019, including 22 invited talks, among them seminars at MIT, Oxford, and Princeton. Many of the Unit also participated in the program "Topological Quantum Matter: Concepts and Realisations" at the Kavli Institute for Theoretical Physics (KITP,) in Santa Barbara, which was coorganised by Prof. Shannon. However two of the most significant conferences in which Unit members were due to participate, the APS March Meeting, and the JPS Spring Meeting, were cancelled as a result of the coronavirus.
The TQM Unit hosted a smaller number of visits and semianrs in FY 2019 than in previous years, both because of Prof. Shannon's sabbatical, and travel restrictions coming from the coronavirus. None the less 7 researchers did visit the Unit, giving 6 seminars. And at the end of FY2019, the TQM moved its seminar series online, by way of Zoom.
Outreach activity also took an interesting new turn: the TQM Unit was the subject of a film commissioned by the American Physical Society for its "APS TV", and a second film, profiling the Unit's former student Rico Pohle, was commissioned by OIST.
1. Staff
 Dr. Judit Romhanyi, Staff Scientist (~2019.08)
 Dr. Matthias Gohlke, Postdoctoral Scholar
 Dr. Geet Rakala, Postdoctoral Scholar
 Dr. Tokuro Shimokawa, Postdoctoral Scholar
 Ms. Leilee Chojnacki, PhD Student
 Mr. Soshi Mizutani, PhD Student
 Ms. Kimberly Remund, PhD Student
 Mr. Andreas Thomasen, PhD Student
 Mr. Han Yan, PhD Student
 Ms. Megumi Ikeda, Research Unit Administrator
2. Collaborations
2.1 Polarization plateaus in hexagonal water ice
 Type of collaboration: Joint research
 Researchers:
 Dr. Matthias Gohlke, OIST
 Prof. Roderich Moessner, MPIPKS Dresden, Germany
 Prof. Frank Pollmann, TU Munich, Garching, Germany
2.2 Fieldinduced pseudoGoldstone mode and nematic phase in the KitaevGamma model
 Type of collaboration: Joint research
 Researchers:
 Dr. Matthias Gohlke, OIST
 Mr. LI Ern Chern, University of Toronto, Canada
 Prof. Yong Baek Kim, University of Toronto, Canada
2.3 Machine learning the spinnon dynamics
 Desctiption: we explore how modern machine learning (ML) methods can be used to extend the time dependent dependent correctors which are obtained by tDMRG algorithm for quantum spin chain system with spinnon dynamics, and the performance is compared to the Bethe ansatz solution and the existing linear prediction method. For this project, ML and tDMRG calculations are carried out by Mizutani while Bethe ansatz calcuation is carried out by Caux, under the supervision of Shannon, Pollmann and Caux.
 Type of collaboration: Joint research
 Researchers:
 Mr. Soshi Mizutani, OIST
 Prof. Nic Shannon, OIST
 Prof. Frank Pollmann, Technical Univeristy of Munich
 Prof. JeanSébastien Caux, Institute of Physics, University of Amsterdam
2.4 Machine learning the quench dynamics
 Description: We apply machine learning based forecasting methods to extend the quenching signal of bose gas density function computed by DMFT and tDMRG and its long time behavior.
For this project, ML implementation is carried out by Mizutani while DMFT and tDMRG calcuations are carried out by Grundner, under the supervision of Shannon and Schollwöck.  Type of collaboration: Joint research
 Researchers:
 Mr. Soshi Mizutani, OIST
 Prof. Nic Shannon, OIST
 Mr. Martin Grundner, Ludwig Maximilian University of Munich
 Prof. Ulrich Schollwöck, Ludwig Maximilian University of Munich
2.5 Investigating Magnetic Phases of Matter Using Autoregressive Neural Networks
 Description: This collaboration investigates changes of state in condensed matter physics research by training a neural network to produce and sample probability distributions of spinconfigurations. The network is trained through free energy minimization using stateoftheart machine learning technology.
 Type of collaboration: Joint research
 Researchers:
 Prof. Judit Romhanyi, University of California Irvine
 Prof. Nic Shannon, OIST
 Mr. Andreas Thomasen, OIST
2.6 Chaotic FewBody Vortex Dynamics in Rotating BoseEinstein Condensates
 Description: Chaotic phenomena in physics are ubiquitous and numerous examples exist in the natural world as soon as one goes beyond the classical twobody problem. These are interesting because while the equations of motion are known, the solutions are generally not known analytically, and their evolution is hard to predict.In this study we tracked the trajectories of 4 vortices in a BoseEinstein condensate and identified chaotic behavior arising when one of the vortices had opposite winding as compared to the others. Chaotic behavior is generally observed most strongly when three or more vortices are in the vicinity of each other. These collisional events appear to be the main cause of chaotic behavior in Bose Einstein condensates we investigated.
 Type of collaboration: Joint research
 Researchers:
 Prof. Thomas Busch, OIST
 Dr. Angela White, OIST
 Dr. Lee O'Riordan, OIST
 Dr. James Schloss, OIST
 Mr. Tiantan Zhang, Norwegian University of Science and Technology
 Mr. Andreas Thomasen, OIST
2.7 Quantum dipolar spin ice in applied magnetic field
 Description: Quantum Monte Carlo simulations of a quantum dipolar spin ice in applied magnetic field.
 Type of collaboration: Joint research
 Researchers:
 Prof. Karlo Penc, Budapest
 Prof. Nic Shannon, OIST
 Prof. Frank Pollmann, TUM
 Dr. Olga Sikora, IFJ Krakow
2.8 Hard plates on a cubic lattice
 Type of collaboration: Joint research
 Researchers:
 Dr. Geet Rakala, OIST
 Prof. Kedar Damle, TIFR Mumbai, India
 Prof. Deepak Dhar, IISER, Pune, India
2.9 Triangular Ising antiferromagnet with further neighbour interactions
 Type of collaboration: Joint research
 Researchers:
 Dr. Geet Rakala, OIST
 Prof. Kedar Damle, TIFR Mumbai, India
2.10 Numerical simulation of spin1 magnets
 Type of collaboration: Joint research
 Researchers:
 Ms. Kimberly Remund, OIST
 Dr. Rico Pohle. Waseda University
 Prof. Judit Romhanyi, University of California Irvine
 Prof. Yutaka Akagi, The University of Tokyo
 Prof. Nic Shannon, OIST
2.11 Generalized hyperbolic fracton model
 Description: We study the generalized classical fracton topological order and subsystem symmetry protected states in the hyperbolic space. We will explore the subsystem symmetries of these models, the boundary state representations, and their relation to holographic entanglement entropy.
 Type of collaboration: Joint research
 Researchers:
 Mr. Han Yan, OIST
 Dr. Dominic Joseph Williamson, Stanford Universty
 Dr. ZhuXi Luo, KITP, University of California, Santa Barbara
2.12 Machine learning complex order
 Type of collaboration: Joint research
 Researchers:
 Mr. Han Yan, OIST
 Dr Ludovic Jaubert, Bordeaux
 Mr Nicolas Sadoune, LMU
 Dr Wan Ke, LMU
 Prof. Lode Pollet, LMU
 Prof. Nic Shannon, OIST
2.13 Topological bands in quantum magnets
 Type of collaboration: Joint research
 Researchers:
 Mr. Andreas Thomasen, OIST
 Mr Han Yan, OIST
 Prof. Judit Romhanyi, UCI
 Prof. Karlo Penc, Budapest
 Prof. Nic Shannon, OIST
2.14 Imaging magnetic monopoles in spin ice
 Type of collaboration: Joint research
 Researchers:
 Mr. Ankur Dahr, OIST
 Dr Ludovic Jaubert, CNRS Bordeaux
 Prof. Nic Shannon, OIST
 Prof. Tsumoru Shintake, OIST
3. Activities and Findings
1. Theory of exotic spin liquid sheds light on entanglement structure of quantum gravity.
The holographic principle has played a central role in the modern study of quantum gravity. It states that gravitational theory in a negatively curved spacetime is equivalent to a conformal quantum field theory on its boundary. Many toy models have been built to help us understand holography more intuitively, including the perfect tensornetworks, the bitthreads model, and more recently the fracton model proposed by the author.
In this work, the author proposed that all three types of toy models can be unified under the same picture: geodesic string condensation. Furthermore, a rank2 U(1) gauge theory, previously discussed in the constex of "fractons", and as a theory of exotic spin liquids, can also be considered as a linearized limit of gravity, and displays holographic properties when embedded in a curved spacetime. This work illuminates the how the holographic toy models are connected with gravity concretely.
This work is described in the preprint arXiv:1911.01007.
Machine learning has already revolutionised the way we think about tasks as complex as driving a car. But can machines also do science ? In this project, we revisit a challenging problem in condensedmatter physics, the determination of the phase diagram of frustrated magnet, originally studied by Taillefumier et al., [Phys. Rev. X 7 041057 (2017)] (cf. FY2016 Annual Report). The model in question is the XXZ model on a pyrochlore lattice, and the particular challenge lies in the fact that this supports three different types of spin liquid phases, as well as both conventional, and unconventional forms of magnetic order (cf. upper panel of Fig.).
The machine learning method used was a Support Vector Machine (SVM) with a tensorial kernel (TK) and graphical analysis, previously introduced by J. Greitemann et al. [Phys. Rev. B 99, 060404(R) (2019)]. This method of machine learning does not require the machine to be "trained" on established examples, and can be "interpreted", i.e. it is possible to interrogate the machine about how it reached its final decision. Starting from spin configurations taken from classical Monte Carlo simulation, the TKSVM correctly identified all of the phases found by Taillefumier et al. without any prior information about the type of phases present, completely reproducing the published phase diagram (cf. lower panel of Fig.1) . Moreover, the machine also correctly identified the organisational principle behind each phase, determining the correct order parameters for each of the ordered phases, and the correct local constraint for each of the spin liquids.
The striking success of the TKSVM in this case suggests that it will be possible to solve the phase diagrams of complex models without human input.
Fig.3(upper panel): Phase digram of the XXZ model on a pyrochlore lattice, as published by Taillefumier et al. [Phys. Rev. X 7, 041057 (2017)]. The phase digram is shown as a function of temperature and transverse exchange; three different forms of spin liquid compete with both magnetic and spinnematic order.
Fig.3(lower panel): Phase digram of the XXZ model on a pyrochlore lattice, as determined by machine learning, in the study by J. Greitemann et al. [Phys. Rev. B 100, 174408 (2019)]. The machine correctly identifies the same six phases as were found in the original study by Taillefumier et al., including three different types of spin liquids.
This work was a collaboration between members of the TQM Unit (OIST), members of the Theoretical Nanophysics Group (LMU Munich), and Dr Ludovic Jaubert of LOMA (CNRS Bordeaux). It was published as: "Identification of hidden order and emergent constraints in frustrated magnets using tensorial kernel methods", Jonas Greitemann, Ke Liu, Ludovic D.C. Jaubert, Han Yan, Nic Shannon, Lode Pollet, Phys. Rev. B 100, 174408 (2019)
4. Polarization Plateaus in Hexagonal Water Ice I_{h}
The most common form of Ice on earth can be considered as a paragon of geometric frustration. In the 1930s experiments revealed a discrepancy in the entropy between spectroscopic measurements and when integrating over the specific heat. This discrepancy stems from an extensive residual entropy caused by the ice rules: a single proton is placed on each of the four oxygenoxygen link per oxygen site. There are two protons bonded covalently to each oxygen ion forming H_{2}O molecules, while the two other protons form hydrogen bonds. As such the ice rules impose local constraints that prevent the H_{2}O molecules from ordering and leave an extensively degenerate proton subsystem with a finite residual entropy.
In this study, we have been considering a minimal model of hexagonal Ice I_{h} and how an external electric field affects the proton configuration. Depending on the direction the field is applied, the extensive degeneracy of the proton configurations is either fully or only partially lifted. The latter occurs if the field is applied along certain easy axis and a polarization plateau at intermediate polarization is observed. The remaining ground states within these intermediate polarization plateaus can be described in terms of dimer models on the honeycomb and the square lattice, respectively. Upon tilting the external field slightly away of these easy axis, we observe an orderdisorder transition of Kasteleyn type into a plateau at saturated polarization and vanishing entropy. In this work, the transition has been investigated analytically using the Kasteleyn matrix approach and numerically using a modified directedloop Monte Carlo simulation.
While the emergent dimers on a honeycomb lattice are known from pyrochlore spin ice in a magnetic field, the emergent dimers on a square lattice are due to the different lattice structure of Ice I_{h}. It remains an interesting question, whether the intermediate polarization plateaus can be observed experimentally in Ice I_{h}.
(a) Structure of Ice Ih and the two field directions considered.
(b) Upon applying the field along the [010] axis, a polarization plateau at intermediate polarization exists in which the remaining degrees of freedom (blue spins) map to dimers on a rhombic lattice.
This work was published in the article: "Polarization plateaus in hexagonal water ice I_{h}" Matthias Gohlke, Roderich Moessner, and Frank Pollmann, Phys. Rev. B 100, 014206 (2019)
5. Putative spinnematic phase in BaCdVO(PO_{4})_{2}
Like Volborthite, described below, BaCdVO(PO_{4})_{2} is a quasitwo dimensional magnet, with competing ferromagnetic and antiferromagnetic interactions. In such systems, it has been proposed that a new state of matter, known as a "spin nematic", can occur in high magnetic fields. BaCdVO(PO_{4})_{2} has previously been discussed as a candidate for spinnematic order [A. Smerald, H. T. Ueda, and N. Shannon, Phys. Rev. B 91, 174402 (2015)], but until now, relatively little has been known about the experimental phase diagram of this material.
In this paper, we identify for the first time the nature of the magnetic grounds state of BaCdVO(PO_{4})_{2} in the absence of magnetic field, and present evidence for the existence of a novel magnetic phase in applied magnetic field, consistent with predictions of spinnematic order. Evidence in support of this conclusion comes from elastic neutron scattering and dynamical susceptibility measurements on powder samples of BaCdVO(PO_{4})_{2}. These results, in combination with recent thermodynamics measurements on single crystals [K. Y. Povarov, V. K. Bhartiya, Z. Yan, and A. Zheludev, Phys. Rev. B 99, 024413 (2019)], establish BaCdVO(PO_{4})_{2}, like Volborthite, as a strong candidate for spinnematic order.
Fig.5 Magnetic phase diagram of BaCdVO(PO_{4})_{2}, as determined by measurements of magnetic susceptibility, showing how conventional magnetic order vanishes for fields approaching 4T, providing evidence for a new nonmagnetic phase where spinnematic order has been predicted.
This work was published in the article: "Putative spinnematic phase in BaCdVO(PO_{4})_{2}" M. Skoulatos, F. Rucker, G.J. Nilsen, A. Bertin, E. Pomjakushina, J. Ollivier, A. Schneidewind, R. Georgii, O. Zaharko, L. Keller, Ch. Rüegg, C. Pfleiderer, B. Schmidt, N. Shannon, A. Kriele, A. Senyshyn, and A. Smerald, Phys. Rev. B 100, 014405 (2019)
6. Chaotic fewbody vortex dynamics in rotating BoseEinstein condensates
Chaotic phenomena in physics are ubiquitous and numerous examples exist in the natural world as soon as one goes beyond the classical twobody problem. These are interesting because while the equations of motion are known, the solutions are generally not known analytically, and their evolution is hard to predict.
In this study we tracked the trajectories of 4 vortices in a BoseEinstein condensate and identified chaotic behavior arising when one of the vortices had opposite winding as compared to the others. Chaotic behavior is generally observed most strongly when three or more vortices are in the vicinity of each other. These collisional events appear to be the main cause of chaotic behavior in Bose Einstein condensates we investigated.
Fig.6 : The insets show the histograms of the COM trajectories calculated over 20 s of evolution for the system of four vortices when the position of a single vortex has been shifted by Δx=0ξ and Δx=ξ/3. The upper two panels depict the corresponding trajectories after the direction of rotation of a single vortex has been reversed, whereas the lower row displays the trajectories for the case where all vortices corotate. The main curve plots the corresponding Lyapunov exponents, calculated from the shown COM trajectories. The negative Lyapunov exponents (orange) indicate that shifting the vortex about the initial position still ensures the stability of vortex trajectories. Reversing the direction of circulation of a single vortex (blue) however leads to fluctuations about zero, eventually leading to a fully positive exponent.
This work was published in the article: "Chaotic fewbody vortex dynamics in rotating BoseEinstein condensates", Tiantian Zhang, James Schloss, Andreas Thomasen, Lee James O'Riordan, Thomas Busch, and Angela White, Phys. Rev. Fluids 4, 054701 (2019).
7. Possible observation of quantum spinnematic phase in the frustrated magnet volborthite
Every child learns that water freezes in the cold of winter, and evaporates quickly in the heat of summer. Scientifically, these transformations between solid, liquid and gas are called phase transitions, and the fact that the same atoms can exhibit different phases lies at the heart of our understanding of the material world. A fourth phase of matter was discovered, by chance, late in 19th century, when Freiedrich Reinitzer tried to make crystals from molecules of cholesterol. Reinitzer noticed that as he cooled his solution of cholesterol towards its freezing point, it underwent a marked change in its physical properties, while remaining a liquid. This was the first observation of a "liquid crystal", a phase of matter in which rod or diskshaped molecules align like the atoms in a solid, while continuing to flow like a liquid.
Liquid crystals have since become an important part of everyday life, and are integral to the displays in most electronic devices. Meanwhile, the search for new phase of matter, including quantum analogies of liquid crystals, has become an increasingly important field of research. One longsought example is the "quantum spin nematic", in which the quantum state of magnetic atoms mimic the rodlike molecules of a nematic liquid crystal. The possibility of this new phase of matter was first pointed half a century ago [M. Blume and Y. Y. Hsieh J Appl Phys 40, 1249 (1969); A. F. Andreev, I. A. Grishchuk, J Exp Theor Phys 97, 467 (1984)]. And it is now well understood how competing, or "frustrated", interactions between the ions in a magnet can give rise to a spinnematic phase [A. V. Chubukov, Phys. Rev. B 44, 4693 (1991); N. Shannon et al., Phys. Rev. Lett., 96, 027213 (2006)]. None the less, despite their considerable interest, quantum spin nematics have proved very difficult to observe in experiment.
In this work, we report the possible observation of a quantum spin nematic in the naturally occuring mineral, volborthite. Volborthite contains copper atoms which are magnetic, with interactions of type needed to promote a spinnematic state in high magnetic field [O. Janson et al., Phys. Rev. Lett. 117, 037206 (2016)]. We have probed the magnetic behaviour of the copper atoms by carrying out highprecision measurements of the way in which crystals of volborthite absorb heat, in fields of up to 33 Tesla. The results we find are consistent with the existence of a quantum spinnematic phase, at temperatures below 1.5 Kelvin, for magnetic fields ranging from 25.5 to 27.5 Tesla.
Fig.7 Magnetic phases found in volborthite in magnetic field of up to 33 Tesla, as determined by measurements of the magnetocaloric effect and specific heat. The phase marked "N_{2}", occurring for temperatures below 1.5 Kelvin, bears the hallmarks of a spin nematic phase.
This work was published in the article: "Possible observation of quantum spinnematic phase in a frustrated magnet", Yoshimitsu Kohama, Hajime Ishikawa, Akira Matsuo, Koichi Kindo, Nic Shannon, and Zenji Hiroi, Proc. Natl. Acad. Sci. 116, 10686 (2019).
4. Publications
4.1 Journals
 Han Yan, Owen Benton, Ludovic D.C. Jaubert and Nic Shannon, Rank2 U(1) spin liquid on the breathing pyrochlore lattice, doi: 10.1039/Phys. Rev. Lett. 124.127203 (2020)
 Han Yan, Hyperbolic Fracton Model, Subsystem Symmetry, and Holography II: The Dual EightVertex Model, doi: 10.1103/PhysRevB.100.245138 (2019)
 Tokuro Shimokawa, Tsuyoshi Okubo and Hikaru Kawamura, Multipleq states of the J_{1}J_{2} classical honeycomblattice Heisenberg antiferromagnet under magnetic fields, doi: 10.1103/PhysRevB.100.224404 (2019)
 Jonas Greitemann, Ke Liu, Ludovic D.C. Jaubert, Han Yan, Nic Shannon and Lode Pollet, Identification of emergent constraints and hidden order in frustrated magnets using tensorial kernel methods of machine learning, doi: 10.1103/PhysRevB.100.174408 (2019)
 Matthias Gohlke, Roderich Moessner, and Frank Pollmann, Polarization plateaus in hexagonal water ice I_{h}_{,}_{ }doi: 10.1103/PhysRevB.100.014206 (2019)
 M. Skoulatos, F. Rucker, G.J. Nilsen, A. Bertin, E. Pomjakushina, J. Ollivier, A. Schneidewind, R. Georgii, O. Zaharko, L. Keller, Ch. Rüegg, C. Pfleiderer, B. Schmidt, N. Shannon, A. Kriele, A. Senyshyn, and A. Smerald, Putative spinnematic phase in BaCdVO(PO_{4})_{2}, doi: 10.1103/PhysRevB.100.014405 (2019)
 Tokuro Shimokawa, and Hikaru Kawamura, Ripple state in the frustrated honeycomblattice antiferromagnet, doi: 10.1103/PhysRevLett.123.057202 (2019)
 L. Rossi, A. Bobel, S. Wiedmann, R. Küchler, Y. Motome, K. Penc, N. Shannon, H. Ueda, and B. Bryant, Negative thermal expansion in the plateau state of a magneticallyfrustrated spinel, doi: 10.1103/PhysRevLett.123.027205 (2019)
 Y. Kohama, H. Ishikawa, A. Matsuo, K. Kindo, N. Shannon and Z. Hiroi, Possible observation of quantum spin nematic phase in a frustrated magnet, doi: 10.1073/pnas.1821969116 (2019)
 Han Yan, Hyperbolic fracton model, subsystem symmetry, and holography, doi: 10.1103/PhysRevB.99.155126 (2019)
4.2 Books and other onetime publications
Nothing to report
4.3 Oral and Poster Presentations
Invited Talks at Conference
 Matthias Gohlke "Field Induced PseudoGoldstone Mode and Nematic States in Kitaev Magnets" 3rd AsiaPacific Workshop on Quantum Magnetism, Shanghai, China (2019.11.18)
 Han Yan "Fracton States of Matter as Toy Models of Holography" Youth Symposium on Theoretical High Energy Physics, Southeast University, China, (2019.08.21)
 Nic Shannon "Quantum Liquid Crystals in Magnets" Kickoff Meeting: Quantum Liquid Crystals, Tokyo, Japan (2019.08.19)
 Nic Shannon "From half moons to Chern numbers" TEMM and the joint TCMmagnetism IoP symposium, Abigdon, UK (2019.07.17)
 Judit Romhanyi "Topologically nontrivial excitations in quantum magnets" Competing Interactions and Colossal Responses in Transition Metal Compounds, Telluride Intermediate School, Colorado, USA (2019.06.27)
 Nic Shannon "An Introduction to Quantum Spin Liquids" 3rd TRR 80 Summer School" Functionality of Correlated Materials, Germany (2019.06.27)
Contributed Talks
 Tokuro Shimokawa "Finite and zero temperature physics in the S=1/2 bilayer breathingkagome magnet", 第１４回量子スピン系研究会, Akita, Japan (2020.01.08)
 Tokuro Shimokawa "Finitetemperature properties of the S=1/2 ShastrySutherland model" The Physical Society of Japan, Gifu, Japan (2019.09.13)
 Matthias Gohlke "Dynamical and Topological Properties of the Kitaev Model in a [111] Magnetic Field" 2019 Autumn Meeting, The Physical Society of Japan, Gifu, Japan (2019.09.13)
 Tokuro Shimokawa "Ripple state in the frustrated honeycomblattice antiferromagnet" Computational Approaches to Quantum Manybody Problems (CAQMP), ISSP, The University of Tokyo, Japan (2019.07.22)
 Nic Shannon "Designer spin liquids" DPG Fall Meeting, Regensburg 2019, Germany (2019.04.01)
Seminars
 Han Yan "Fracton States of Matter as Toy Models of Holography" Princeton Center for Theoretical Science, Princeton University, USA (2019.11.21)
 Han Yan "Rank–2 U(1) spin liquid on the breathing pyrochlore lattice" Condensed Matter Theory Seminar, MIT, USA (2019.11.12)
 Han Yan "Fracton States of Matter as Toy Models of Holography" Center for Theory of Quantum Matter, University of Colorado Boulder, USA (2019.10.25)
 Han Yan "Hyperbolic fracton model, subsystem symmetry, and holography" High Energy Accelerator Research Organization (KEK), Ibaraki, Japan (2019.09.19)
 Han Yan "Rank2 U(1) spin liquid on the breathing pyrochlore latticeRank2 U(1) spin liquid on the breathing pyrochlore lattice" Condensed Matter Theory Group, Paul Scherrer Institute, Switzerland (2019.08.06)
 Han Yan "Fracton Model and Holography" Condensed Matter Theory Group Technical University of Munich, Germany, (2019.08.01)
 Han Yan "Fracton Model and Holography" LOMA, University of Bordeaux, France (2019.07.23)
 Tokuro Shimokawa "Ripple state in the frustrated honeycomblattice Heisenberg antiferromagnet" Tokyo University of Science, Tokyo, Japan (2019.07.19)
 Tokuro Shimokawa "Ripple state in the frustrated honeycomblattice Heisenberg antiferromagnet" Technical University of Munich, Munich, Germany (2019.06.06)
 Tokuro Shimokawa "Ripple state in the frustrated honeycomblattice Heisenberg antiferromagnet" HelmholtzZentrum DresdenRossendorf, Dresden, Germany (2019.06.04)
 Judit Romhanyi "Hall responses in larger spin quantum magnets" RIKEN, Saitama, Japan (2019.06.03)
 Nic Shannon "Designer spin liquids" Laboratoire de Physique Théorique, Toulouse, France (2019.05.23)
 Nic Shannon "A Hitchiker's Guide to Frustrated Magnets" LOMA of the University of Bordeaux, France (2019.05.21)
 Nic Shannon "Designer spin liquids" MPI for Solid State Research, Germany (2019.05.16)
 Tokuro Shimokawa "Ripple state in the frustrated honeycomblattice Heisenberg antiferromagnet" RIKEN, Japan (2019.05.15)
 Nic Shannon "An Introduction to Quantum Spin Nematics" ETH Zürich, Hönggerberg, Switzerland (2019.05.09)
 Nic Shannon "Designer spin liquids" University of Oxford, UK (2019.04.16)
Poster Presentations
 Nic Shannon "Theory of Quantum Matter Unit" OISTHitachi joint symposium, Hitachi R&D, Japan (2020.02.17)
 Tokuro Shimokawa "Ground state and thermodynamic properties of the S=1/2 bilayer breathingkagome Heisenberg magnet" Computational Approaches to Quantum Manybody Problems (CAQMP) 2019 , Kashiwa, Japan (2019.08.05)
 Geet Rakala "Hard plates on a cubic lattice" Statphys 27, Buenos Aires, Argentina (2019.07.10)
 Han Yan "Fracton Model and Holography" YITP, Kyoto University, Japan (2019.06.12)
5. Intellectual Property Rights and Other Specific Achievements

APS TV Film : Film about the TQM Unit commisioned for APS TV, and made to be shown at the 2020 March Meeting of the American Physical Society.
6. Meetings and Events
Seminar
6.1 Hopfions in 3D dimer models
 Date: March 26, 2020
 Venue: Zoom Seminar
 Speaker: Dr. Grigory Bednik (University of California Santa Cruz, USA)
6.2 Firstprinciples study for material science
 Date: March 10, 2020
 Venue: OIST Campus Lab3
 Speaker: Associate Prof. Yasutomi Tatetsu (University Center for Liberal Arts Education, Meio University, Japan)
6.3 Quantum spin liquid candidate Ca10Cr7O28 – A spinon description
 Date: February 18, 2020
 Venue: OIST Campus Lab3
 Speaker: Mr. Jonas Sonnenschein (Freie University of Berlin, Germany)
6.4 Magnetic Field Induced Competing Phases in Kitaev Magnets
 Date: January 22, 2020
 Venue: OIST Campus Lab1
 Speaker: Dr. Ryui Kaneko (Institute for Solid State Physics, University of Tokyo, Japan)
6.5 Numerical simulations of spin1 magnets
 Date: April 25, 2019
 Venue: OIST Campus Lab1
 Speaker: Dr. Rico Pohle (Waseda University, Japan)
6.6 Finitetemperature spectra of spinorbit coupled Mott insulators
 Date: April 24, 2019
 Venue: OIST Campus Lab1
 Speaker: Prof. Youhei Yamaji (Department of Applied Physics, the University of Tokyo, Japan)
6.7 Representation of Quantum Manybody System by Neural Networks
 Date: April 17, 2019
 Venue: OIST Campus Lab2
 Speaker: Mr. Nobuyuki Yoshioka (University of Tokyo, Katsura group, Japan)
7. Other
Nothing to report.