BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CMSA - ECPv6.17.1//NONSGML v1.0//EN CALSCALE:GREGORIAN METHOD:PUBLISH X-WR-CALNAME:CMSA X-ORIGINAL-URL:https://cmsa.fas.harvard.edu X-WR-CALDESC:Events for CMSA REFRESH-INTERVAL;VALUE=DURATION:PT1H X-Robots-Tag:noindex X-PUBLISHED-TTL:PT1H BEGIN:VTIMEZONE TZID:America/New_York BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20220313T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20221106T060000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20230312T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20231105T060000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20240310T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20241103T060000 END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTART;TZID=America/New_York:20231004T103000 DTEND;TZID=America/New_York:20231004T113000 DTSTAMP:20240221T111849Z CREATED:20240221T111722Z LAST-MODIFIED:20240221T111849Z UID:10002779-1696415400-1696419000@cmsa.fas.harvard.edu SUMMARY:Dipolar and modulated symmetry protected topological phases DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Ho Tat Lam\, MIT \nTitle: Dipolar and modulated symmetry protected topological phases \nAbstract: Modulated symmetries are symmetries whose symmetry generators exhibit spatial modulations. We will discuss one-dimensional symmetry protected topological (SPT) phases protected by modulated symmetries. We will present a simple recipe for constructing modulated SPT models by generalizing the concept of decorated domain walls. We will then focus on the simplest modulated SPT protected by dipolar symmetries\, classify them using matrix product states and construct their response field theories using twisted finite tensor gauge theories. URL:https://cmsa.fas.harvard.edu/event/tqms_10423/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-10.04.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231016T140000 DTEND;TZID=America/New_York:20231016T150000 DTSTAMP:20240222T090812Z CREATED:20240222T090812Z LAST-MODIFIED:20240222T090812Z UID:10002793-1697464800-1697468400@cmsa.fas.harvard.edu SUMMARY:Breaking ergodicity: quantum scars and regular eigenstates DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Ceren Dag\, Harvard \nTitle: Breaking ergodicity: quantum scars and regular eigenstates \nAbstract: Quantum many-body scars (QMBS) consist of a few low-entropy eigenstates in an otherwise chaotic many-body spectrum and can weakly break ergodicity resulting in robust oscillatory dynamics. The notion of QMBS follows the original single-particle scars introduced within the context of quantum billiards\, where scarring manifests in the form of a quantum eigenstate concentrating around an underlying classical unstable periodic orbit (UPO). A direct connection between these notions remains an outstanding problem. Here\, we study a many-body spinor condensate that\, owing to its collective interactions\, is amenable to the diagnostics of scars. We characterize the system’s rich dynamics\, spectrum\, and phase space\, consisting of both regular and chaotic states. The former are low in entropy\, violate the Eigenstate Thermalization Hypothesis (ETH)\, and can be traced back to integrable effective Hamiltonians\, whereas most of the latter are scarred by the underlying semiclassical UPOs\, while satisfying ETH. We outline an experimental proposal to probe our theory in trapped spin-1 Bose-Einstein condensates. If time permits\, I will also mention our latest efforts in introducing spatial dimension to this model with a true semiclassical limit\, and how quantum scars persist to exist in a many-body system. Reference: arXiv 2306.10411\, in peer review. URL:https://cmsa.fas.harvard.edu/event/tqms_101623/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-10.16.23.docx-1.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231018T123000 DTEND;TZID=America/New_York:20231018T133000 DTSTAMP:20240223T113334Z CREATED:20240223T113304Z LAST-MODIFIED:20240223T113334Z UID:10002866-1697632200-1697635800@cmsa.fas.harvard.edu SUMMARY:Composite fermions and the fractional quantum anomalous Hall effect DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Hart Goldman\, University of Chicago \nTitle: Composite fermions and the fractional quantum anomalous Hall effect \nAbstract: Recent experiments have revealed evidence for fractional quantum anomalous Hall (FQAH) states at zero magnetic field in a growing number of moire materials. In this talk\, I will argue that a composite fermion description\, already a unifying framework for the phenomenology of 2d electron gases at high magnetic fields\, provides a similarly powerful perspective in this new zero-field context. In particular\, a central prediction of the composite fermion framework is a non-Fermi liquid metal of composite fermions at even-denominator fillings. To this end\, I will present exact diagonalization evidence for such composite Fermi liquid states at zero magnetic field in twisted MoTe2 bilayers\, at fillings n = 1/2 and n = 3/4. Dubbing these states anomalous composite Fermi liquids (ACFLs)\, I will argue that they play a central organizing role in the FQAH phase diagram. I will also develop a long wavelength theory for this ACFL state\, which offers concrete experimental predictions that I will discuss in relation to current measurements. For example\, upon doping the composite Fermi sea\, one obtains a Jain sequence of FQAH states consistent with those observed experimentally\, as well as a new type of commensurability oscillations originating from the superlattice potential intrinsic to the system. Finally\, I will discuss opportunities for new physics not possible in quantum Hall systems at finite magnetic field. URL:https://cmsa.fas.harvard.edu/event/tqms_101823/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-10.18.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231101T103000 DTEND;TZID=America/New_York:20231101T113000 DTSTAMP:20240222T111747Z CREATED:20240222T111415Z LAST-MODIFIED:20240222T111747Z UID:10002806-1698834600-1698838200@cmsa.fas.harvard.edu SUMMARY:Unveiling Correlated Topological Insulators through Fermionic Tensor Network States DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Shenghan Jiang\, Kavli Institute for Theoretical Sciences UCAS \nTitle: Unveiling Correlated Topological Insulators through Fermionic Tensor Network States \nAbstract: The study of topological band insulators has revealed fascinating phases characterized by band topology indices\, harboring extraordinary boundary modes protected by anomalous symmetry actions. In strongly correlated systems\, it has been established that topological insulator phases persist as stable phases. However\, due to the inability to express the ground states of such systems as Slater determinants\, the formulation of generic variational wavefunctions for numerical simulations is highly desirable.\nIn this talk\, we tackle this challenge by developing a comprehensive framework with fermionic tensor network states. Starting from simple assumptions\, we write down tensor equations\, construct edge theories and extract quantum anomaly data for topological insulators. By exhaustively exploring all possible sets of equations\, we achieve a systematic classification of topological insulator phases. Imposing the solutions of a given set of equations onto local tensors\, we obtain generic variational wavefunctions for corresponding topological insulator phases. Our methodology provides a crucial first step towards simulating topological insulators in strongly correlated systems. \n  URL:https://cmsa.fas.harvard.edu/event/tqms_11123/ LOCATION:Virtual CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-11.01.23.docx-1.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231102T163000 DTEND;TZID=America/New_York:20231102T180000 DTSTAMP:20240222T112133Z CREATED:20240222T112133Z LAST-MODIFIED:20240222T112133Z UID:10002808-1698942600-1698948000@cmsa.fas.harvard.edu SUMMARY:Landscape of quantum phases in quantum materials DESCRIPTION:Joint Quantum Matter in Mathematics and Physics and Topological Quantum Matter Seminar \nSpeaker: Liujun Zou (Perimeter Institute) \nTitle: Landscape of quantum phases in quantum materials\n\nAbstract: A central goal of condensed matter physics is to understand which quantum phases of matter can emerge in a quantum material. For this purpose\, one should be able to not only describe the quantum phases using some effective field theories\, but also capture the important microscopic information of the material via mathematical formulation. In this talk\, I will present a framework to classify quantum phases in quantum materials\, where the microscopic information of a material is encoded in its quantum anomaly. I will talk about the application of this framework to classify various exotic quantum phases of matter in different lattice systems. Using our framework\, we have obtained many results unexpected from the previous literature. URL:https://cmsa.fas.harvard.edu/event/tqms_102523/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Quantum Matter,Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Special-Joint-QMMP-Topological-QM-11.02.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231109T163000 DTEND;TZID=America/New_York:20231109T173000 DTSTAMP:20240222T110327Z CREATED:20240222T110254Z LAST-MODIFIED:20240222T110327Z UID:10002805-1699547400-1699551000@cmsa.fas.harvard.edu SUMMARY:Uniqueness of Landau levels and their analogs with higher Chern numbers DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Bruno Mera\, Instituto Superior Tecnico \nTitle: Uniqueness of Landau levels and their analogs with higher Chern numbers \nAbstract: Lowest Landau level wavefunctions are eigenstates of the Hamiltonian of a charged par- ticle in two dimensions under a uniform magnetic field. They are known to be holomorphic both in real and momentum spaces\, and also exhibit uniform\, translationally invariant\, geometrical properties in momentum space. In this talk\, using the Stone-von Neumann the- orem\, we show that lowest Landau level wavefunctions are indeed the only possible states with unit Chern number satisfying these conditions. We also prove the uniqueness of their direct analogs with higher Chern numbers and provide their expressions. \nRef: Bruno Mera and Tomoki Ozawa. Uniqueness of Landau levels and their analogs with higher Chern numbers. arXiv:2304.00866\, 2023. arXiv:2304.00866. \n  URL:https://cmsa.fas.harvard.edu/event/tqms_11823/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-11.09.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231115T103000 DTEND;TZID=America/New_York:20231115T113000 DTSTAMP:20240222T105913Z CREATED:20240222T105852Z LAST-MODIFIED:20240222T105913Z UID:10002803-1700044200-1700047800@cmsa.fas.harvard.edu SUMMARY:A bulk gap in the presence of edge states for a truncated Haldane pseudopotential DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Amanda Young\, UIUC \nTitle: A bulk gap in the presence of edge states for a truncated Haldane pseudopotential \nAbstract: Haldane pseudopotentials were first introduced as Hamiltonian models for the fractional quantum Hall effect\, and it has been long expected that they should exhibit the characteristic properties of this exotic phase of matter\, including a spectral gap above the ground state energy. We will discuss recent work that verified this gap conjecture for a truncated version of the 1/3-filled Haldane pseudopotential in the cylinder geometry. Numerical evidence suggested that for open boundary conditions the gap of the truncated model closes as the cylinder radius converges to zero and that this closure is due to the presence of edge modes; in contrast\, for periodic boundary conditions\, the gap remains robustly order one in the same radius limit. The standard scheme for applying spectral gap estimating techniques to the model with periodic boundary conditions\, though\, produces a lower bound on the bulk gap that still reflects the energy of the edge modes. To obtain an estimate on the bulk gap that reflects its true behavior\, a new gap estimating strategy was developed. By customizing the spectral gap method to key invariant subspaces of the Hamiltonian\, we are able to successfully avoid the edge states and produce a more accurate lower bound on the bulk gap. In this talk\, we discuss this invariant subspace strategy for proving bulk gaps in the presence of edge states. This is based off joint work with S. Warzel. \n  \n  URL:https://cmsa.fas.harvard.edu/event/tqms_111523/ LOCATION:Virtual CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-11.15.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231120T140000 DTEND;TZID=America/New_York:20231120T150000 DTSTAMP:20240222T105558Z CREATED:20240222T103744Z LAST-MODIFIED:20240222T105558Z UID:10002800-1700488800-1700492400@cmsa.fas.harvard.edu SUMMARY:Emergent composite-fermion Luttinger liquid at the half-filled Landau level DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Prashant Kumar\, University of Chicago \nTitle: Emergent composite-fermion Luttinger liquid at the half-filled Landau level \nAbstract: The half-filled Landau level is a fascinating point in the phase diagram of quantum Hall effect that has been hypothesized to be a non-Fermi liquid where composite-fermions (CFs) emerge at low energies. In this talk\, I will present our numerical calculations of the excitation spectrum of this state on infinite cylinders. By comparing our results with a quasi-1D theory of CFs\, we show compelling quantitative evidence for the emergence of a Luttinger liquid of composite-fermions at low energies\, distinct from that of electrons. I will comment on some future directions. URL:https://cmsa.fas.harvard.edu/event/tqms_112023/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-11.20.23-1.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231129T170000 DTEND;TZID=America/New_York:20231129T180000 DTSTAMP:20240221T100813Z CREATED:20240221T100735Z LAST-MODIFIED:20240221T100813Z UID:10002773-1701277200-1701280800@cmsa.fas.harvard.edu SUMMARY:Anomalous Landau level analog in solids: search and implications for 2d heterostructures DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Valentin Crepel\, Flatiron Institute \nTitle: Anomalous Landau level analog in solids: search and implications for 2d heterostructures \nAbstract: The recent experimental observation of fractional Chen insulators — the analog of fractional quantum Hall states realized in absence of any applied magnetic field — calls for more detailed theoretical investigations of the special conditions allowing their emergence. To gain some insight on this problem\, we can rely on (i) our extensive knowledge of the physical properties of Landau levels\, and (ii) the identification of their exact solid state analogs. \nIn this talk\, (i-ii) will be discussed in the case of ”anomalous Landau levels”\, which are protected by an index theorem\, and whose most famous representative are the zero-th Landau levels of graphene. In particular\, I will derive the generic form of Bloch wave functions realizing the analog of such anomalous Landau levels\, and argue that twisted transition metal dichalcogenides homobilayers (in which fractional Chern insulators were first discovered) almost realize such anomalous bands. URL:https://cmsa.fas.harvard.edu/event/tqms_112923/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-11.29.23.docx-1_Page_1.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231201T163000 DTEND;TZID=America/New_York:20231201T173000 DTSTAMP:20240222T103010Z CREATED:20240222T101228Z LAST-MODIFIED:20240222T103010Z UID:10002799-1701448200-1701451800@cmsa.fas.harvard.edu SUMMARY:Quantum information: the interplay of mathematics and physics DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Kaifeng Bu (Harvard University) \nTitle: Quantum information: the interplay of mathematics and physics \nAbstract: I will provide an introduction to quantum information\, which points to a new connection with experiment on the one hand\, and a potential new area of mathematical analysis on the other. I will introduce two recent results about the application of this new area in quantum information: (1) a novel Quantum Central Limit Theorem (QCLT)\, and (2) a physically realizable protocol for testing and measuring quantum advantage. This talk is based on a collaboration with Arthur Jaffe\, and Weichen Gu (PNAS120(25)2023\, arXiv: 2302.08423\, arXiv:2306.09292). \n  URL:https://cmsa.fas.harvard.edu/event/tqms_12123/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-12.01.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231204T140000 DTEND;TZID=America/New_York:20231204T150000 DTSTAMP:20240226T112046Z CREATED:20240226T112024Z LAST-MODIFIED:20240226T112046Z UID:10002869-1701698400-1701702000@cmsa.fas.harvard.edu SUMMARY:The Fractional Quantum Hall Effect at ν=5/2: Past\, Recent\, and Future DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker:  Ken K. W. Ma (Northeastern University) \nTitle: The Fractional Quantum Hall Effect at ν=5/2: Past\, Recent\, and Future \nAbstract: The discovery of fractional quantum Hall (FQH) states started a new chapter in modern physics. Nowadays\, more than 70 FQH states at different filling factors have been observed. Among them\, the FQH state at the filling factor ν=5/2 in GaAs (or the 5/2 state) remains one of the most special and attractive states. Since its discovery in 1987\, different possible topological orders have been proposed to describe the 5/2 state. Some of them can host an exotic type of particles\, known as non-Abelian anyons. Recent experiments have provided more insights into the understanding of the 5/2 state\, but its underlying nature is still under debate. \nIn this talk\, I will review the basics of the 5/2 state [1] and a more unified theoretical description of different possible topological orders of the 5/2 state that we have recently proposed [2]. I will also review the groundbreaking thermal Hall conductance experiment [3] and the follow-up quantum Hall interface experiments by the Weizmann Institute group [4\, 5]\, and discuss what possible lessons that we can learn from the experimental results. Lastly\, I will talk about some possible directions and related topics for future investigations. \nReferences: \n[1] K. K. W. Ma\, M. R. Peterson\, V. W. Scarola\, and K. Yang\, “Fractional quantum Hall effect at the filling factor ν = 5/2” in Encyclopedia of Condensed Matter Physics (Second Edition)\, edited by T. Chakraborty\, Academic Press (2024).\n[2] K. K. W. Ma and D. E. Feldman\, “The sixteenfold way and the quantum Hall effect at half-integer filling factors”\, Phys. Rev. B 100\, 035302 (2019).\n[3] M. Banerjee\, M. Heiblum\, V. Umansky\, D. E. Feldman\, Y. Oreg\, and A. Stern\, “Observation of half-integer thermal Hall conductance”\, Nature (London) 559\, 205 (2018).\n[4] B. Dutta\, W. Yang\, R. Melcer\, H. K. Kundu\, M. Heiblum\, V. Umansky\, Y. Oreg\, A. Stern\, D. Mross\, “Distinguishing between non-Abelian topological orders in a quantum Hall system”\, Science 375\, 193 (2021).\n[5] B. Dutta\, V. Umansky\, M. Banerjee\, and M. Heiblum\, “Isolated ballistic non-Abelian interface channel”\, Science 377\, 1198 (2022). \n  URL:https://cmsa.fas.harvard.edu/event/tqms_12423/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Topological Quantum Matter Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-12.04.23.png END:VEVENT END:VCALENDAR