Department of Physics, National University of Singapore
Condensed Matter Seminar Series
To receive email notifications of this seminar series, please send an email to zouliujun@gmail.com to request.
Condensed Matter Seminar Series
To receive email notifications of this seminar series, please send an email to zouliujun@gmail.com to request.
Upcoming Seminars
(Both online and in-person seminars will be broadcast via Zoom.)
(Click the upper right corner of this page to see the previous seminars and their recordings.)
Time: 11 am, September 3 2026, GMT+8
Location: S11-02-07 at NUS
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Zhicheng Yang
Title: State k-designs from Hamiltonian evolution
Abstract: We study the generation of state ๐-designs from time evolution under a fixed Hamiltonian. Specifically, we consider the ensemble โฐ = {๐โปโฑแดดแต|๐โโฉ | ๐ก โผ Unif[0, ๐], |๐โโฉ โผ โฐโฒ}, where the initial states are sampled from an ensemble โฐโฒ. For Hamiltonians drawn from the Gaussian unitary ensemble, we derive a simple relation between the frame potential of the evolved ensemble โฐ and that of the initial ensemble โฐโฒ in the large evolution time limit. This relation shows that โฐ forms an exact state ๐-design in the thermodynamic limit as long as โฐโฒ forms a state 1-design. Remarkably, we further show, both analytically and numerically, that time evolution under a simple nonintegrable mixed-field Ising Hamiltonian can generate approximate state ๐-designs with high precision, starting from product states in an appropriately chosen Pauli basis. We also analyze the finite-๐ correction and find that it scales as ๐(1/๐). To reduce the evolution time, we propose an ๐-step quench protocol that suppresses this correction to ๐(1/๐แดน), which is also verified numerically. We then extend our analysis to unitary ensembles, deriving an analogous recursion relation for the unitary frame potential. Our results elucidate the mechanisms underlying recent proposals for generating unitary ๐-designs through sequential quantum quenches in a unified manner.
Time: 9am, September 11 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Zhengyan Darius Shi
Title: New physics in composite Fermi liquids from symmetry reduction
Abstract: The concept of composite fermions (CF) is a cornerstone of the quantum Hall phase diagram. Famously, in the half-filled Landau level, CFs form an itinerant metallic state known as the composite Fermi liquid (CFL), which is arguably the best understood example of a non-Fermi liquid metal without well-defined quasiparticles. In the conventional Landau level setting, Galilean symmetry forces the CF dispersion to be circularly symmetric in momentum space. While this symmetry simplifies many calculations, it conceals some of the most striking phenomena intrinsic to CFs. In this talk, I will explain how these phenomena emerge when the symmetries of the CFL state are reduced. Motivated by the recent experimental realization of a zero-field CFL in twisted MoTe2 and rhombohedral graphene, we consider a CF bandstructure with three-fold rotation symmetry and no inversion symmetry. We show that: (1) in the CFL state, broken inversion leads to a quantum critical optical conductivity that probes the dynamical exponent of the gauge fluctuations; broken continuum translation leads to a power-law temperature-dependent resistivity.ย (2) pairing of CFs with broken inversion gives a novel composite Bogoliubov Fermi liquid (CBFL) with a gapless Bogoliubov Fermi surface of CFs. Among its many exotic properties, the CBFL realizes a stable gapless topological phase with a two-fold torus ground state degeneracy, which does not fit into the "fractionalized Fermi liquid" framework. These results promise new physics of CFs in various FQAH platforms that extend beyond the half-filled Landau level.ย
Time: 9am, September 18 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Guo-Yi Zhu
Title: TBD
Abstract: TBD
Time: 9am, October 2 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Lei Gioia
Title: TBD
Abstract: TBD
Time: 9am, October 16 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Rahul Sahay
Title: TBD
Abstract: TBD
Time: 9am, October 23 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Ruizhi Liu
Title: TBD
Abstract: TBD
Time: 9am, October 30 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Jacob Zavatone-Veth
Title: TBD
Abstract: TBD
Time: 9am, November 6 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Gautam Greddy
Title: TBD
Abstract: TBD
Time: 9am, November 13 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/88911975409?pwd=ixb7zXPuROkgclFcXZ2Wzh5vx6fmz4.1
Password: 835700
Speaker: Linhao Li
Title: TBD
Abstract: TBD
The seminar series in the fall semester of 2026 is over, and the next seminar will take place in the spring semester of 2027.