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: 9am, March 13 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Ruochen Ma
Title: Circuit-based characterization of finite-temperature quantum phases and self-correcting quantum memory
Abstract: Quantum phases at zero temperature can be defined as equivalence classes under local unitary transformations: two ground states are in the same phase if they can be transformed into each other via a local unitary circuit. In this talk, I will discuss how to generalize this circuit-based characterization of phases to systems at finite-temperature described by Gibbs states. We construct a local quantum channel circuit that approximately transforms one Gibbs state into another provided the two are connected by a path in parameter space along which a certain correlation-decay condition holds. This correlation-decay condition is expected to be satisfied in the interior of many noncritical thermal phases. As an application, I will show that any system in the same thermal phase as a zero-temperature topological code coherently preserves quantum information for a macroscopically long time, establishing self-correction as a universal property of thermal phases.
Time: 9am, March 20 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Shao-Kai Jian
Title: Quantum charge-4e superconductivity and deconfined (pseudo-)criticality in the attractive SU(4) Hubbard model
Abstract: Unlike conventional charge-2e superconductors, a charge-4e superconductor exhibits long-range coherence of electron quartets rather than Cooper pairs. Yet clear examples of zero-temperature quantum charge-4e superconductivity remain rare. Here, we investigate the zero-temperature phase diagram of the attractive SU(4) Hubbard model using sign-problem-free determinant quantum Monte Carlo simulations and identify both charge-2e and charge-4e superconducting phases. Across the charge-2e–charge-4e transition, single electrons remain gapped, while the observed scaling behavior is inconsistent with a conventional Landau description. These features are naturally captured by a fractionalized framework in which the physical charge-2e order parameter is a composite field coupled to an emergent non-Abelian gauge structure. We formulate an Sp(4) gauge-Higgs theory that realizes deconfined quantum (pseudo-)criticality between the Higgs (charge-2e) phase and the confined (charge-4e) phase. Remarkably, the one-loop critical exponents of the Sp(4) gauge-Higgs theory are in good agreement with our numerical results. We also discuss the fate of the physical electron across the transition.
Time: 9am, March 27 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Pengfei Zhang
Title: TBD
Abstract: TBD
There is no seminar during the week of March 30 2026 because of the Good Friday.
Time: 9am, April 10 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Sahand Seifnashri
Title: TBD
Abstract: TBD
Time: 9am, April 17 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Samuel Garratt
Title: TBD
Abstract: TBD
The seminar series in the spring semester of 2026 is over, and the next seminar will take place in the fall semester of 2026.