Colloquium

Zoom Link: https://oklahoma.zoom.us/j/4881880273

Host: Arne Schwettmann

Title: "Engineering coherent quantum systems in atomic qubit platforms"

Abstract: Advances in quantum computation and simulation rely critically on the ability to precisely control complex, interacting atomic systems while maintaining long coherence times. In this talk, I will present my work on engineering high-fidelity quantum control across two leading atomic platforms — trapped ions and neutral atom arrays — highlighting approaches to controlling internal and motional degrees of freedom under realistic experimental constraints.

I will first describe techniques developed during my PhD work in trapped-ion systems for robust multi-qubit operations, including control of collective motional modes, pulse-design strategies that mitigate sensitivity to experimental imperfections, and quantum simulation using motional modes of a long ion chain. I will then discuss my postdoctoral work on neutral ytterbium atom arrays, where long-lived atomic states and flexible optical control enable new opportunities for scalable quantum computation and simulation. I will present recent experimental advances in coherent control, non-destructive readout, and atom–photon interfaces. Together, these results illustrate a platform-spanning approach to precision quantum control and motivate future directions toward scalable atomic quantum systems that integrate computation, simulation, and modular architectures.

Host: Kieran Mullen

Title: "Molecular Design Principles for Organic and Hybrid Materials: Insights into Topological States and Beyond"

Abstract: Organic frameworks (COFs & MOFs) have emerged as versatile platforms for exploring new electronic and quantum phenomena. Their modular “bottom-up” design, structural tunability, and chemical diversity make them ideal candidates for realizing tailored electronic structures and even unconventional topological states. Clear and predictive rules that connect molecular building blocks to emergent electronic behavior in extended lattices remain a central challenge. In this talk, I will discuss our efforts to build such connections and to adopt them for the rational design of quantum functionalities in organic materials. I will begin by introducing an effective theoretical framework that enables controlled band engineering in polymer networks. It reveals the fundamental relationships among lattice symmetries, frontier molecular orbitals, and the resulting electronic properties of COFs [1]. Building on this foundation, I will then present our discovery of a topological Dirac semimetal phase in a phthalocyanine-based COF composed solely of light elements, where external strain drives a transition from a trivial insulator to a topological semimetal [2]. I will then focus on heterotriangulene-based COFs and show how variations in the core heteroatoms and linker chemistry can promote higher-order topological insulating state [3]. Additionally, I will briefly overview other studies that broaden the scope of my research. These include investigations of the structure-property relationships in the highly conductive n-type polymer, poly(benzodifurandione) [4,5], as well as uncovering how organic cation engineering and quantum confinement govern the properties of low-dimensional hybrid perovskites [6,7]. These efforts demonstrate a unified molecular-level strategy for designing organic and hybrid materials with tailored properties and quantum states, offering fundamental insight into the molecular-to-materials relationships.

References:
1. Ni, X.; Li, H.; Liu, F.; Bredas, J.L. Mater. Horiz. 2022, 9, 88–98.
2. Ni, X.; Huang, H.; Bredas, J.L. Chem. Mater. 2022, 34, 3178–3184.
3. Ni, X.; Huang, H.; Bredas, J.L. J. Am. Chem. Soc. 2022, 144, 22778–22786.
4. Ni, X.; Li, H., Bredas, J.L. Chem. Mater. 2023, 35, 5886–5894.
5. Ni, X., Li, H., Coropceanu, S., Bredas, J.L. ACS Mater Lett 2024, 6, 2569.
6. Ni, X.; Li, H.; Bredas, J.L. ACS Mater Lett 2024, 6, 3436.
7. Zhong, X.†; Ni, X.†; Sidhik, S.; Li, H.; Mohite, A.D.; Bredas, J.L; Kahn, A. Adv. Energy Mater. 2022, 12, 2202333. (†Equal contribution)

Host: Kieran Mullen

Title: "Beyond Twistronics: Flat Bands Without Magic"

Abstract: Flat electronic bands have emerged as a powerful route to correlated and topological quantum matter, but in moiré systems they rely on extreme geometric fine tuning. I present an alternative paradigm in which externally imposed superlattice potentials generate flat bands in a deterministic and broadly tunable way, without requiring magic angles. Using graphene multilayers as a representative platform, I show that superlattice modulation produces both topological flat bands and stacked flat bands with favorable quantum geometry over extended parameter regimes. Band flatness, topology, and geometry can be controlled via superlattice symmetry, period, and displacement fields, offering direct access to conditions relevant for fractional Chern insulators and other correlated phases. This establishes superlattice engineering as a general and experimentally realistic platform for designing flat-band quantum matter beyond twistronics.

Host: Kieran Mullen

Title: "Square-planar nickelates: where nickelate superconductivity began"

Abstract: Superconductivity is one of the most fascinating phases of matter, with fundamental significance and transformative technological potential. However, superconductivity at ambient pressure typically occurs at temperatures far too low for widespread applications. As a result, the design, prediction, and discovery of new superconducting materials with higher critical temperatures remain central challenges in condensed matter physics. In this colloquium, I will review the landscape of high-temperature (high-Tc) superconductivity in the cuprate materials and discuss recent breakthroughs in square-planar superconducting nickelates. Using ab initio electronic structure methods combined with many-body approaches, I will show how these nickelates can be understood as close analogs of the cuprates, while also highlighting key distinctions that make them a new platform for exploration. I will conclude by offering a perspective on the future directions and open questions in the nascent field of nickelate superconductivity.

Host: Arne Schwettmann

Host: Arne Schwettmann

Host: Kieran Mullen

Host: Arne Schwettmann

Host: Kieran Mullen

Host: Mukremin Kilic

Host: Mukremin Kilic

Host: Mukremin Kilic

Host: Mukremin Kilic

Host: Mukremin Kilic

Host: Mukremin Kilic

Host: Kuver Sinha