Public Abstract

DE-SC0020187: Symmetry Breaking in Two-Dimensional Flat-band Systems for Spin and Charge Transport

Award Status: Active

Institution: The Ohio State University, Columbus, OH
UEI: DLWBSLWAJWR1
PM: Cantoni, Claudia

Most Recent Award Date: 05/15/2026
Number of Support Periods: 8
PI: Lau, Chun Ning (Jeanie)

Current Budget Period: 06/01/2026 - 05/31/2027
Current Project Period: 08/01/2025 - 05/31/2028

Public Abstract

Symmetry Breaking in Two Dimensional Flat-band Systems for Spin, Charge and Cooper Pair Transport PI: Chun Ning (Jeanie) Lau; Co-PI: Marc Bockrath Department of Physics, Ohio State University A flat-band electronic system host very slow-moving electrons, and its properties are determined predominantly by electron-electron interactions. This leads to a plethora of many-electron quantum states including superconductivity, magnetism, integer and fractional Chern insulators and charge ordered phases, which are important for quantum technologies. Predicting emergence of these phases in a given system constitutes one of the central challenges in materials science and condensed matter physics. This program aims at addressing this challenge by exploring, understanding, and engineering these phases in flat band systems, via controlling and tuning the strength of electron-interactions. Material platforms include twisted bilayer graphene (tBLG), twisted few-layer graphene (tFLG), and Bernal-stacked multi-layer graphene. Specifically, the program consists of three thrusts, investigating superconductivity and correlated insulating states at integer and fractional fillings of the electronic bands. These states’ critical temperatures, critical fields, energy gaps, entropy, and spin and charge configurations will be examined via low temperature quantum transport measurements. Importantly, a cross-cutting theme of the program is to examine the evolution of these systems’ phase diagrams while varying their dielectric environment by coupling them to materials with tunable dielectric constant. Transport measurements will be performed while tuning a large number of experimental “knobs,” including twist angle, dielectric constant, distance to nearby gates, charge density, perpendicular displacement field, bias, temperature, and in-plane and perpendicular magnetic fields. Overall, we aim to uncover the qualitative and quantitative dependence of various correlated phases on the strength and range of interactions in addition to the hierarchy of competing symmetries and the ensuing ground states. Such knowledge will aid the distillation of general design principles and accurate prediction of emergent phases with relevance for quantum information sciences and novel nanoelectronics.

Symmetry Breaking in Two Dimensional Flat-band Systems for Spin, Charge and Cooper Pair Transport

PI: Chun Ning (Jeanie) Lau; Co-PI: Marc Bockrath

Department of Physics, Ohio State University

A flat-band electronic system host very slow-moving electrons, and its properties are determined predominantly by electron-electron interactions. This leads to a plethora of many-electron quantum states including superconductivity, magnetism, integer and fractional Chern insulators and charge ordered phases, which are important for quantum technologies. Predicting emergence of these phases in a given system constitutes one of the central challenges in materials science and condensed matter physics.

This program aims at addressing this challenge by exploring, understanding, and engineering these phases in flat band systems, via controlling and tuning the strength of electron-interactions. Material platforms include twisted bilayer graphene (tBLG), twisted few-layer graphene (tFLG), and Bernal-stacked multi-layer graphene.

Specifically, the program consists of three thrusts, investigating superconductivity and correlated insulating states at integer and fractional fillings of the electronic bands. These states’ critical temperatures, critical fields, energy gaps, entropy, and spin and charge configurations will be examined via low temperature quantum transport measurements. Importantly, a cross-cutting theme of the program is to examine the evolution of these systems’ phase diagrams while varying their dielectric environment by coupling them to materials with tunable dielectric constant. Transport measurements will be performed while tuning a large number of experimental “knobs,” including twist angle, dielectric constant, distance to nearby gates, charge density, perpendicular displacement field, bias, temperature, and in-plane and perpendicular magnetic fields.

Overall, we aim to uncover the qualitative and quantitative dependence of various correlated phases on the strength and range of interactions in addition to the hierarchy of competing symmetries and the ensuing ground states. Such knowledge will aid the distillation of general design principles and accurate prediction of emergent phases with relevance for quantum information sciences and novel nanoelectronics.