Public Abstract

DE-SC0023406: Van der Waals Rare Earth Materials: Heavy Fermions and Beyond

Award Status: Active

Institution: The Trustees of Columbia University in the City of New York (Morningside Campus), New York, NY
UEI: F4N1QNPB95M4
DUNS: 049179401

Most Recent Award Date: 09/19/2025
Number of Support Periods: 4
PM: Cantoni, Claudia

Current Budget Period: 09/01/2025 - 08/31/2026
Current Project Period: 09/01/2025 - 08/31/2026
PI: Roy, Xavier

Supplement Budget Period: N/A

Public Abstract

Van der Waals Rare Earth Materials: Heavy Fermions and Beyond Xavier Roy, Department of Chemistry, Columbia University (Principal Investigator) Abhay Pasupathy, Department of Physics, Columbia University (Co-Investigator) Strong interactions among electrons in quantum materials can give rise to rich and unexpected behavior. This project investigates a new family of two-dimensional metals composed of rare earth elements, where localized f-electron magnetic moments hybridize with mobile conduction electrons to form “heavy” quasiparticles known as heavy fermions. Confining these heavy fermions in two dimensions within layered materials enables unprecedented control over magnetic order, electronic correlations, and quantum fluctuations—achieved by tuning layer thickness, applying gate voltages, or stacking dissimilar crystals. This team recently discovered CeSiI, the first layered intermetallic compound that retains heavy-electron behavior down the two-dimensional limit. Scanning tunneling microscopy, transport measurements, and spectroscopy revealed striking phenomena: directional Kondo hybridization, coexistence of antiferromagnetism with a dense heavy-electron fluid, and emergent complex magnetic structures. These findings raise fundamental questions about their origins and implications, which this renewal project seeks to address. Building on this foundation, the research will systematically explore the magnetic and electronic properties of CeSiI and related two-dimensional heavy fermion systems using chemical tuning, scanning probes, neutron and X-ray scattering, and optical spectroscopy. New methods will be developed to assemble heterostructures with atomic precision. In parallel, novel families of layered rare-earth intermetallics will be designed and synthesized to strengthen correlations, access new dimensional regimes, and generate unconventional magnetic ground states. Through the integration of crystal growth, low-temperature experimentation, transport studies, and theoretical modeling, the project aims to uncover the governing principles of correlated electrons in two dimensions. These insights will deepen fundamental understanding of quantum magnetism and emergent electronic phases, while laying the groundwork for future devices that leverage the unique properties of two-dimensional heavy fermions. The effort will be led by PI Roy and co-PI Pasupathy, combining expertise in solid-state chemistry, magnetism, scanning tunneling microscopy, spectroscopy, and transport. Strong collaborations with experts in theory, optical and X-ray spectroscopy, and neutron scattering will enhance the program’s reach. The integrated approach will drive progress in two-dimensional quantum materials and advance the broader field of strongly correlated systems.

Van der Waals Rare Earth Materials: Heavy Fermions and Beyond

Xavier Roy, Department of Chemistry, Columbia University (Principal Investigator)

Abhay Pasupathy, Department of Physics, Columbia University (Co-Investigator)

Strong interactions among electrons in quantum materials can give rise to rich and unexpected behavior. This project investigates a new family of two-dimensional metals composed of rare earth elements, where localized f-electron magnetic moments hybridize with mobile conduction electrons to form “heavy” quasiparticles known as heavy fermions. Confining these heavy fermions in two dimensions within layered materials enables unprecedented control over magnetic order, electronic correlations, and quantum fluctuations—achieved by tuning layer thickness, applying gate voltages, or stacking dissimilar crystals.

This team recently discovered CeSiI, the first layered intermetallic compound that retains heavy-electron behavior down the two-dimensional limit. Scanning tunneling microscopy, transport measurements, and spectroscopy revealed striking phenomena: directional Kondo hybridization, coexistence of antiferromagnetism with a dense heavy-electron fluid, and emergent complex magnetic structures. These findings raise fundamental questions about their origins and implications, which this renewal project seeks to address.

Building on this foundation, the research will systematically explore the magnetic and electronic properties of CeSiI and related two-dimensional heavy fermion systems using chemical tuning, scanning probes, neutron and X-ray scattering, and optical spectroscopy. New methods will be developed to assemble heterostructures with atomic precision. In parallel, novel families of layered rare-earth intermetallics will be designed and synthesized to strengthen correlations, access new dimensional regimes, and generate unconventional magnetic ground states.

Through the integration of crystal growth, low-temperature experimentation, transport studies, and theoretical modeling, the project aims to uncover the governing principles of correlated electrons in two dimensions. These insights will deepen fundamental understanding of quantum magnetism and emergent electronic phases, while laying the groundwork for future devices that leverage the unique properties of two-dimensional heavy fermions.

The effort will be led by PI Roy and co-PI Pasupathy, combining expertise in solid-state chemistry, magnetism, scanning tunneling microscopy, spectroscopy, and transport. Strong collaborations with experts in theory, optical and X-ray spectroscopy, and neutron scattering will enhance the program’s reach. The integrated approach will drive progress in two-dimensional quantum materials and advance the broader field of strongly correlated systems.