Abstract
Heavy-fermion metals are prototype systems for observing emergent quantum phases driven by electronic interactions 1–6. A long-standing aspiration is the dimensional reduction of these materials to exert control over their quantum phases 7–11, which remains a significant challenge because traditional intermetallic heavy-fermion compounds have three-dimensional atomic and electronic structures. Here we report comprehensive thermodynamic and spectroscopic evidence of an antiferromagnetically ordered heavy-fermion ground state in CeSiI, an intermetallic comprising two-dimensional (2D) metallic sheets held together by weak interlayer van der Waals (vdW) interactions. Owing to its vdW nature, CeSiI has a quasi-2D electronic structure, and we can control its physical dimension through exfoliation. The emergence of coherent hybridization of f and conduction electrons at low temperature is supported by the temperature evolution of angle-resolved photoemission and scanning tunnelling spectra near the Fermi level and by heat capacity measurements. Electrical transport measurements on few-layer flakes reveal heavy-fermion behaviour and magnetic order down to the ultra-thin regime. Our work establishes CeSiI and related materials as a unique platform for studying dimensionally confined heavy fermions in bulk crystals and employing 2D device fabrication techniques and vdW heterostructures 12 to manipulate the interplay between Kondo screening, magnetic order and proximity effects.
| Original language | English |
|---|---|
| Pages (from-to) | 483-488 |
| Number of pages | 6 |
| Journal | Nature |
| Volume | 625 |
| Issue number | 7995 |
| DOIs | |
| State | Published - Jan 18 2024 |
Funding
Research on 2D heavy-fermion materials was primarily supported by the US Department of Energy (DOE), Office of Science, Basic Energy Science, under award DE-SC0023406. ARPES measurements were performed at Beamline 21-ID-1 of the National Synchrotron Light Source II, a DOE Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory (Contract No. DE-SC0012704). We thank C. Petrovic and Z. Hu for their help with the sample mounting for ARPES. High-magnetic-field transport and tunnel diode oscillator measurements were performed at the National High Magnetic Field Laboratory, which is supported by the National Science Foundation (NSF; Cooperative Agreement No. DMR-1644779) and the State of Florida. Subkelvin specific heat capacity measurements (A.F.M.) were supported by the DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The specific heat analysis used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The PPMS used to perform vibrating-sample magnetometry, heat capacity and electrical transport measurements was purchased with financial support from the NSF through a supplement to award DMR-1751949. STM equipment support was provided by the Air Force Office of Scientific Research via grant FA9550-21-1-037. Electrical transport measurements of low-dimensional samples were supported by the NSF (DMR-2105048). Nano-imaging experiments and theoretical modelling were supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the DOE, Office of Science, Basic Energy Sciences (Award DE-SC0019443). The theory calculations by O.E., P.T. and C.-S.O. were supported by an ERC synergy grant (FASTCORR, project 854843), the Swedish Research Council, eSSENCE, STandUPP and the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation (KAW), the Swedish National Infrastructure for Computing, Grupos Consolidados (IT1453-22), and the German Research Foundation through the Cluster of Excellence CUI: Advanced Imaging of Matter (EXC 2056, project ID 390715994) and Project SFB-925 Light-induced Dynamics and Control of Correlated Quantum Systems (Project 170620586). V.A.P. is supported by the NSF Graduate Research Fellowship Program (NSF GRFP 2019279091). A.D. acknowledges support from the Simons Foundation Society of Fellows programme (Grant No. 855186). We acknowledge the use of facilities and instrumentation supported by the NSF through the Columbia University, Materials Research Science and Engineering Center (Grant No. DMR-2011738). The Flatiron Institute is a division of the Simons Foundation. We acknowledge support from the Max Planck–New York City Center for Non-Equilibrium Quantum Phenomena. Research on 2D heavy-fermion materials was primarily supported by the US Department of Energy (DOE), Office of Science, Basic Energy Science, under award DE-SC0023406. ARPES measurements were performed at Beamline 21-ID-1 of the National Synchrotron Light Source II, a DOE Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory (Contract No. DE-SC0012704). We thank C. Petrovic and Z. Hu for their help with the sample mounting for ARPES. High-magnetic-field transport and tunnel diode oscillator measurements were performed at the National High Magnetic Field Laboratory, which is supported by the National Science Foundation (NSF; Cooperative Agreement No. DMR-1644779) and the State of Florida. Subkelvin specific heat capacity measurements (A.F.M.) were supported by the DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The specific heat analysis used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The PPMS used to perform vibrating-sample magnetometry, heat capacity and electrical transport measurements was purchased with financial support from the NSF through a supplement to award DMR-1751949. STM equipment support was provided by the Air Force Office of Scientific Research via grant FA9550-21-1-037. Electrical transport measurements of low-dimensional samples were supported by the NSF (DMR-2105048). Nano-imaging experiments and theoretical modelling were supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the DOE, Office of Science, Basic Energy Sciences (Award DE-SC0019443). The theory calculations by O.E., P.T. and C.-S.O. were supported by an ERC synergy grant (FASTCORR, project 854843), the Swedish Research Council, eSSENCE, STandUPP and the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation (KAW), the Swedish National Infrastructure for Computing, Grupos Consolidados (IT1453-22), and the German Research Foundation through the Cluster of Excellence CUI: Advanced Imaging of Matter (EXC 2056, project ID 390715994) and Project SFB-925 Light-induced Dynamics and Control of Correlated Quantum Systems (Project 170620586). V.A.P. is supported by the NSF Graduate Research Fellowship Program (NSF GRFP 2019279091). A.D. acknowledges support from the Simons Foundation Society of Fellows programme (Grant No. 855186). We acknowledge the use of facilities and instrumentation supported by the NSF through the Columbia University, Materials Research Science and Engineering Center (Grant No. DMR-2011738). The Flatiron Institute is a division of the Simons Foundation. We acknowledge support from the Max Planck–New York City Center for Non-Equilibrium Quantum Phenomena.