Atomic-scale imaging of emergent order at a magnetic-field-induced Lifshitz transition

Funding: UK Engineering and Physical Sciences Research Council, Funder ID: (FUNDREF) 10.13039/501100000266, Grant: EP/L015110/1. UK Engineering and Physical Sciences Research Council, Funder ID:(FUNDREF) 10.13039/501100000266, Grant: EP/R031924/1. Engineering and Physical Sciences Research Council, Funder ID:(FUNDREF) 10.13039/501100000266, Grant: EP/R023751/1. Engineering and Physical Sciences Research Council, Funder ID:(FUNDREF) 10.13039/501100000266, Grant: EP/L017008/1.The phenomenology and radical changes seen in material properties traversing a quantum phase transition have captivated condensed matter research over the past decades. Strong electronic correlations lead to exotic electronic ground states, including magnetic order, nematicity, and unconventional superconductivity. Providing a microscopic model for these requires detailed knowledge of the electronic structure in the vicinity of the Fermi energy, promising a complete understanding of the physics of the quantum critical point. Here, we demonstrate such a measurement at the surface of Sr3Ru2O7. Our results show that, even in zero field, the electronic structure is strongly C2 symmetric and that a magnetic field drives a Lifshitz transition and induces a charge-stripe order. We track the changes of the electronic structure as a function of field via quasiparticle interference imaging at ultralow temperatures. Our results provide a complete microscopic picture of the field-induced changes of the electronic structure across the Lifshitz transition.Publisher PDFPeer reviewe

Relating spin-polarized STM imaging and inelastic neutron scattering in the van-der-Waals ferromagnet Fe3GeTe2

C.T. and P.W. acknowledge funding through Grants No. EP/R031924/1 and No. EP/T031441/1, L.C.R. through the Royal Commission for the Exhibition of 1851, I.B. through the International Max Planck Research School for Chemistry and Physics of Quantum Materials, and H.L. through the ISIS facility development studentship program.Van-der-Waals (vdW) ferromagnets have enabled the development of heterostructures assembled from exfoliated monolayers with spintronics functionalities, making it important to understand and ultimately tune their magnetic properties at the microscopic level. Information about the magnetic properties of these systems comes so far largely from macroscopic techniques, with little being known about the microscopic magnetic properties. Here, we combine spin-polarized scanning tunneling microscopy and quasi-particle interference imaging with neutron scattering to establish the magnetic and electronic properties of the metallic vdW ferromagnet Fe3GeTe2. By imaging domain walls at the atomic scale, we can relate the domain wall width to the exchange interaction and magnetic anisotropy extracted from the magnon dispersion as measured in inelastic neutron scattering, with excellent agreement between the two techniques. From comparison with Density Functional Theory calculations we can assign the quasi-particle interference to be dominated by spin-majority bands. We find a dimensional dichotomy of the bands at the Fermi energy: bands of minority character are predominantly two-dimensional in character, whereas the bands of majority character are three-dimensional. We expect that this will enable new design principles for spintronics devices.Publisher PDFPeer reviewe

Interplay of ferromagnetism and spin-orbit coupling in Sr4Ru3O10

Funding: IB acknowledges funding through the International Max Planck Research School for Chemistry and Physics of Quantum Materials, MN, CT and PW through EP/R031924/1 and EP/T031441/1 and LCR from the Royal Commission of the Exhibition of 1851. TEM measurements were supported through grants EP/R023751/1, EP/L017008/1 and EP/T019298/1. YN acknowledges support through the ERC grant ERC-714193-QUESTDO held by Phil King.The ground state of metamagnetic materials can be controlled by magnetic field, promising new functionalities for spintronics applications. Yet, a microscopic understanding of the interplay of the electronic structure with the susceptibility to emergent orders is often missing, but would greatly facilitate optimization of the properties of metamagnetic materials. Here, we use low temperature scanning tunneling microscopy (STM) and spectroscopy to study the metamagnetism in the trilayer ruthenate Sr4Ru3O10, combining STM-based magnetostriction measurements with quasiparticle-interference imaging (QPI) to elucidate the role of the microscopic electronic structure in the macroscopic metamagnetic properties. Our results highlight the importance of the orthorhombicity of the material for its metamagnetic properties, confirmed by magnetization measurements. Our QPI results show clear signatures of the minority spin bands crossing the Fermi energy, and provide a link between the ferromagnetic properties, spin-orbit coupling and the orthorhombicity of the crystal structure.PostprintPeer reviewe

Spin-orbit coupling induced Van Hove singularity in proximity to a Lifshitz transition in Sr4Ru3O10

Funding: CAM, MN and PW gratefully acknowledge funding from the Engineering and Physical Sciences Research Council through EP/R031924/1 and EP/S005005/1, IB through the International Max Planck Research School for Chemistry and Physics of Quantum Materials and LCR from a fellowship from the Royal Commission of the Exhibition of 1851. RA, RF and AV thank the EU’s Horizon 2020 research and innovation program under Grant Agreement No. 964398 (SUPERGATE).Van Hove singularities (VHss) in the vicinity of the Fermi energy often play a dramatic role in the physics of strongly correlated electron materials. The divergence of the density of states generated by VHss can trigger the emergence of new phases such as superconductivity, ferromagnetism, metamagnetism, and density wave orders. A detailed understanding of the electronic structure of these VHss is therefore essential for an accurate description of such instabilities. Here, we study the low-energy electronic structure of the trilayer strontium ruthenate Sr4Ru3O10, identifying a rich hierarchy of VHss using angle-resolved photoemission spectroscopy and millikelvin scanning tunneling microscopy. Comparison of k-resolved electron spectroscopy and quasiparticle interference allows us to determine the structure of the VHss and demonstrate the crucial role of spin-orbit coupling in shaping them. We use this to develop a minimal model from which we identify a new mechanism for driving a field-induced Lifshitz transition in ferromagnetic metals.Peer reviewe

Relating spin-polarized STM imaging and inelastic neutron scattering in the van-der-Waals ferromagnet Fe₃GeTe₂

Van-der-Waals (vdW) ferromagnets have enabled the development of heterostructures assembled from exfoliated monolayers with spintronics functionalities, making it important to understand and ultimately tune their magnetic properties at the microscopic level. Information about the magnetic properties of these systems comes so far largely from macroscopic techniques, with little being known about the microscopic magnetic properties. Here, we combine spin-polarized scanning tunneling microscopy and quasi-particle interference imaging with neutron scattering to establish the magnetic and electronic properties of the metallic vdW ferromagnet Fe3GeTe2. By imaging domain walls at the atomic scale, we can relate the domain wall width to the exchange interaction and magnetic anisotropy extracted from the magnon dispersion as measured in inelastic neutron scattering, with excellent agreement between the two techniques. From comparison with Density Functional Theory calculations we can assign the quasi-particle interference to be dominated by spin-majority bands. We find a dimensional dichotomy of the bands at the Fermi energy: bands of minority character are predominantly two-dimensional in character, whereas the bands of majority character are three-dimensional. We expect that this will enable new design principles for spintronics devices

Data underpinning Izidor Benedicic's thesis

The data files are embargoed until 18/10/2025