Compass-like manipulation of electronic nematicity in Sr3Ru2O7

Funding: M.N., C.A.M. and P.W. acknowledge funding from EPSRC through EP/R031924/1 and I.B. through the International Max Planck Research School for Chemistry and Physics of Quantum Materials. L.C.R. was supported through a fellowship from the Royal Commission for the Exhibition of 1851. C.A.M. further acknowledges funding from EPSRC through EP/L015110/1.Electronic nematicity has been found in a wide range of strongly correlated electron materials, resulting in the electronic states having a symmetry that is lower than that of the crystal that hosts them. One of the most astonishing examples is Sr3Ru2O7, in which a small in-plane component of a magnetic field induces significant resistivity anisotropy. The direction of this anisotropy follows the direction of the in-plane field. The microscopic origin of this field-induced nematicity has been a long-standing puzzle, with recent experiments suggesting a field-induced spin density wave driving the anisotropy. Here, we report spectroscopic imaging of a field-controlled anisotropy of the electronic structure at the surface of Sr3Ru2O7. We track the electronic structure as a function of the direction of the field, revealing a continuous change with field angle. This continuous evolution suggests a mechanism based on spin-orbit coupling resulting in compass-like control of the electronic bands. The anisotropy of the electronic structure persists to temperatures about an order of magnitude higher compared to the bulk, demonstrating novel routes to stabilize such phases over a wider temperature range.Publisher PDFPeer reviewe

Symmetry, spin and orbital character of a van-Hove singularity in proximity to a Lifshitz transition in Sr4_4Ru3_3O10_{10}

The physics of strongly correlated electron materials is often governed by Van Hove singularities (VHss) in the vicinity of the Fermi energy. The divergence of the density of states generated by the VHss can promote electron-electron interactions and the emergence of new phases such as superconductivity, ferromagnetism, metamagnetism, nematicity and density wave orders. The shape and intensity of this divergence depends sensitively on the order and symmetry of the VHs, and hence a detailed understanding of the low-energy electronic structure is essential to understand the role of VHss in emergent phases. A family of materials with a large diversity of emergent phases that can be related to VHss close to the Fermi energy is the Ruddlesden-Popper series of the strontium ruthenates. Here we study the low-energy electronic structure at the surface of ferromagnetic Sr$_4$Ru$_3$O$_{10}$ by scanning tunneling microscopy and spectroscopy at millikelvin temperatures. We identify multiple VHss close to the Fermi energy and establish their spin character. Using quasiparticle interference we extract the orbital character and symmetry of the VHs closest to the Fermi energy, enabling us to identify a new mechanism for a field-induced Lifshitz transition facilitated by spin-orbit coupling as the origin of the metamagnetic behaviour in Sr$_4$Ru$_3$O$_{10}$.Comment: 25 pages, 5 figures and supplementary materia

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

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

重い電子系人工超格子における非従来型超伝導の制御

京都大学0048新制・課程博士博士(理学)甲第22238号理博第4552号新制||理||1654(附属図書館)京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 松田 祐司, 教授 石田 憲二, 教授 寺嶋 孝仁学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

Compass-like manipulation of electronic nematicity in Sr₃Ru₂O₇

Electronic nematicity has been found in a wide range of strongly correlated electron materials, resulting in the electronic states having a symmetry that is lower than that of the crystal that hosts them. One of the most astonishing examples is Sr3Ru2O7, in which a small in-plane component of a magnetic field induces significant resistivity anisotropy. The direction of this anisotropy follows the direction of the in-plane field. The microscopic origin of this field-induced nematicity has been a long-standing puzzle, with recent experiments suggesting a field-induced spin density wave driving the anisotropy. Here, we report spectroscopic imaging of a field-controlled anisotropy of the electronic structure at the surface of Sr3Ru2O7. We track the electronic structure as a function of the direction of the field, revealing a continuous change with field angle. This continuous evolution suggests a mechanism based on spin-orbit coupling resulting in compass-like control of the electronic bands. The anisotropy of the electronic structure persists to temperatures about an order of magnitude higher compared to the bulk, demonstrating novel routes to stabilize such phases over a wider temperature range