Tunneling Spectroscopy of Quantum Materials

How can one control electronic structure just with magnetic fields? In our new paper, we track how the electronic structure in Sr₃Ru₂O₇ changes as a function of applied field direction, providing direct imaging of a field-controlled nematicity and how to control electronic structure with surprisingly modest magnetic fields. Also another good example of how the surface can differ subtly from what the bulk does …

Read more in Masahiro and Isidor’s paper:
Masahiro Naritsuka, Izidor Benedičič, Luke C. Rhodes, Carolina A. Marques, Christopher Trainer, Zhiwei Li, Alexander C. Komarek, and Peter Wahl, Compass-like manipulation of electronic nematicity in Sr₃Ru₂O₇, Proc. Nat. Acad. Sci. 120, e2308972120 (2023), arxiv/2305.11210.

Read in our new study, led by Steve Lee’s group combining μSR with STM by Chi Ming and Christopher and theory, what evidence there is for triplet pairs due to spin-orbit coupling and proximity effect in heterostructures of Platinum and Niobium.

Original publication:
M. Flokstra, R. Stewart, C.-M. Yim, C. Trainer, P. Wahl, D. Miller, N. Satchell, G. Burnell, H. Luetkens, T. Prokscha, A. Suter, E. Morenzoni, S. Lee, Spin-orbit driven superconducting proximity effects in Pt/Nb thin films, Nat. Commun. 14, 5081 (2023).

Congratulations to Seohyun, Rebecca and Lewis to their graduation this week and great results in their final year projects! Looking forward to welcome and work with Rebecca and Seohyun as PhD students in the School from September, Rebecca in the group and Seohyun with Bernd Braunecker and Luke Rhodes.

Read in our new preprint by Masahiro and Izidor about how we can control nematicity in the surface layer of Sr₃Ru₂O₇ by vector magnetic fields. Dependent on the direction of the applied field, we find checkerboard charge modulations, nematicity and stripe modulations which can all be explained from a minimal tight-binding model that accounts for magnetism and spin-orbit coupling. Key open question: can the same minimal model explain the behaviour in the polarized phase in the bulk?

Full reference:
M. Naritsuka, I. Benedičič, L.C. Rhodes, C.A. Marques, C. Trainer, Z. Li, A.C. Komarek, and P. Wahl, Compass-like manipulation of electronic nematicity in Sr₃Ru₂O₇, arxiv/2305.11210.

Read in Carolina’s new preprint on the Van Hove singularity in Sr₄Ru₃O₁₀ how we can use quasi-particle interference imaging to identify its symmetry, spin and orbital character. Our results hint at a new mechanism for a magnetic-field-driven Lifshitz transition.

Full reference:
C.A. Marques, W. Osmolska, I. Benedičič, L.C. Rhodes, M. Naritsuka, R. Arumugam, V. Granata, R. Fittipaldi, A. Vecchione, and P. Wahl, Symmetry, spin and orbital character of a Van-Hove singularity in proximity to a Lifshitz transition in Sr₄Ru₃O₁₀, arxiv/2303.05587.

Meet members of the group and hear about our research at the following contributions at the APS March meeting in Las Vegas:

• Olivia Armitage on Wd, March 8, 1:18pm, Room 305 on Scanning tunnelling microscopy of a two-dimensional magnetic material
• Peter Wahl on Th, March 9, 9:48am, Room 221 on Spectroscopic imaging of a magnetic-field-induced Lifshitz transition in Sr₃Ru₂O₇
• Izidor Benedičič on Fri, March 10, 10:12am, Room 305 on Compass-like manipulation of electronic structure in Sr₃Ru₂O₇

For some shapes, we can relatively easily infer what their 3D shape will have been from only looking at their 2D projections – at least for some directions. Read in Luke’s new paper in Phys. Rev. B to find out how this works for Quasiparticle Interference Imaging in cases where we probe a three-dimensional electronic structure at the surface of the material.

Original reference:
Luke C. Rhodes, Weronika Osmolska, Carolina A. Marques, and Peter Wahl, Nature of quasiparticle interference in three dimensions, Phys. Rev. B 107, 045107 (2023).

Metamagnetic materials, like Sr₄Ru₃O₁₀, have potential applications for spintronics and novel information technologies, which involves using the spin of electrons in devices. In this study, we used advanced spectroscopic techniques to investigate Sr₄Ru₃O₁₀ and understand between the electronic structure, crystal symmetries, spin-orbit coupling and magnetism. We used low temperature scanning tunneling microscopy and spectroscopy to study the material’s metamagnetism. Our results provide new insights into how the electronic structure of Sr₄Ru₃O₁₀ influences its properties, which could potentially be useful for developing new spintronic devices.

Read more in our paper in Phys. Rev. B.

How does a Lifshitz transition look like in real space? Cool data hot off the press in Carolina and Luke’s new paper in Science Advances (here), imaging a magnetic-field induced Lifshitz transition in the surface layer of Sr₃Ru₂O₇ with our millikelvin STM. Lot’s of new puzzles. For example, why do stripes appear in magnetic field? Why is QPI so anisotropic? What does the behaviour of the surface tell us about the bulk? Stay tuned for more!

Can we link the shape of a domain wall in a van der Waals (vdW) ferromagnet to microscopic interaction parameters? Yes we can! Read our new paper to find out how we can link the details of the magnon dispersion from neutron scattering to the shape of a domain wall as measured by spin-polarized STM in the vdW ferromagnetic metal Fe_3-xGeTe₂.

C. Trainer et al., Physical Review B 106, L081405 (2022).