Abstract
The highest superconducting transition temperatures in the cuprates are achieved in bilayer and trilayer systems, highlighting the importance of interlayer interactions for high Tc. It has been argued that interlayer hybridization vanishes along the nodal directions by way of a specific pattern of orbital overlap. Recent quantum oscillation measurements in bilayer cuprates have provided evidence for a residual bilayer-splitting at the nodes that is sufficiently small to enable magnetic breakdown tunneling at the nodes. Here we show that several key features of the experimental data can be understood in terms of weak spin-orbit interactions naturally present in bilayer systems, whose primary effect is to cause the magnetic breakdown to be accompanied by a spin flip. These features can now be understood to include the equidistant set of three quantum oscillation frequencies, the asymmetry of the quantum oscillation amplitudes in c-axis transport compared to ab-plane transport, and the anomalous magnetic field angle dependence of the amplitude of the side frequencies suggestive of small effective g-factors. We suggest that spin-orbit interactions in bilayer systems can further affect the structure of the nodal quasiparticle spectrum in the superconducting phase. PACS numbers: 71.45.Lr, 71.20.Ps, 71.18.+y
Highlights
Pockets, together with a schematic of some of the magnetic breakdown combination orbits resulting from a small residual bilayer-splitting along the nodal directions
Interference between two linearly Zeeman-split components of a cyclotron orbit in a magnetic field suppresses the quantum oscillation amplitude by a factor πm g eff 2me cos θ that depends on the ratio of Zeeman energy geffμBB to the cyclotron energy ωc = eB cos θ/m27
We have shown that anomalously small effective g-factors for the side frequencies originate from combination orbits in which traversal of the nodal region is accompanied by a spin-flip
Summary
Pockets, together with a schematic of some of the magnetic breakdown combination orbits resulting from a small residual bilayer-splitting along the nodal directions (indicated by dotted lines). Combination orbits resulting from magnetic breakdown in which the tunneling of electrons across a small residual gap separating bilayer-split Fermi surfaces (see Fig. 1b) can naturally account for such an equidistant set of frequencies[25,26]. A close examination of the angle-dependent measurements of quantum oscillations in YBa2Cu3O6+x (see Fig. 2) suggests an anomalously small effective g-factor for these side frequencies[26], which is atypical for a 3d transition metal system. We show that spin-orbit interactions, naturally present in bilayer crystalline systems, provide just such a mechanism It enables an understanding of the observed anomalously small effective g-factors of the side frequencies, as well as several other key features of the experimental quantum oscillation data
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