The nature of the pseudogap phase of cuprates remains a major puzzle. Although there are indications that this phase breaks various symmetries, there is no consensus on its fundamental nature 1 . Although Fermi-surface 2 , transport 3 and thermodynamic 4 signatures of the pseudogap phase are reminiscent of a transition into a phase with antiferromagnetic order 5,6 , there is no evidence for an associated long-range magnetic order. Here we report measurements of the thermal Hall conductivity κ xy in the normal state of four different cuprates (La 1.6-x Nd 0.4 Sr x CuO 4 , La 1.8-x Eu 0.2 Sr x CuO 4 , La 2-x Sr x CuO 4 , and Bi 2 Sr 2-x La x CuO 6+δ ) and show that a large negative κ xy signal is a property of the pseudogap phase, appearing with the onset of that phase at the critical doping p*. Since it is not due to charge carriersas it persists when the material becomes an insulator, at low doping -or magnons -as it exists in the absence of magnetic order -or phonons -since skew scattering
We report on spin transport in state-of-the-art epitaxial monolayer graphene based 2D-magnetic tunnel junctions (2D-MTJs). In our measurements, supported by ab-initio calculations, the strength of interaction between ferromagnetic electrodes and graphene monolayers is shown to fundamentally control the resulting spin signal. In particular, by switching the graphene/ferromagnet interaction, spin transport reveals magneto-resistance signal MR > 80% in junctions with low resistance × area products. Descriptions based only on a simple K-point filtering picture (i.e. MR increase with the number of layers) are not sufficient to predict the behavior of our devices. We emphasize that hybridization effects need to be taken into account to fully grasp the spin properties (such as spin dependent density of states) when 2D materials are used as ultimately thin interfaces. While this is only a first demonstration, we thus introduce the fruitful potential of spin manipulation by proximity effect at the hybridized 2D material / ferromagnet interface for 2D-MTJs.
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