1. Departments of Physics, Applied Physics, and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California 94305, USA
2. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
3. Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
4. Instituut Lorentz for Theoretical Physics, Leiden University, POB 9506, 2300 RA Leiden, The Netherlands
5. Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
6. CREST, Department of Applied Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
7. Correlated Electron Research Center, AIST, Tsukuba 305-8562, Japan

Correspondence to: N. Mannella^1,2Z.-X. Shen¹ Correspondence and requests for materials should be addressed to Z.-X.S. (Email: zxshen@stanford.edu) or N.M. (Email: NMannella@lbl.gov).

Abstract

A characteristic feature of the copper oxide high-temperature superconductors is the dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu–O bonds) directions in momentum space, generally assumed to be linked to the 'd-wave' symmetry of the superconducting state. Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction¹. Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite 'Fermi arcs'². This is the so-called pseudogap phase, and it has been assumed that it is closely linked to the superconducting state, either by assigning it to fluctuating superconductivity³ or by invoking orders which are natural competitors of d-wave superconductors^{4, 5}. Here we report experimental evidence that a very similar pseudogap state with a nodal–antinodal dichotomous character exists in a system that is markedly different from a superconductor: the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer manganite La_1.2Sr_1.8Mn₂O₇. Our findings therefore cast doubt on the assumption that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy are hallmarks of the superconductivity state.

1. Departments of Physics, Applied Physics, and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California 94305, USA
2. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
3. Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
4. Instituut Lorentz for Theoretical Physics, Leiden University, POB 9506, 2300 RA Leiden, The Netherlands
5. Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
6. CREST, Department of Applied Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
7. Correlated Electron Research Center, AIST, Tsukuba 305-8562, Japan

Correspondence to: N. Mannella^1,2Z.-X. Shen¹ Correspondence and requests for materials should be addressed to Z.-X.S. (Email: zxshen@stanford.edu) or N.M. (Email: NMannella@lbl.gov).

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