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Theory of anomalous magnetotransport from mass anisotropy

Liujun Zou, Samuel Lederer, and T. Senthil
Phys. Rev. B 95, 245135 – Published 26 June 2017
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  • INTRODUCTION
  • MODEL OF AN ANISOTROPIC FERMI POCKET
  • “FAMILIAR” REGIMES
  • “FAKE” HIGH FIELD REGIME: ωhτ≪1≪ωlτ
  • DISCUSSION
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    In underdoped YBa2Cu3O6+x, there is evidence of a small Fermi surface pocket subject to substantial mass enhancement in the doping regime 0.12<p<0.16. This mass enhancement may vary substantially over the Fermi surface, due to “hot spot” or other relevant physics. We therefore examine the magnetotransport of an electronlike Fermi pocket with large effective mass anisotropy. Within the relaxation time approximation, we show that even for a pocket with a fixed shape, the magnitude and sign of the Hall effect may change as the mass anisotropy changes (except at very large, likely inaccessible magnetic fields). We discuss implications for recent Hall measurements in near optimally doped cuprates in high fields. In addition we identify a novel intermediate asymptotic regime of magnetic field, characterized by B-linear magnetoresistance. Similar phenomena should occur in a variety of other experimental systems with anisotropic mass enhancement.

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    • Received 5 April 2017

    DOI:https://doi.org/10.1103/PhysRevB.95.245135

    ©2017 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Fermi surfaceHall effectTransport phenomena
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    Liujun Zou1,2, Samuel Lederer2, and T. Senthil2

    • 1Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
    • 2Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

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    Issue

    Vol. 95, Iss. 24 — 15 June 2017

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    Images

    • Figure 1
      Figure 1

      The simple model for the Fermi surface pocket used in these notes. It consists of several circular arcs. The light segments in green have radius kl and Fermi velocity vl, while the heavy segments in red have radius kh and Fermi velocity vh.

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    • Figure 2
      Figure 2

      Magnetic field dependence of the Hall coefficient (left) and longitudinal resistivity (right) for the model with fixed ml=me and various mh. In the calculations kh=0.2kl, the pocket is fixed to have an area of 1.9% of the Brillouin zone, and the relaxation time is τ=0.2 ps. Only when the mass enhancement is minimal is the Hall coefficient negative at all fields. For large mass enhancement a sign change in the Hall coefficient occurs at a high value of the magnetic field, for instance at ≈170 T for the case mc=8.3me shown dashed in blue. When the mass enhancement is substantial, there is also a regime of large B-linear magnetoresistance, as described in Sec. 4.

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    • Figure 3
      Figure 3

      The dependence of the Hall coefficient on approach to a QCP at which mh diverges, with ml=me held fixed. Other parameters are as in Fig. 2. Data are shown at various values of the magnetic field, showing that the sign change always precedes the QCP.

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    • Figure 4
      Figure 4

      A schematic illustration of the effects of finite temperature on the Hall coefficient under the scenario explored in this paper. A small electron pocket persists until a critical doping pc, with the Hall coefficient changing sign well below pc due to mass renormalization and curvature effects. At zero temperature, there is a sharp jump of the Hall coefficient at pc, where the electron pocket transforms into the large Fermi surface. At finite temperature, this jump is rounded, leaving a maximum in the Hall coefficient at a doping pmax<pc.

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