SGM 14

Non-Classical Longitudinal Magneto-Resistance in Anisotropic Black Phosphorus

Magnetoresistance (MR) is a phenomenon in which a material’s resistivity increases or decreases due to the presence of a magnetic field B. Transport measurements typically require the presence of an electric field E so as to establish an average current with charge velocity v along a preferred direction. The overall force on the charge carriers q (electrons or holes) is then simply given by the Lorentz force, F = q(E + v x B). From this stems two important limiting cases: one where the current flow is perpendicular to B and for which the magnitude contribution of the Lorentz force is maximal, and the other where it is parallel to B and there is no magnetic contribution to the Lorentz force. This simple classical picture therefore implies that MR is forbidden in the latter case. However, decades of research have shown that a material can develop a longitudinal magnetoresistance (LMR) when the current and the magnetic field are parallel. The exact set of conditions for which a non-classical LMR can or cannot be observed remains a highly debated topic which has gained renewed interest recently within the context of Weyl semimetals and topological insulators.

Pal and Maslov have studied theoretically the non-classical LMR on generic grounds, and they proposed a set of necessary and sufficient conditions within the context of Fermi surface (FS) morphology. While not all anisotropy leads to a LMR, it was shown that an angular anisotropy of the FS along the magnetic field direction is a sufficient condition. In this context, few-layer black phosphorus (bP) provides a key system for this since its Fermi surface (FS) is highly anisotropic with effective masses for holes m_ac = 0.11 m_0 and m_zz = 0.71 m_0 (m_0 is the bare electron mass) along the armchair (ac) and zigzag (zz) directions, respectively. LMR has been observed previously in bulk crystals of bP yielding only limited progress in its understanding. This is the subject of our work, where an experiment was designed to perform magneto-transport measurements in a few-layer bP device in the presence of a purely parallel magnetic field that could be rotated in the plane of the bP few-layer flake, and up to 45 T field. A strong classically-forbidden LMR was found whose non-monotonic field dependence closely matches a parabolic behavior, and whose magnitude is found to be consistent with theoretical schemes involving a FS anisotropy.


Figure 1: Polarized Raman measurement. A2g intensity as a function of incoming laser light polarization angle phi. The maximum of A2g is along the armchair axis, the minimum at -5 deg along zigzag, and therefore the S-D axis of the device is approximately aligned with the zigzag direction of the flake.


Figure 2: (a) Magneto-resistance, defined as (R(B)-R(0))/R(0), vs. the in-plane angle of rotation phi at various magnetic fields, left axis. The resistance value is displayed on the right axis. (b) Zero-field resistance value measured versus phi. In both panels, the data was taken at 323 mK temperature.


Figure 3: Magnetic-field dependence of the LMR and TMR showing distinct behaviours. It is based on the data shown in Fig. 2(a). The red line is a fit of the LMR (B parallel to I) data with a shifted parabola centred at B = 11.9 T. The blue line is a guide-to-eye for the TMR data (B perpendicular to I).

Publications:

  1. Francesca Telesio, Nicholas Hemsworth, Will Dickerson, Matei Petrescu, Vahid Tayari, Oulin Yu, David Graf, Manuel Serrano-Ruiz, Maria Caporali, Maurizio Peruzzini, Matteo Carrega, Thomas Szkopek, Stefan Heun, Guillaume Gervais: Non-Classical Longitudinal Magneto-Resistance in Anisotropic Black Phosphorus, arXiv:1808.00858 [cond-mat.mes-hall].
  2. Francesca Telesio, Nicholas Hemsworth, William Dickerson, Matei Petrescu, Vahid Tayari, Oulin Yu, David Graf, Manuel Serrano-Ruiz, Maria Caporali, Maurizio Peruzzini, Matteo Carrega, Thomas Szkopek, Stefan Heun, and Guillaume Gervais: Nonclassical Longitudinal Magnetoresistance in Anisotropic Black Phosphorus, Phys. Status Solidi RRL 14 (2020) 1900347.

Presented at:

  1. Francesca Telesio, Nicholas Hemsworth, Will Dickerson, Matei Petrescu, Vahid Tayari, Oulin Yu, David Graf, Manuel Serrano-Ruiz, Maria Caporali, Maurizio Peruzzini, Danil Bukhvalov, Thomas Szkopek, Stefan Heun, and Guillaume Gervais: Strong anisotropic in-plane magneto-transport in a few-layer bP FET, 23rd International Conference on High Magnetic Fields in Semiconductor Physics, Toulouse, France, 22 – 27 July 2018 (oral). [Abstract] [Talk]
  2. Francesca Telesio, Nicholas Hemsworth, Will Dickerson, Matei Petrescu, Vahid Tayari, Oulin Yu, David Graf, Manuel Serrano-Ruiz, Maria Caporali, Maurizio Peruzzini, Danil Bukhvalov, Thomas Szkopek, Guillaume Gervais and Stefan Heun: Strong anisotropic in-plane magnetotransport in a few-layer bP FET, 34th International conference on the physics of semiconductors, Montpellier, France, July 29 to August 3, 2018 (oral). [Abstract] [Talk]
  3. F. Telesio, N. Hemsworth, W. Dickerson, M. Petrescu, V. Tayari, Oulin Yu, D. Graf, M. Serrano-Ruiz, M. Caporali, M. Peruzzini, M. Carrega, T. Szkopek, S. Heun, and G. Gervais: Non-classical longitudinal magneto-resistance in anisotropic black phosphorus, Nanomaterials for Devices, Montreal, Canada, 10 – 12 September 2018 (invited). [Abstract] [Talk]
  4. S. Heun: Optimization of few-layer black phosphorus for low-temperature magneto-transport studies, École Polytechnique de Montréal, Quebec, Canada (Prof. O. Moutanabbir), 13 September 2018 (invited). [Abstract] [Talk]
  5. S. Heun: Optimization of few-layer black phosphorus for low-temperature magneto-transport studies, Materials.it 2018, Bologna, Italy, 22 – 26 October 2018 (invited). [Abstract] [Talk]
  6. F. Telesio, N. Hemsworth, W. Dickerson, M. Petrescu, V. Tayari, Oulin Yu, D. Graf, M. Serrano-Ruiz, M. Caporali, M. Peruzzini, M. Carrega, T. Szkopek, S. Heun, and G. Gervais: Non-classical longitudinal magneto-resistance in anisotropic black phosphorus, E-MRS Spring Meeting 2019, Nice, France, 27 – 31 May 2019 (poster). [Abstract] [Poster]