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  • Séminaire des doctorants

    • Mardi 23 octobre 11:00-12:30 - Walter Escoffier - LNCMI Toulouse

      Non 1/B-periodic Shubnikov-de Haas oscillations in gate tunable 2DEG at the LaAlO3/SrTiO3 interface

      Résumé : The formation of a two-dimensional electron gas (2DEG) at the interface between two insulators SrTiO3 (STO) and LaAlO3 (LAO) is among the most intriguing finding in oxide electronics. In recent years, several exotic phenomena including super-conductivity [1], Rashba spin-orbit coupling [2], ferromagnetism and quantum oscillations [3] have been reported at this interface. While the theoretical calculations for band structure reveal the formation of several subbands (dxy, dxz and dyz) arising from the interface crystal field splitting of Ti:3d t2g orbital, no clear consensus has been reached yet from experimental evidences. Here, I investigate the quantum transport of a high mobility 2DEG at LAO/STO interface under high magnetic field (55T). Surprisingly, the Shubnikov-de Haas oscillations (SdHO) of the longitudinal resistance (Rxx) are aperiodic when plotted as a function of inverse magnetic field. This observation, at the origin of a non-linear Landau fan diagram, contrasts with a linear Hall resistance (Rxy) over the full magnetic field range. In this seminar, I will explore different scenarios to explain the peculiar transport properties of such 2DEG at LAO/STO interface. In particular, I will show that the Roth-Gao-Niu model [4], where the phase of the magnetic oscillations depends both on energy and magnetic field, provides a natural explanation of the experimental results.
      [1] A. Joshua et al., Nature Comm. 3, 1129 (2012) ; J. Biscaras et al., Phys. Rev. Lett. 108, 247004 (2012). [2] A. D. Caviglia et al., Phys. Rev. Lett. 104, 126803 (2010) ; Z. Zhong et al., Phys. Rev. B 87, 161102(R) (2013). [3] B. Shalom et al., Phys. Rev. Lett. 105, 206401 (2010) ; M. Yang et al., App. Phys. Lett. 109, 122106 (2016). [4] Y. Gao and Q. Niu, PNAS 114, 7295 (2017) ; J.N. Fuchs et al., 4 024 (2018).

      Lieu : Moyen Amphi RDC @ LPS, bât 510

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