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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC Irvine Electronic Theses and Dissertations (2018)

In the dissertation, I show some novel experimental techniques used to measure several exotic systems. A loop-less Sagnac interferometer is used to measure time reversal symmetry breaking in the 2D unconventional superconductor BiNi and a ferromagnetic 2D electron gas between between STO and PZT. Next, ac electrical and thermal oscillations caused by a dc current across the topological Kondo insulator $SmB_6$ are measured and modeled, with very similar results. Additionally, a novel uniaxial strain technique is used on $SmB_6$ to enhance surface conduction and the band gap. This technique is further used on FQHE systems to induce meta-stable phases and anisotropic stripe phases. Finally, chiral Majorana edge modes are observed in a hybrid QAHI and superconductor system, with a potential application in quantum computing.

    Cover page: A novel approach to studying topological phases
    • Article
    • Peer Reviewed
    UC Irvine Previously Published Works (2020)
    Quantum anomalous Hall effect has been observed in magnetically doped topological insulators. However, full quantization, up until now, is limited within the sub-1 K temperature regime, although the material's magnetic ordering temperature can go beyond 100 K. Here, we study the temperature limiting factors of the effect in Cr-doped (BiSb)2Te3 systems using both transport and magneto-optical methods. By deliberate control of the thin-film thickness and doping profile, we revealed that the low occurring temperature of quantum anomalous Hall effect in current material system is a combined result of weak ferromagnetism and trivial band involvement. Our findings may provide important insights into the search for high-temperature quantum anomalous Hall insulator and other topologically related phenomena.
      Cover page: Probing the low-temperature limit of the quantum anomalous Hall effectCreative Commons 'BY' version 4.0 license
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2017)
      Majorana fermion is a hypothetical particle that is its own antiparticle. We report transport measurements that suggest the existence of one-dimensional chiral Majorana fermion modes in the hybrid system of a quantum anomalous Hall insulator thin film coupled with a superconductor. As the external magnetic field is swept, half-integer quantized conductance plateaus are observed at the locations of magnetization reversals, giving a distinct signature of the Majorana fermion modes. This transport signature is reproducible over many magnetic field sweeps and appears at different temperatures. This finding may open up an avenue to control Majorana fermions for implementing robust topological quantum computing.
        Cover page: Chiral Majorana fermion modes in a quantum anomalous Hall insulator–superconductor structureCreative Commons 'BY' version 4.0 license
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