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(線上演講 online talk) Charge transport in quasi-one-dimensional nanoscale systems

演講者 : Dr. Chen-Hsuan Hsu (徐晨軒) (Research Scientist) (RIKEN Center for Emergent Matter Science, Japan)
演講時間 : 2021 / 12 / 21 15:30
理學教學新大樓 2F 前沿量子中心演講廳
Quasi-one-dimensional channels appear in various nanoscale systems, such as nanowires, nanotubes, and boundaries of topological insulating materials. Recently, these systems have drawn great attention due to their potential for stabilizing Majorana zero modes [1-4], which can be utilized to form quantum bits as elements for quantum computation. In these systems, charge transport provides a straightforward way to probe and characterize the channels. In this talk, I will summarize my works on charge transport properties of quasi-one-dimensional channels in helical and nonhelical systems. First, I discuss topological boundary channels, in which helical liquids emerge as a result of spin-momentum locking and Coulomb interaction between electrons [5]. While the channel conductance was expected to be quantized in the absence of spin-flip elastic backscattering, magnetic impurities including nuclear spins [6,7] or other resistance sources [5] can lead to a substantial conductance deviation in realistic samples. In consequence, the conductance can be suppressed at low temperatures in long samples, placing a fundamental limitation in scalable architectures. In the second part of the talk, I will turn to nonhelical channels in the presence of a helical field and discuss transport features when the lowest two transverse subbands are populated. Due to the interplay between Coulomb interaction and the helical field, novel backscattering processes arise. They result in scattering resonances and partial gaps in the energy spectrum, thus leading to unusual conductance plateaus and dips [8]. Remarkably, the positions and values of the dips are independent of specific material parameters. These universal conductance dips indicate formation of strongly correlated fermion systems hosting fractional excitations, resembling the fractional quantum Hall states.
References:
[1] Chen-Hsuan Hsu et al., Phys. Rev. Lett. 121, 196801 (2018).
[2] Chen-Hsuan Hsu et al., Phys. Rev. B 92, 235435 (2015).
[3] Chen-Hsuan Hsu et al., Phys. Rev. B 100, 195423 (2019).
[4] Yosuke Sato, Sadashige Matsuo, Chen-Hsuan Hsu et al., Phys. Rev. B 99, 155304 (2019).
[5] Chen-Hsuan Hsu et al., Semicond. Sci. Technol. 36, 123003 (2021).
[6] Chen-Hsuan Hsu et al., Phys. Rev. B 96, 081405(R) (2017).
[7] Chen-Hsuan Hsu et al., Phys. Rev. B 97, 125432 (2018).
[8] Chen-Hsuan Hsu et al., Phys. Rev. Research 2, 043208 (2020).