Showing papers by "Chi-Cheng Lee published in 2019"
TL;DR: In this paper, the Weyl semimetal TaAs in strong magnetic field were observed to have a quasi-linear field dependent effective transverse magnetization and a non-saturating parallel magnetization when the system entered the quantum limit.
Abstract: Detecting the spectroscopic signatures of relativistic quasiparticles in emergent topological materials is crucial for searching their potential applications. Magnetometry is a powerful tool for fathoming electrons in solids, by which a clear method for discerning relativistic quasiparticles has not yet been established. Adopting the probes of magnetic torque and parallel magnetization for the archetype Weyl semimetal TaAs in strong magnetic field, we observed a quasi-linear field dependent effective transverse magnetization and a non-saturating parallel magnetization when the system enters the quantum limit. Distinct from the saturating magnetic responses for non-relativistic quasiparticles, the non-saturating signals of TaAs in strong field is consistent with our newly developed magnetization calculation for a Weyl fermion system in an arbitrary angle. Our results establish a high-field thermodynamic method for detecting the magnetic response of relativistic quasiparticles in topological materials.
23 citations
TL;DR: In this article, the authors demonstrate that the flat bands belonging to the recognized lattices can be ideally embedded into new structures that cannot be considered as the original ones in terms of a unitary transformation.
Abstract: The interplay of hopping parameters that can give rise to flat bands in consequence of quantum interference in electronic, photonic, and other interesting materials has become an extensively studied topic. Most of the recognized structures having flat bands are lattices that can be understood by the mathematical theory of line graphs, such as the Lieb, kagome, and checkerboard lattices. Here, we demonstrate that the structures that can realize the same kinds of flat bands given by those well-known lattices hosting exotic quantum phases are more flexible. The flat bands belonging to the recognized structures can be ideally embedded into new structures that cannot be considered as the original ones in terms of a unitary transformation. The uncovered mechanism enriches the understanding of physics behind the localized quantum states and broadens the choice of materials that can be used for designing electronic and photonic devices from the zero band dispersion.
12 citations
TL;DR: It was found that freshly cleaved Mn3Sn surfaces are covered with unknown clusters, and the application of voltage pulses in the tunneling condition was needed to achieve atomically flat surfaces.
Abstract: We have studied in-situ cleaved (0001) surfaces of the magnetic Weyl semimetal Mn3Sn by low-temperature scanning tunneling microscopy and spectroscopy (STM/S). It was found that freshly cleaved Mn3Sn surfaces are covered with unknown clusters, and the application of voltage pulses in the tunneling condition was needed to achieve atomically flat surfaces. STM topographs taken on the flat terrace show a bulk-terminated 1 × 1 honeycomb lattice with the Sn site brightest. First-principles calculations reveal that the brightest contrast at the Sn site originates from the surrounding surface Mn d orbitals. Tunneling spectroscopy performed on the as-cleaved and voltage-pulsed surfaces show a prominent semimetal valley near the Fermi energy.
9 citations