arXiv subjects

Tin Seng Manfred Ho

Publications and source records attributed to Tin Seng Manfred Ho.

3 recordsLinked to original sources

arXiv2024

Intra-Family Transformation of The Bi-Te Family via in-situ Chemical Interactions

The Bi-Te binary system, characterized by the homologous series of the (Bi2)m(Bi2Te3)n, has always attracted research interest for its layered structures and potential in advanced materials applications. Despite Bi2Te3 has been extensively studied, exploration of other compounds has been constrained by synthesis challenges. This study reports the molecular beam epitaxy (MBE) growth of FeTe on Bi2Te3, demonstrating that varying growth conditions can turn the Bi2Te3 layer into different Bi-Te phases and form corresponding FeTe/Bi-Te heterostructures. Our combined analysis using reflection high-energy electron diffraction (RHEED), high-resolution X-ray diffraction (HRXRD), and high-resolution scanning transmission electron microscopy (HR-STEM), indicates that specific growth conditions used for the growth of the FeTe layer can facilitate the extraction of Te from Bi2Te3, leading to the formation of Bi4Te3 and Bi6Te3. Additionally, by lowering the FeTe growth temperature to 230 oC, Te extraction from the Bi2Te3 layer could be avoided, preserving the Bi2Te3 structure. Notably, all the three FeTe/Bi-Te structures exhibit superconductivity with the FeTe/Bi2Te3 heterostructure enjoying the highest superconductivity quality. These findings introduce a novel method for realizing Bi4Te3 and Bi6Te3 through Te extraction by growing FeTe on Bi2Te3, driven by the high reactivity between Fe and Te. This approach holds promise for synthesizing other members of the Bi-Te series, expanding the functional potential of these materials.

cond-mat.supr-con↗

arXiv2023

Proximity-induced quasi-one-dimensional superconducting quantum anomalous Hall state: a promising scalable top-down approach towards localized Majorana modes

In this work, ~100 nm wide quantum anomalous Hall insulator (QAHI) nanoribbons are etched from a two-dimensional QAHI film. One part of the nanoribbon is covered with superconducting Nb, while the other part is connected to an Au lead via two-dimensional QAHI regions. Andreev reflection spectroscopy measurements were performed, and multiple in-gap conductance peaks were observed in three different devices. In the presence of an increasing magnetic field perpendicular to the QAHI film, the multiple in-gap peak structure evolves into a single zero-bias conductance peak (ZBCP). Theoretical simulations suggest that the measurements are consistent with the scenario that the increasing magnetic field drives the nanoribbons from a multi-channel occupied regime to a single channel occupied regime, and that the ZBCP may be induced by zero energy Majorana modes as previously predicted [24]. Although further experiments are needed to clarify the nature of the ZBCP, we provide initial evidence that quasi-1D QAHI nanoribbon/superconductor heterostructures are new and promising platforms for realizing zero-energy Majorana modes.

cond-mat.supr-con↗

arXiv2022

Testing Lepton Flavor Universality at Future $Z$ Factories

As one of the hypothetical principles in the Standard Model (SM), lepton flavor universality (LFU) should be tested with a precision as high as possible such that the physics violating this principle can be fully examined. The run of $Z$ factory at a future $e^+e^-$ collider such as CEPC or FCC-$ee$ provides a great opportunity to perform this task because of the large statistics and high reconstruction efficiencies for $b$-hadrons at $Z$ pole. In this paper, we present a systematic study on the LFU test in the future $Z$ factories. The goal is three-fold. Firstly, we study the sensitivities of measuring the LFU-violating observables of $b\to c τν$, $i.e.$, $R_{J/ψ}$, $R_{D_s}$, $R_{D_s^\ast}$ and $R_{Λ_c}$, where $τ$ decays muonically. For this purpose, we develop the strategies for event reconstruction, based on the track information significantly. Secondly, we explore the sensitivity robustness against detector performance and its potential improvement with the message of event shape or beyond the $b$-hadron decays. A picture is drawn on the variation of analysis sensitivities with the detector tracking resolution and soft photon detectability, and the impact of Fox-Wolfram moments is studied on the measurement of relevant flavor events. Finally, we interpret the projected sensitivities in the SM effective field theory, by combining the LFU tests of $b\to c τν$ and the measurements of $b\to s τ^+τ^-$ and $b\to s \barν ν$. We show that the limits on the LFU-violating energy scale can be pushed up to $\sim \mathcal{O} (10)$~TeV for $\lesssim \mathcal O(1)$ Wilson coefficients at Tera-$Z$.

hep-ph↗