arXiv subjects

Yu-Chih Tseng

Publications and source records attributed to Yu-Chih Tseng.

5 recordsLinked to original sources

arXiv2024

Driving Thermoelectric Optimization in AgSbTe2 via Design of Experiments and Machine Learning

Systemic optimization of thermoelectric materials is arduous due to their conflicting electrical and thermal properties. A strategy based on Design of Experiments and machine learning is developed to optimize the thermoelectric efficiency of AgSb1+xTe2+y, an established thermoelectric. From eight experiments, high thermoelectric performance in AgSb1.021Te2.04 is revealed with a peak and average thermoelectric figure of merit of 1.61 +/- 0.24 at 600 K and 1.18 +/- 0.18 (300 - 623 K), respectively, which is over 30% higher than the best literature values for AgSb1+xTe2+y. Ag-deficiency and suppression of secondary phases in AgSb1.021Te2.04 improves the electrical properties and reduces the thermal conductivity (~0.4 W m-1 K-1). Our strategy is implemented into an open-source graphical user interface, and it can be used to optimize the methodologies, properties, and processes across different scientific fields.

cond-mat.mtrl-sci↗

arXiv2020

Efficient quantum memory for heralded single photons generated by cavity-enhanced spontaneous parametric downconversion

We interface a spontaneous parametric down conversion (SPDC) crystal and a cold atomic ensemble and demonstrate a highly efficient quantum memory through polarization-encoded single-photon qubits. Specifically, narrowband heralded single photons from a cavity-enhanced SPDC source is stored using cold atomic ensemble, with ~70% storage-and-retrieval efficiency and ~10$μ$s storage time at 50% efficiency. To prevent the degradation after storage, we also manipulate the single-photon wave profile so that the retrieved non-classical nature of single photon is preserved. On the other hand, the dual-rail storage is used for storing polarization-encoded qubits, and the corrected fidelity of flying qubits after storage reaches ~97%. The results pave the way toward large-scale quantum network.

physics.atom-ph↗

arXiv2019

Effect of laser frequency fluctuation on the decay rate of Rydberg coherence

The effect of electromagnetically induced transparency (EIT) combined with Rydberg-state atoms provides high optical nonlinearity to efficiently mediate the photon-photon interaction. However, the decay rate of Rydberg coherence, i.e., the decoherence rate, plays an important role in optical nonlinear efficiency, and can be largely influenced by laser frequency fluctuation. In this work, we carried out a systematic study of the effect of laser frequency fluctuation on the decoherence rate. We derived an analytical formula that quantitatively describes the relationship between the decoherence rate and laser frequency fluctuation. The formula was experimentally verified by using the $Λ$-type EIT system of laser-cooled $^{87}$Rb atoms, in which one can either completely eliminate or controllably introduce the effect of laser frequency fluctuation. We also included the effect of Doppler shift caused by the atomic thermal motion in the formula, which can be negligible in the $Λ$-type EIT experiment but significant in the Rydberg-EIT experiment. Utilizing the atoms of 350 $μ$K, we studied the decoherence rate in the Rydberg-EIT system involving with the state of $|32D_{5/2}\rangle$. The experimental data are consistent with the predictions from the formula. We were able to achieve a rather low decoherence rate of $2π\times$48 kHz at a moderate coupling Rabi frequency of $2π\times$4.3 MHz.

physics.atom-ph↗

arXiv2016

Modeling the band structure of the higher manganese silicides starting from Mn$_4$Si$_7$

The higher manganese silicides (HMS), with the chemical formula MnSi$_x$($x \approx 1.73 - 1.75$), have been attracted a lot of attention due to their potential application as thermoelectric materials. While the electronic band structures of HMS have been previously studied using first principle calculations, the relation between crystal structures of Mn and Si atoms and their band structures is not well understood. Here we study Mn$_4$Si$_7$ using first principle calculations and show that a half cell consisting of five Mn atoms is the essential building block for Mn$_4$Si$_7$. Using this insight, we construct a minimal tight-binding model for Mn$_4$Si$_7$ and other HMS including Mn$_{11}$Si$_{19}$ and Mn$_{15}$Si$_{26}$. The role played by the Si atoms and possible ways to achieve higher figure of merit are also discussed.

cond-mat.mtrl-sci↗

arXiv2008

Diameter-Dependent Electron Mobility of InAs Nanowires

Temperature-dependent I-V and C-V spectroscopy of single InAs nanowire field-effect transistors were utilized to directly shed light on the intrinsic electron transport properties as a function of nanowire radius. From C-V characterizations, the densities of thermally-activated fixed charges and trap states on the surface of untreated (i.e., without any surface functionalization) nanowires are investigated while enabling the accurate measurement of the gate oxide capacitance; therefore, leading to the direct assessment of the field-effect mobility for electrons. The field-effect mobility is found to monotonically decrease as the radius is reduced to sub-10 nm, with the low temperature transport data clearly highlighting the drastic impact of the surface roughness scattering on the mobility degradation for miniaturized nanowires. More generally, the approach presented here may serve as a versatile and powerful platform for in-depth characterization of nanoscale, electronic materials.

cond-mat.mtrl-sci↗