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Feng, Lei

Publications and source records attributed to Feng, Lei.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Pressure‐Induced Metallization and Isostructural Transitions in 3R‐MoS2

At ambient conditions 3R-polytypes of transition metal dichalcogenides (TMDs) demonstrate fascinating properties because of their unique layer stacking. Understanding the structure-property relationship is essential for the realization of their use in spintronic, valleytronic, and optoelectronic applications. Herein, after the high pressure-temperature synthesis of 3R-MoS2 in a large volume cubic press, a concomitant experimental and theoretical high-pressure study of 3R-MoS2 is reported, leading to the discovery of pressure-induced reversible isostructural phase transitions without symmetry breaking. Concurrent with the isostructural transitions, a semiconductor-to-metal transition is observed, owing to strong interlayer interaction and charge redistribution across the van der Waals gap under pressure. The pressure-induced enhancement of interlayer interactions together with the robust intrinsic layer stacking in 3R-MoS2 prevent the layers from sliding under pressure and hinder a corresponding volume collapse. This study on continuous pressure-tuning of crystal and electronic structure in 3R-MoS2 will play a vital role in developing the next-generation devices involving coupling of structural, optical, and electrical properties of 3R-polytypes of TMDs and other layered materials.

Ahmad, Azkar Saeed↗
DOE OSTI2023

Interactive cryptographic proofs of quantumness using mid-circuit measurements

The ability to perform measurements in the middle of a quantum circuit is a powerful resource. It underlies a wide range of applications, from remote state preparation to quantum error correction. Here we apply mid-circuit measurements for a particular task: demonstrating quantum computational advantage. The goal of such a demonstration is for a quantum device to perform a computational task that is infeasible for a classical device with comparable resources. In contrast to existing demonstrations, the distinguishing feature of our approach is that the classical verification process is efficient, both in asymptotic complexity and in practice. Furthermore, the classical hardness of performing the task is based upon well-established cryptographic assumptions. Protocols with these features are known as cryptographic proofs of quantumness. Using a trapped-ion quantum computer, we perform mid-circuit measurements by spatially isolating portions of the ion chain via shuttling. This enables us to implement two interactive cryptographic proofs of quantumness, which when suitably scaled to larger systems, promise the efficient verification of quantum computational advantage. In conclusion, our methods can be applied to a range of interactive quantum protocols.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Alpha-decay induced shortening of fission tracks simulated by in situ ion irradiation

The diffusion of defects (e.g., vacancies and interstitials) and elements used for dating (e.g., He and Pb) in a mineral structure is a thermal process: This is the primary assumption used to determine the age and thermal history of minerals. For instance, thermal history reconstruction, through the number and length distribution of tracks produced by spontaneous fission of 238 U, is obtained by assuming a thermal event to be the only energy source for shortening of fission tracks. Here, we report a new, non-thermal energy source that induces additional shortening of fission tracks by the irradiation of alpha-recoils from the alpha-decay of 238 U and 232 Th. We simulate alpha-decay induced track-shortening by combining ion accelerator irradiations with transmission electron microscopy. This allows for the first observation of track-shrinkage during in situ ion irradiation. We show that rather than alpha-particles, alpha-recoils induce a significant shortening of fission tracks by nuclear-collisions. The shortening of track-length can be quantified as a function of alpha-decay event dose. However, apatite is less sensitive than zircon to this non-thermal process. Furthermore, the findings exemplify the interactions among different types of self-irradiation from alpha-particles, alpha-recoils and fission-fragment nuclei in single mineral grains and have important implications for the use of zircon and apatite for radiometric dating and thermochronology.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Jet Substructure in Fireworks Emission from Nonuniform and Rotating Bose-Einstein Condensates

Here, we show that jet emission from a Bose condensate with periodically driven interactions, also known as “Bose fireworks”, contains essential information on the condensate wave function, which is difficult to obtain using standard detection methods. We illustrate the underlying physics with two examples. When condensates acquire phase patterns from external potentials or from vortices, the jets display novel substructure, such as oscillations or spirals, in their correlations. Through a comparison of theory, numerical simulations, and experiments, we show how one can quantitatively extract the phase and the helicity of a condensate from the emission pattern. Our work, demonstrating the strong link between jet emission and the underlying quantum system, bears on the recent emphasis on jet substructure in particle physics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗