Investigation of Interface Interactions Between Monolayer MoS and Metals: Implications on Strain and Surface Roughness.

Achieving a low contact resistance has been an important issue in the design of two-dimensional (2D) semiconductor-metal interfaces. The metal contact resistance is dominated by interfacial interactions. Here, we systematically investigate 2D semiconductor-metal interfaces formed by transferring monolayer MoS onto prefabricated metal surfaces, such as Au and Pd, using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and Raman spectroscopy.

Structural-disorder-driven critical quantum fluctuation and localization in two-dimensional semiconductors.

Quantum fluctuations of wavefunctions in disorder-driven quantum phase transitions (QPT) exhibit criticality, as evidenced by their multifractality and power law behavior. However, understanding the metal-insulator transition (MIT) as a continuous QPT in a disordered system has been challenging due to fundamental issues such as the lack of an apparent order parameter and its dynamical nature. Here, we elucidate the universal mechanism underlying the structural-disorder-driven MIT in 2D semiconductors through autocorrelation and multifractality of quantum fluctuations.

In-situ atomic level observation of the strain response of graphene lattice.

Strain is inevitable in two-dimensional (2D) materials, regardless of whether the film is suspended or supported. However, the direct measurement of strain response at the atomic scale is challenging due to the difficulties of maintaining both flexibility and mechanical stability at low temperature under UHV conditions. In this work, we have implemented a compact nanoindentation system with a size of [Formula: see text] 160 mm[Formula: see text] [Formula: see text] 5.

Efficient frequency conversion based on resonant four-wave mixing.

Efficient frequency conversion of photons has important applications in optical quantum technology because the frequency range suitable for photon manipulation and communication usually varies widely. Recently, an efficient frequency conversion system using a double- four-wave mixing (FWM) process based on electromagnetically induced transparency (EIT) has attracted considerable attention because of its potential to achieve a nearly 100% conversion efficiency (CE). To obtain such a high CE, the spontaneous emission loss in this resonant-type FWM system must be suppressed considerably.

Monovalent and Oriented Labeling of Gold Nanoprobes for the High-Resolution Tracking of a Single-Membrane Molecule.

Single-molecule tracking is a powerful method to study molecular dynamics in living systems including biological membranes. High-resolution single-molecule tracking requires a bright and stable signal, which has typically been facilitated by nanoparticles due to their superb optical properties. However, there are concerns about using a nanoparticle to label a single molecule because of its relatively large size and the possibility of cross-linking multiple target molecules, both of which could affect the original molecular dynamics.

High-efficiency backward four-wave mixing by quantum interference.

Electromagnetically-induced-transparency-based four-wave mixing (FWM) in a resonant four-level double-Λ system has a maximum conversion efficiency (CE) of 25% due to spontaneous emission. Herein, we demonstrate that spontaneous emission can be considerably suppressed by arranging the applied laser beams in a backward configuration. With the backward double-Λ FWM scheme, we observe a CE of 63% in cold rubidium atoms with an optical depth (OD) of 48.