Publications
Utilizing complex oxide substrates to control carrier concentration in large-area monolayer MoS2films
Bandgap engineering is central to the design of heterojunction devices. For heterojunctions involving monolayer-thick materials like MoS2, the carrier concentration of the atomically thin film can vary significantly depending on the amount of charge transfer between MoS2 and the substrate. This makes substrates with a range of charge neutrality levels - as is the case for complex oxide substrates - a powerful addition to electrostatic gating or chemical doping to control the doping of overlying MoS2 layers.
Semiconductor-less vertical transistor with I ON/I OFF of 106
Semiconductors have long been perceived as a prerequisite for solid-state transistors. Although switching principles for nanometer-scale devices have emerged based on the deployment of two-dimensional (2D) van der Waals heterostructures, tunneling and ballistic currents through short channels are difficult to control, and semiconducting channel materials remain indispensable for practical switching. In this study, we report a semiconductor-less solid-state electronic device that exhibits an industry-applicable switching of the ballistic current.
Enhanced optical absorption in conformally grown MoS2layers on SiO2/Si substrates with SiO2nanopillars with a height of 50 nm
The integration of transition metal dichalcogenide (TMDC) layers on nanostructures has attracted growing attention as a means to improve the physical properties of the ultrathin TMDC materials. In this work, the influence of SiO2nanopillars (NPs) with a height of 50 nm on the optical characteristics of MoS2layers is investigated. Using a metal organic chemical vapor deposition technique, a few layers of MoS2were conformally grown on the NP-patterned SiO2/Si substrates without notable strain.
Topological orders competing for the Dirac surface state in FeSeTe surfaces
FeSeTe has recently emerged as a leading candidate material for the two-dimensional topological superconductivity (TSC). Two reasons for the excitement are the high Tc of the system and the fact that the Majorana zero modes (MZMs) inside the vortex cores live on the exposed surface rather than at the interface of a heterostructure as in the proximitized topological insulators. However, the recent scanning tunneling spectroscopy data have shown that, contrary to the theoretical expectation, the MZM does not exist inside every vortex core.
Modulation Doping via a Two-Dimensional Atomic Crystalline Acceptor
Two-dimensional nanoelectronics, plasmonics, and emergent phases require clean and local charge control, calling for layered, crystalline acceptors or donors. Our Raman, photovoltage, and electrical conductance measurements combined with ab initio calculations establish the large work function and narrow bands of α-RuCl3 enable modulation doping of exfoliated single and bilayer graphene, chemical vapor deposition grown graphene and WSe2, and molecular beam epitaxy grown EuS.
Opposite Polarity Surface Photovoltage of MoS2Monolayers on Au Nanodot versus Nanohole Arrays
We prepared MoS2 monolayers on Au nanodot (ND) and nanohole (NH) arrays. Both these sample arrays exhibited enhanced photoluminescence intensity compared with that of a bare SiO2/Si substrate. The reflectance spectra of MoS2/ND and MoS2/NH had clear features originating from excitation of localized surface plasmon and propagating surface plasmon polaritons. Notably, the surface photovoltages (SPV) of these hybrid plasmonic nanostructures had opposite polarities, indicating negative and positive charging at MoS2/ND and MoS2/NH, respectively.
The 2021 quantum materials roadmap
In recent years, the notion of ‘Quantum Materials’ has emerged as a powerful unifying concept across diverse fields of science and engineering, from condensed-matter and coldatom physics to materials science and quantum computing.
Slope invariant T-linear resistivity from local self-energy
A theoretical understanding of the enigmatic linear-in-temperature (T) resistivity, ubiquitous in strongly correlated metallic systems, has been a long sought-after goal. Furthermore, the slope of this robust T-linear resistivity is also observed to stay constant through crossovers between different temperature regimes: A phenomenon we dub "slope invariance."Recently, several solvable models with T-linear resistivity have been proposed, putting us in an opportune moment to compare their inner workings in various explicit calculations.
Linear resistivity and Sachdev-Ye-Kitaev (SYK) spin liquid behavior in a quantum critical metal with spin-1=2 fermions
"Strange metals" with resistivity depending linearly on temperature T down to low T have been a long-standing puzzle in condensed matter physics. Here, we consider a lattice model of itinerant spin-1=2 fermions interacting via onsite Hubbard interaction and random infinite-ranged spin-spin interaction.We show that the quantum critical point associated with the melting of the spin-glass phase by charge fluctuations displays non-Fermi liquid behavior, with local spin dynamics identical to that of the Sachdev-Ye-Kitaev family of models.