Nontrivial doping evolution of electronic properties in Ising-superconducting alloys. (arXiv:2203.07432v1 [cond-mat.mtrl-sci])

2022-03-16T04:30:15+00:00March 16th, 2022|Categories: Publications|Tags: |

Transition metal dichalcogenides offer unprecedented versatility to engineer 2D materials with tailored properties to explore novel structural and electronic phase transitions. In this work, we present the atomic-scale evolution of the electronic ground state of a monolayer of Nb$_{1-delta}$Mo$_{delta}$Se$_2$ across the entire alloy composition range (0 < ${delta}$ < 1) using low-temperature (300 mK) scanning tunneling microscopy and spectroscopy (STM/STS). In particular, we investigate the atomic and electronic structure of this 2D alloy throughout the metal to semiconductor transition (monolayer NbSe$_2$ to MoSe$_2$). Our measurements let us extract the effective doping of Mo atoms, the bandgap evolution and the band shifts, which are monotonic with ${delta}$. Furthermore, we demonstrate that collective electronic phases (charge density wave and superconductivity) are remarkably robust against disorder. We further show that the superconducting TC changes non-monotonically with doping. This contrasting behavior in the normal and superconducting state is explained using first-principles calculations. We show that Mo doping decreases the density of states at the Fermi level and the magnitude of pair-breaking spin fluctuations as a function of Mo content. Our results paint a detailed picture of the electronic structure evolution in 2D TMD alloys, which is of utmost relevance for future 2D materials design.

Published : "arXiv Mesoscale and Nanoscale Physics".

Nontrivial doping evolution of electronic properties in Ising-superconducting alloys. (arXiv:2203.07432v1 [cond-mat.mtrl-sci])

2022-03-16T02:29:26+00:00March 16th, 2022|Categories: Publications|Tags: |

Transition metal dichalcogenides offer unprecedented versatility to engineer 2D materials with tailored properties to explore novel structural and electronic phase transitions. In this work, we present the atomic-scale evolution of the electronic ground state of a monolayer of Nb$_{1-delta}$Mo$_{delta}$Se$_2$ across the entire alloy composition range (0 < ${delta}$ < 1) using low-temperature (300 mK) scanning tunneling microscopy and spectroscopy (STM/STS). In particular, we investigate the atomic and electronic structure of this 2D alloy throughout the metal to semiconductor transition (monolayer NbSe$_2$ to MoSe$_2$). Our measurements let us extract the effective doping of Mo atoms, the bandgap evolution and the band shifts, which are monotonic with ${delta}$. Furthermore, we demonstrate that collective electronic phases (charge density wave and superconductivity) are remarkably robust against disorder. We further show that the superconducting TC changes non-monotonically with doping. This contrasting behavior in the normal and superconducting state is explained using first-principles calculations. We show that Mo doping decreases the density of states at the Fermi level and the magnitude of pair-breaking spin fluctuations as a function of Mo content. Our results paint a detailed picture of the electronic structure evolution in 2D TMD alloys, which is of utmost relevance for future 2D materials design.

Published in: "arXiv Material Science".

Photo-degradation Protection in 2D In-Plane Heterostructures Revealed by Hyperspectral Nanoimaging: the Role of Nano-Interface 2D Alloys. (arXiv:2005.11361v1 [cond-mat.mes-hall])

2020-05-26T04:31:04+00:00May 26th, 2020|Categories: Publications|Tags: , , , |

Single-layer heterostructures exhibit striking quasiparticle properties and many-body interaction effects that hold promise for a range of applications. However, their properties can be altered by intrinsic and extrinsic defects, thus diminishing their applicability. Therefore, it is of paramount importance to identify defects and understand 2D materials’ degradation over time using advanced multimodal imaging techniques as well as stabilize degradation via built-in interface protection. Here we implemented a liquid-phase precursor approach to synthesize 2D in-plane MoS2-WS2 heterostructures exhibiting nanoscale alloyed interfaces and map exotic interface effects during photo-degradation using a novel combination of hyperspectral tip-enhanced photoluminescence, Raman and near-field nanoscopy. Surprisingly, 2D alloyed regions exhibit remarkable thermal and photo-degradation stability providing protection against oxidation. Coupled with surface and interface strain, 2D alloy regions create localized potential wells that concentrate excitonic species via a charge carrier funneling effect. These results provide a clear understanding of the importance of 2D alloys as systems able to withstand degradation effects over time, and could be now used to stabilize optoelectronic devices based on 2D materials.

Published : "arXiv Mesoscale and Nanoscale Physics".

Few-layer Tin-Antimony nanosheets: A Novel 2D Alloy for Superior lithium Storage

2019-03-11T16:32:46+00:00March 11th, 2019|Categories: Publications|Tags: |

Chem. Commun., 2019, Accepted ManuscriptDOI: 10.1039/C9CC01516G, CommunicationJianan Gu, Jingui Ma, Zhiguo Du, Chao Zhang, Shubin YangA novel 2D alloy, free-standing few-layer SnSb nanosheets, is fabricated via a liquid-phase exfoliation approach. The resultant few-layer SnSb possess ultrathin feature (1-4 nm), large aspect ratios, largely exposed surfaces…The content of this RSS Feed (c) The Royal Society of Chemistry

Published in: "Chemical Communications".

Few-layer Tin-Antimony nanosheets: A Novel 2D Alloy for Superior lithium Storage

2019-03-11T16:32:46+00:00March 11th, 2019|Categories: Publications|Tags: |

Chem. Commun., 2019, Accepted ManuscriptDOI: 10.1039/C9CC01516G, CommunicationJianan Gu, Jingui Ma, Zhiguo Du, Chao Zhang, Shubin YangA novel 2D alloy, free-standing few-layer SnSb nanosheets, is fabricated via a liquid-phase exfoliation approach. The resultant few-layer SnSb possess ultrathin feature (1-4 nm), large aspect ratios, largely exposed surfaces…The content of this RSS Feed (c) The Royal Society of Chemistry

Published in: "Chemical Communications".

Lateral heterostructures of hexagonal boron nitride and graphene: BCN alloy formation and microstructuring mechanism. (arXiv:1806.03892v1 [cond-mat.mes-hall])

2018-06-12T04:30:29+00:00June 12th, 2018|Categories: Publications|Tags: , , , , |

Integration of individual two-dimensional materials into heterostructures is a crucial step which enables development of new and technologically interesting functional systems of reduced dimensionality. Here, well-defined lateral heterostructures of hexagonal boron nitride and graphene are synthesized on Ir(111) by performing sequential chemical vapor deposition from borazine and ethylene in ultra-high vacuum. Low-energy electron microscopy (LEEM) and selected-area electron diffraction ({mu}-LEED) show that the heterostructures do not consist only of hexagonal boron nitride (an insulator) and graphene (a conductor), but that also a 2D alloy made up of B, C, and N atoms (a semiconductor) is formed. Composition and spatial extension of the alloy can be tuned by controlling the parameters of the synthesis. A new method for in situ fabrication of micro and nanostructures based on decomposition of hexagonal boron nitride is experimentally demonstrated and modeled analytically, which establishes a new route for production of BCN and graphene elements of various shapes. In this way, atomically-thin conducting and semiconducting components can be fabricated, serving as a basis for manufacturing more complex devices.

Published : "arXiv Mesoscale and Nanoscale Physics".

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