arXiv subjects

Joohyung Park

Publications and source records attributed to Joohyung Park.

4 recordsLinked to original sources

arXiv2024

Lifshitz Transition and Band Structure Evolution in Alkali Metal Intercalated 1Tprime-MoTe2

In van der Waals materials, coupling between adjacent layers is weak, and consequently interlayer interactions are weakly screened. This opens the possibility to profoundly modify the electronic structure, e.g., by applying electric fields or with adsorbates. Here, we show for the case of the topologically trivial semimetal 1Tprime-MoTe2 that potassium dosing at room temperature significantly transforms its band structure. With a combination of angle-resolved photoemission spectroscopy, scanning tunneling microscopy, x-ray photoemission spectroscopy, and density functional theory we show that i) for small concentrations of K, 1Tprime-MoTe2 undergoes a Lifshitz transition with the electronic structure shifting rigidly, and ii) for larger K concentrations 1Tprime-MoTe2 undergoes significant band structure transformation. Our results demonstrate that the origin of this electronic structure change stems from alkali metal intercalation.

cond-mat.mtrl-sci↗

arXiv2023

Influence of Topology on the Ultrafast Carrier Dynamics in MoTe2

Transport properties of Weyl semimetals are intimately connected to the underlying band structure. The signature of Weyl semimetals are linear dispersing bands that touch, forming Weyl points that result in high charge carrier mobilities. The layered transition metal dichalcogenide MoTe2, undergoes a temperature dependent phase transition that directly converts the trivial 1Tprime phase to the nontrivial Td phase, providing an opportunity to understand how the formation of a Weyl point manifests in the ultrafast carrier dynamics. In this study, we use resonant X-ray photoemission to monitor the element specific evolution of excited carriers 1Tprime-MoTe2 and in the vicinity of the Weyl point in Td-MoTe2. We find that the delocalization time of 1Tprime-MoTe2 is a factor 1.5 times faster than in Td-MoTe2. We argue that this is a result of the change in the density of states and screening length, to a higher carrier scattering rate in Td-MoTe2. Our study tracks the fate of carriers in MoTe2 on sub-fs time-scales and with atomic site specificity.

cond-mat.mtrl-sci↗

arXiv2023

Proximitization: Opportunities for Manipulating Correlations in Hybrid Organic / 2D Materials

Van der Waals layered and 2D materials constitute an extraordinary playground for condensed matter physics, since the strong confinement of wavefunctions to two dimensions supports a diverse set of correlated phenomena. By creating carefully designed heterostructures, these can be readily manipulated. In this Perspective, we advance the viewpoint that heterostructures from from these materials with thin layers of organic molecules offer an opportunity for creating and manipulating the correlated degrees of freedom in unprecedented ways. We briefly survey what has been accomplished thus far, including proposed mechanisms, before concentrating on unique opportunities offered by the vast selection of available organic molecules. We further introduce the notion of proximitization in combination with symmetry breaking as a fertile and potentially unifying conceptual vantage point from which to consider opportunities for tailoring correlations in van der Waals layered materials.

cond-mat.mes-hall↗

arXiv2020

Ultrafast Carrier Dynamics in Two-Dimensional Electron Gas-Like K-doped MoS2

Electronic interactions associated with atomic adsorbates on transition metal dichalcogenides such as MoS2 can induce massive electronic reconstruction that results in the formation of a new type of heavily doped transition metal dichalcogenide that exhibits characteristics of a two-dimensional electron gas. The impact of quantum confinement and reduced dimensionality on the carrier dynamics in such two-dimensional systems is at present not known, but is of paramount importance if they are to find application in optoelectronic devices. Here we show by a combination of angle-resolved photoemission and advanced x-ray spectroscopies that many-body interactions in reduced dimension drastically shorten carrier lifetimes to below 0.5 fs, and reveal how potassium intercalation in MoS2 forces orbital rehybridization to create a two-dimensional electron gas.

cond-mat.mtrl-sci↗