The Phonon Mediated Anomalies of Thermal Expansion in Transition-Metal Componds and Emergent Nanostructures

2016 ◽  
Vol 257 ◽  
pp. 81-85 ◽  
Author(s):  
Victor Eremenko ◽  
Valentyna Sirenko ◽  
Alexander Dolbin ◽  
Sergey Feodosyev ◽  
Igor Gospodarev ◽  
...  
Keyword(s):  
Transition Metal ◽  
Low Temperatures ◽  
Lattice Dynamics ◽  
High Temperature Superconductors ◽  
Transition Metal Dichalcogenides ◽  
Tight Binding ◽  
Harmonic Approximation ◽  
Microscopic Analysis ◽  
Complex Structures ◽  
Metal Dichalcogenides

Abstract. The negative expansion observed at low temperatures in specific crystallographic directions of complex structures with anisotropic interactions is explained by microscopic analysis within the tight-binding, quasi-harmonic approximation of lattice dynamics. The results agree with measurements on multilayer sandwiches of transition-metal dichalcogenides, high-temperature superconductors and relevant nanostructures including the carbon-based nanotubes.

scholarly journals Tunable topology and berry curvature dipole in transition metal dichalcogenide Janus monolayers

2021 ◽  
Author(s):  
Nesta Joseph ◽  
Saswata Roy ◽  
Awadhesh Narayan
Keyword(s):  
Transition Metal ◽  
Hall Effect ◽  
Transition Metal Dichalcogenides ◽  
Tight Binding ◽  
Quantum Spin ◽  
Transition Metal Dichalcogenide ◽  
Berry Curvature ◽  
Asymmetric Structures ◽  
Non Linear ◽  
Metal Dichalcogenides

Abstract Janus transition metal dichalcogenides, with intrinsic mirror asymmetry, exhibit a wide array of interesting properties. In this work, we study Janus monolayers derived from WTe2 using first-principles and tight-binding calculations. We discover that WSeTe and WSTe are topologically trivial, in contrast to the parent quantum spin Hall insulator WTe2. Motivated by the growing interest in non-linear Hall effect, which also requires asymmetric structures, we investigate the Berry curvature and its dipole in these Janus systems and find that they exhibit strikingly large values of Berry curvature dipole, despite being in the topologically trivial phase. We track down the origin of this behaviour and put forth a low-energy massive Dirac model to understand the central features of our ab inito computations. Our predictions introduce Janus monolayers as promising new platforms for exploring as well as engineering non-linear Hall effect.

scholarly journals Optically initialized robust valley-polarized holes in monolayer WSe2

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Wei-Ting Hsu ◽  
Yen-Lun Chen ◽  
Chang-Hsiao Chen ◽  
Pang-Shiuan Liu ◽  
Tuo-Hung Hou ◽  
...  
Keyword(s):  
Transition Metal ◽  
Low Temperatures ◽  
Room Temperature ◽  
Optical Pumping ◽  
Transition Metal Dichalcogenides ◽  
Kerr Rotation ◽  
Time Resolved ◽  
Recombination Lifetime ◽  
Valley Polarization ◽  
Metal Dichalcogenides

Abstract A robust valley polarization is a key prerequisite for exploiting valley pseudospin to carry information in next-generation electronics and optoelectronics. Although monolayer transition metal dichalcogenides with inherent spin–valley coupling offer a unique platform to develop such valleytronic devices, the anticipated long-lived valley pseudospin has not been observed yet. Here we demonstrate that robust valley-polarized holes in monolayer WSe2 can be initialized by optical pumping. Using time-resolved Kerr rotation spectroscopy, we observe a long-lived valley polarization for positive trion with a lifetime approaching 1 ns at low temperatures, which is much longer than the trion recombination lifetime (∼10–20 ps). The long-lived valley polarization arises from the transfer of valley pseudospin from photocarriers to resident holes in a specific valley. The optically initialized valley pseudospin of holes remains robust even at room temperature, which opens up the possibility to realize room-temperature valleytronics based on transition metal dichalcogenides.

scholarly journals Negative effective excitonic diffusion in monolayer transition metal dichalcogenides

Nanoscale ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 356-363 ◽  
Author(s):  
Roberto Rosati ◽  
Raül Perea-Causín ◽  
Samuel Brem ◽  
Ermin Malic
Keyword(s):  
Transition Metal ◽  
Low Temperatures ◽  
Effective Diffusion ◽  
Transition Metal Dichalcogenides ◽  
Spatial Profile ◽  
Intervalley Scattering ◽  
Metal Dichalcogenides

The bright exciton propagation in monolayers of transition metal dichalcogenides (TMDs) shows at low temperatures a shrinking of the spatial profile, i.e. negative effective diffusion due to intervalley scattering in the TMDs excitonic landscape.

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