scholarly journals Giant gate-tunable bandgap renormalization and excitonic effects in a 2D semiconductor

2019 ◽  
Vol 5 (7) ◽  
pp. eaaw2347 ◽  
Author(s):  
Zhizhan Qiu ◽  
Maxim Trushin ◽  
Hanyan Fang ◽  
Ivan Verzhbitskiy ◽  
Shiyuan Gao ◽  
...  
Keyword(s):  
Binding Energy ◽  
Single Layer ◽  
Scanning Tunneling Spectroscopy ◽  
Binding Energies ◽  
Exciton Binding Energy ◽  
Scanning Tunneling ◽  
Full Potential ◽  
2D Semiconductors ◽  
Wide Range ◽  
Excitonic Effects

Understanding the remarkable excitonic effects and controlling the exciton binding energies in two-dimensional (2D) semiconductors are crucial in unlocking their full potential for use in future photonic and optoelectronic devices. Here, we demonstrate large excitonic effects and gate-tunable exciton binding energies in single-layer rhenium diselenide (ReSe2) on a back-gated graphene device. We used scanning tunneling spectroscopy and differential reflectance spectroscopy to measure the quasiparticle electronic and optical bandgap of single-layer ReSe2, respectively, yielding a large exciton binding energy of 520 meV. Further, we achieved continuous tuning of the electronic bandgap and exciton binding energy of monolayer ReSe2 by hundreds of milli–electron volts through electrostatic gating, attributed to tunable Coulomb interactions arising from the gate-controlled free carriers in graphene. Our findings open a new avenue for controlling the bandgap renormalization and exciton binding energies in 2D semiconductors for a wide range of technological applications.

scholarly journals Dielectric Screening Modulates Semicondcutor Nanoplatelet Excitons

2021 ◽  
Author(s):  
Ashley Shin ◽  
Azmain A. Hossain ◽  
Stephanie M. Tenney ◽  
Xuanheng Tan ◽  
Lauren A. Tan ◽  
...  
Keyword(s):  
Binding Energy ◽  
Relative Effect ◽  
Binding Energies ◽  
Exciton Binding Energy ◽  
Electrostatic Model ◽  
Excitonic Absorption ◽  
2D Semiconductors ◽  
Dielectric Screening ◽  
Device Properties ◽  
First Time

The influence of external dielectric environments is well understood for 2D semiconductor materials but is overlooked for colloidally-grown II-VI nanoplatelets (NPLs). In this work, we synthesize MX (M=Cd, Hg; X= Se, Te) NPLs of varying thicknesses, and apply a modified Elliott model to fit excitonic absorption features and report exciton binding energies for cadmium telluride and mercury chalcogenides for the first time. Our observations indicate that the exciton binding energy is modulated by the dielectric screening of semiconductor material by the external ligand environment. Furthermore, NPL binding energies show a dependence on the number of monolayers consistent with relative effect of internal vs. external dielectric. To describe this, we derive an analytical electrostatic model, reinforcing the hypothesis that the external environment increases the exciton binding energy relative to the bulk—due to the distortion of the Coulombic potential across the NPL surface. We further confirm this effect by decreasing and recovering the exciton binding energy of HgTe NPLs through washing in polarizable solvents. Our results illustrate that NPLs are colloidal analogues of Van der Waals 2D semiconductors and point to surface modification as an approach to control photophysics and device properties.

scholarly journals Dielectric Screening Modulates Semicondcutor Nanoplatelet Excitons

2021 ◽  
Author(s):  
Ashley Shin ◽  
Azmain A. Hossain ◽  
Stephanie M. Tenney ◽  
Xuanheng Tan ◽  
Lauren A. Tan ◽  
...  
Keyword(s):  
Binding Energy ◽  
Relative Effect ◽  
Binding Energies ◽  
Exciton Binding Energy ◽  
Electrostatic Model ◽  
Excitonic Absorption ◽  
2D Semiconductors ◽  
Dielectric Screening ◽  
Device Properties ◽  
First Time

The influence of external dielectric environments is well understood for 2D semiconductor materials but is overlooked for colloidally-grown II-VI nanoplatelets (NPLs). In this work, we synthesize MX (M=Cd, Hg; X= Se, Te) NPLs of varying thicknesses, and apply a modified Elliott model to fit excitonic absorption features and report exciton binding energies for cadmium telluride and mercury chalcogenides for the first time. Our observations indicate that the exciton binding energy is modulated by the dielectric screening of semiconductor material by the external ligand environment. Furthermore, NPL binding energies show a dependence on the number of monolayers consistent with relative effect of internal vs. external dielectric. To describe this, we derive an analytical electrostatic model, reinforcing the hypothesis that the external environment increases the exciton binding energy relative to the bulk—due to the distortion of the Coulombic potential across the NPL surface. We further confirm this effect by decreasing and recovering the exciton binding energy of HgTe NPLs through washing in polarizable solvents. Our results illustrate that NPLs are colloidal analogues of Van der Waals 2D semiconductors and point to surface modification as an approach to control photophysics and device properties.

scholarly journals Configuration space method for calculating binding energies of exciton complexes in quasi-1D/2D semiconductors

2016 ◽  
Vol 30 (24) ◽  
pp. 1630006 ◽  
Author(s):  
I. V. Bondarev
Keyword(s):  
Binding Energy ◽  
Quantum Wells ◽  
Configuration Space ◽  
Binding Energies ◽  
Electron Hole ◽  
Coupled Quantum Wells ◽  
2D Semiconductors ◽  
Crossover Behavior ◽  
Confined Structures ◽  
Space Method

A configuration space method is developed for binding energy calculations of the lowest energy exciton complexes (trion, biexciton) in spatially confined quasi-1D semiconductor nanostructures such as nanowires and nanotubes. Quite generally, trions are shown to have greater binding energy in strongly confined structures with small reduced electron–hole masses. Biexcitons have greater binding energy in less confined structures with large reduced electron–hole masses. This results in a universal crossover behavior, whereby trions become less stable than biexcitons as the transverse size of the quasi-1D nanostructure increases. The method is also capable of evaluating binding energies for electron–hole complexes in quasi-2D semiconductors such as coupled quantum wells and bilayer van der Walls bound heterostructures with advanced optoelectronic properties.

scholarly journals A new view on the origin of zero-bias anomalies of Co atoms atop noble metal surfaces

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Juba Bouaziz ◽  
Filipe Souza Mendes Guimarães ◽  
Samir Lounis
Keyword(s):  
Density Functional ◽  
Degrees Of Freedom ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Many Body ◽  
Magnetic Anisotropy Energy ◽  
Zero Bias ◽  
Relativistic Time ◽  
Wide Range ◽  
Spin Excitations

AbstractMany-body phenomena are paramount in physics. In condensed matter, their hallmark is considerable on a wide range of material characteristics spanning electronic, magnetic, thermodynamic and transport properties. They potentially imprint non-trivial signatures in spectroscopic measurements, such as those assigned to Kondo, excitonic and polaronic features, whose emergence depends on the involved degrees of freedom. Here, we address systematically zero-bias anomalies detected by scanning tunneling spectroscopy on Co atoms deposited on Cu, Ag and Au(111) substrates, which remarkably are almost identical to those obtained from first-principles. These features originate from gaped spin-excitations induced by a finite magnetic anisotropy energy, in contrast to the usual widespread interpretation relating them to Kondo resonances. Resting on relativistic time-dependent density functional and many-body perturbation theories, we furthermore unveil a new many-body feature, the spinaron, resulting from the interaction of electrons and spin-excitations localizing electronic states in a well defined energy.

Spatially resolved scanning tunneling spectroscopy of single-layer steps on Si(100) surfaces

2016 ◽  
Vol 94 (12) ◽  
Author(s):  
Xiqiao Wang ◽  
Pradeep Namboodiri ◽  
Kai Li ◽  
Xiao Deng ◽  
Richard Silver
Keyword(s):  
Single Layer ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Spatially Resolved

scholarly journals Assessment of density functional methods for exciton binding energies and related optoelectronic properties

RSC Advances ◽  
2015 ◽  
Vol 5 (123) ◽  
pp. 101370-101376 ◽  
Author(s):  
Jui-Che Lee ◽  
Jeng-Da Chai ◽  
Shiang-Tai Lin
Keyword(s):  
Binding Energy ◽  
Density Functional ◽  
Mean Absolute Error ◽  
Absolute Error ◽  
Binding Energies ◽  
Optoelectronic Properties ◽  
Exciton Binding Energy ◽  
Dft Methods ◽  
Density Functional Methods ◽  
Functional Methods

Mean absolute error (MAE) in exciton binding energy (Eb) from 9 DFT methods against benchmark CCSD and EOM-CCSD.

A Molecular Full-Potential LMTO Calculation for Copper Clusters

1997 ◽  
Vol 11 (05) ◽  
pp. 161-169 ◽  
Author(s):  
Radhika Prosad Datta ◽  
Amitava Banerjea ◽  
Abhijit Mookerjee ◽  
A. K. Bhattacharyya
Keyword(s):  
Simulated Annealing ◽  
Binding Energy ◽  
Electronic Properties ◽  
Density Of States ◽  
Cluster Size ◽  
Binding Energies ◽  
Full Potential ◽  
Copper Clusters ◽  
Total Energies ◽  
Homo Lumo

We study the electronic properties of small (10–20 atoms) copper clusters using the newly-developed molecular full-potential linearized muffin-tin orbital two-centre-fit (TCF) method of Methfessel and van Schilfgaarde. The geometric structures of the clusters had earlier been determined by us through simulated annealing using the Equivalent Crystal Theory to compute total energies. We report the variation of the binding energy, as obtained from the TCF calculations, with cluster size and compare these to the binding energies determined, for the same structures, from the ECT. We also show the variation of the HOMO-LUMO gap with cluster size, and the pseudo-density of states for select cluster sizes.

DYNAMICS OF DEEPLY BOUND ${\bar K}$ STATES

2007 ◽  
Vol 22 (02n03) ◽  
pp. 633-636 ◽  
Author(s):  
JIŘI MAREŠ ◽  
ELIAHU FRIEDMAN ◽  
AVRAHAM GAL
Keyword(s):  
Binding Energy ◽  
Mean Field ◽  
Binding Energies ◽  
Light Nuclei ◽  
Nucleus Interaction ◽  
Core Nucleus ◽  
Relativistic Mean Field ◽  
The Core ◽  
Wide Range ◽  
Rmf Model

Dynamical effects for [Formula: see text] deeply bound nuclear states are explored within a relativistic mean field (RMF) model. Varying the strength of [Formula: see text] - nucleus interaction, we cover a wide range of binding energies in order to evaluate the corresponding widths. A lower limit [Formula: see text] is placed on the width expected for binding energy in the range of [Formula: see text]. Substantial polarization of the core nucleus is found in light nuclei. We discuss the results of the FINUDA experiment at DAΦNE which presented evidence for deeply bound K- pp states in Li and 12 C .

Luminescence Studies of MBE Grown SI/SIGE Quantum Wells

1993 ◽  
Vol 298 ◽  
Author(s):  
M. Gail ◽  
J. Brunner ◽  
U. Menczigar ◽  
A. Zrenner ◽  
G. Abstreiter
Keyword(s):  
Binding Energy ◽  
Quantum Well ◽  
Quantum Wells ◽  
Elevated Temperatures ◽  
Variational Calculation ◽  
Exciton Binding Energy ◽  
Quantum Well Structures ◽  
Mass Approximation ◽  
Wide Range ◽  
Good Agreement

AbstractWe report on detailed luminescence studies of MBE grown Si/Si1-xGex quantum well structures. Both well width and composition is varied over a wide range. Bandgap photoluminescence is observed for all samples grown at elevated temperatures. The measured bandgap energies are in good agreement with subband calculations based on effective mass approximation and taking into account the segregation of Ge atoms during growth. Diffusion is found to limit quantum well (QW) growth with Ge-contents above 35% at high temperatures. The photoluminescence signals are detected up to about 100K and can be attributed to interband transitions of free excitons. We also present investigations of the exciton binding energy as a function of well width and composition. The observed shift of the exciton binding energy is compared with results of a variational calculation. A distinct onset in photocurrent and electroluminescence up to 200 K are observed in quantum well diodes.

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