Charge-lattice Interaction Research Articles

Strong Charge Transfer at 2H-1T Phase Boundary of MoS2 for Superb High-Performance Energy Storage.

Transition metal dichalcogenides exhibit several different phases (e.g., semiconducting 2H, metallic 1T, 1T') arising from the collective and sluggish atomic displacements rooted in the charge-lattice interaction. The coexistence of multiphase in a single sheet enables ubiquitous heterophase and inhomogeneous charge distribution. Herein, by combining the first-principles calculations and experimental investigations, a strong charge transfer ability at the heterophase boundary of molybdenum disulfide (MoS2 ) assembled together with graphene is reported. By modulating the phase composition in MoS2 , the performance of the nanohybrid for energy storage can be modulated, whereby remarkable gravimetric and volumetric capacitances of 272 F g-1 and 685 F cm-3 are demonstrated. As a proof of concept for energy application, a flexible solid-state asymmetric supercapacitor is constructed with the MoS2 -graphene heterolayers, which shows superb energy and power densities (46.3 mWh cm-3 and 3.013 W cm-3 , respectively). The present work demonstrates a new pathway for efficient charge flow and application in energy storage by engineering the phase boundary and interface in 2D materials of transition metal dichalcogenides.

Habituation based synaptic plasticity and organismic learning in a quantum perovskite

A central characteristic of living beings is the ability to learn from and respond to their environment leading to habit formation and decision making. This behavior, known as habituation, is universal among all forms of life with a central nervous system, and is also observed in single-cell organisms that do not possess a brain. Here, we report the discovery of habituation-based plasticity utilizing a perovskite quantum system by dynamical modulation of electron localization. Microscopic mechanisms and pathways that enable this organismic collective charge-lattice interaction are elucidated by first-principles theory, synchrotron investigations, ab initio molecular dynamics simulations, and in situ environmental breathing studies. We implement a learning algorithm inspired by the conductance relaxation behavior of perovskites that naturally incorporates habituation, and demonstrate learning to forget: a key feature of animal and human brains. Incorporating this elementary skill in learning boosts the capability of neural computing in a sequential, dynamic environment.

Optical properties of antiferroelectric Cs2Nb4O11: Absorption spectra and first-principles calculations

We report a joint experimental and theoretical investigation of the optical properties of Cs2Nb4O11. In room temperature optical absorption spectra, we found a direct gap about 3.55 ± 0.05 eV and charge transfer excitations at about 4.96 and 6.08 eV, which are in good agreement with the first-principles calculations. Upon passing through the 165 °C antiferroelectric to paraelectric phase transition, the peak energies of two charge transfer bands display almost no temperature dependence, yet they become even broader and exhibit enhanced oscillator strength. We infer this intriguing behavior as the manifestation of Nb cation distortions due to the charge-lattice interaction.

Evidences of the Charge–Lattice Interaction in Undoped Cuprates

The anomalous temperature dependence of the angle resolved photoemission spectra (ARPES) in undoped cuprates is investigated by using a self-consistent approach within the t-J-Holstein model. The cooperative interplay of coupling of the hole to magnetic fluctuations and strong electron–phonon interaction turns out crucial to explain the experimental data. The model is extended to take into account the longer-range hoppings t′ and t′′. The effect is a large anisotropy of the electron–phonon interaction (EPI) leading to a completely different influence of EPI on the nodal and antinodal points in agreement with the experiments.

The Crucial Interplay Between Spin, Charge and Lattice in Organic Superconducting Charge Transfer Salts

Even though superconductivity in organic charge transfer salts (CTS) is unconventional since evidence for a d-wave order parameter is seen , lattice effect play a crucial role, because isotope effects have been observed as well as substantial influences of the insulating buffer layers on the material properties. Consequently, models for CTS should not only take strong correlations into account but also consider spin, charge lattice interaction effects together with a-axis coupling arising from the anionic buffer layers. Here, we propose a novel model, where these latter effects are incorporated and various experimental findings consistently explained.

Anomalous sound velocity behavior of La 1−XCa XMnO 3 ( X∼0.48) in applied field

The sound velocity v s( T) has been investigated for La 1− X Ca X MnO 3 (0.46⩽ X⩽0.50) in applied fields up to μ 0 H = 5 T . The characteristic v s( T) softening and the subsequent hardening are observed below the ferromagnetic transition temperature T c. The gradual v s( T) softening above the charge-order (CO) transition temperature T CO and the v s( T) hardening just below T CO are also observable. The v s( T) softening above T CO is at first enhanced and then reduced with increasing applied field. These results can be understood on the basis of the enhanced spin–lattice and charge–lattice interaction.

Dc and ac electrical transport in assete systems

The electrical charge transport in AsSeTe glasses has been investigated by correlating the dc and ac conductivity measurements performed at different temperatures. It was possible to separate the bulk properties from those at the insulator-metal interface. The deduced hopping parameters favour a single-channel hopping model of charges (strongly localised through finite charge-lattice interaction) hopping in a narrow band of states. The importance of the knowledge of the space distribution of the charge in the contact region for the correct interpretation of the experimental results is stressed.

D.C. and A.C. Electrical transport in assete system

The electrical charge transport in AsSexTe1 − x glasses have been investigated by correlating the d.c. and the a.c. conductivity measurements performed at different temperatures. It was possible to separate the bulk properties from those at the insulator-metal interface. The deduced hopping parameters favour a single channel hopping model of charges (strongly localised through finite charge-lattice interaction) hopping in a narrow band of states. The importance of the knowledge of the space distribution of the charge in the contact region for the correct interpretaton of the experimental results is stressed.

The absence of exchange or motional narrowing of E.S.R. absorption lines, the spatial extend of the localised paramagnetic centres and the role played by the charge-lattice interaction in amorphous semiconductors without and with hydrogen

The absence of any sizable exchange or motional narrowing of the electron spin resonance absorption lines for samples with high concentration of homogeneously distributed spins indicate that the paramagnetic centres in amorphous Ge and Si are severly localised. An upper limit to the decay parameter α of the spatial extend of the wavefunction describing the “free” spin in shown to be less than α −1 < 2.5 A ̊ . If different charge states of the paramagnetic centres are assumed to exist within the gap of amorphous Si and Ge, large charge-lattice interaction is therefore required in order to offset the Coulomb repulsion. A possible model for the electron states in the gap of hydrogenated amorphous silicon (doped or undoped) is proposed which takes this into account explicitly.