scholarly journals Absence of a charge diffusion pole at finite energies in an exactly solvable interacting flat-band model in d dimensions

2018 ◽  
Vol 97 (19) ◽  
Author(s):  
Philip W. Phillips ◽  
Chandan Setty ◽  
Shuyi Zhang
Keyword(s):  
Flat Band ◽  
Band Model ◽  
Exactly Solvable ◽  
A Charge ◽  
Diffusion Pole

scholarly journals Extremely flat band in bilayer graphene

2018 ◽  
Vol 4 (11) ◽  
pp. eaau0059 ◽  
Author(s):  
D. Marchenko ◽  
D. V. Evtushinsky ◽  
E. Golias ◽  
A. Varykhalov ◽  
Th. Seyller ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Bilayer Graphene ◽  
Flat Band ◽  
Honeycomb Lattice ◽  
Band Model ◽  
Two Dimensional ◽  
Band Formation ◽  
Constant Energy ◽  
Mexican Hat ◽  
Band Dispersion

We propose a novel mechanism of flat band formation based on the relative biasing of only one sublattice against other sublattices in a honeycomb lattice bilayer. The mechanism allows modification of the band dispersion from parabolic to “Mexican hat”–like through the formation of a flattened band. The mechanism is well applicable for bilayer graphene—both doped and undoped. By angle-resolved photoemission from bilayer graphene on SiC, we demonstrate the possibility of realizing this extremely flattened band (< 2-meV dispersion), which extends two-dimensionally in a k-space area around the K¯ point and results in a disk-like constant energy cut. We argue that our two-dimensional flat band model and the experimental results have the potential to contribute to achieving superconductivity of graphene- or graphite-based systems at elevated temperatures.

scholarly journals Self-consistent treatment of v-groove quantum wire band structure in no parabolic approximation

2004 ◽  
Vol 1 (3) ◽  
pp. 69-77 ◽  
Author(s):  
Jasna Crnjanski ◽  
Dejan Gvozdic
Keyword(s):  
Band Structure ◽  
Quantum Wire ◽  
The Self ◽  
Flat Band ◽  
Band Model ◽  
Parabolic Approximation ◽  
Self Consistent ◽  
Band Absorption ◽  
Consistent Treatment ◽  
Self Consistency

The self-consistent no parabolic calculation of a V-groove-quantum-wire (VQWR) band structure is presented. A comparison with the parabolic flat-band model of VQWR shows that both, the self-consistency and the nonparabolicity shift sub band edges, in some cases even in the opposite directions. These shifts indicate that for an accurate description of inter sub band absorption, both effects have to be taken into the account.

scholarly journals Solitons in one-dimensional three-band model with a central flat band

2013 ◽  
Vol 88 (24) ◽  
Author(s):  
Gyungchoon Go ◽  
Kyeong Tae Kang ◽  
Jung Hoon Han
Keyword(s):  
Flat Band ◽  
Band Model ◽  
One Dimensional

scholarly journals Probing the nature of an emergent insulator in ionic gated monolayer transition metal dichalcogenides

2020 ◽  
Author(s):  
Maosen Qin ◽  
Dongdong Ding ◽  
Siheng Li ◽  
Xiangyan Han ◽  
Ruirui Niu ◽  
...  
Keyword(s):  
Transition Metal ◽  
Density Wave ◽  
Transition Metal Dichalcogenides ◽  
Flat Band ◽  
Emergent Phenomena ◽  
Evolutionary Changes ◽  
Metal Dichalcogenides ◽  
Half Filling ◽  
A Charge ◽  
Enhanced Superconductivity

Abstract Electronic correlation in a flat band has been a longstanding interest because of emergent phenomena such as Mott insulator and superconductivity. Besides recent Moiré superlattice, transition metal dichalcogenides (TMDs) may directly, e.g. by forming a charge density wave in 1T-TaS2, reconstruct a narrow band that exhibits a correlated insulator. Here we report an emergent insulator in electron doped monolayer WSe2, a prototypical TMDs with direct bandgaps. By detailed mapping a cascade of phases “band insulator-superconductor-emergent insulator-metal”, we can identify, besides the superconducting dome, a narrow miniband split from the conduction band, half filling of which coincides with the insulating state. The correlation picture is supported by a density wave that possesses an isolated flat band. Finally, through evolutionary changes within the same class of materials, multivalley population is suggested to account for enhanced superconductivity and the insulator. Our finding provides new opportunities to explore correlated physics within traditionally non-correlated materials.

Two-Photon Absorption of Biexcitons for a Truncated Potential

1995 ◽  
Vol 413 ◽  
Author(s):  
F. B. Gallagher ◽  
F. C. Spano
Keyword(s):  
Nearest Neighbor ◽  
Tight Binding ◽  
Photon Absorption ◽  
Basis Sets ◽  
Band Model ◽  
Two Photon Absorption ◽  
Coulombic Interactions ◽  
Two Photon ◽  
A Charge ◽  
Two Parameters

ABSTRACTA tight binding, one dimensional, two-band model is used to investigate the formation and nonlinear optical properties of biexcitons in conjugated polymers. The full single and double electron-hole pair basis sets are explicitly considered for a Hamiltonian which includes an electron and hole transfer parameter (t) along with a truncated potential with only on-site (V0 ) and nearest neighbor (V1) Coulombic interactions. The biexciton phase space is determined to be a function of only two parameters α and βwhere α ≅V1/V0 and β ≅t/V0. Due to the truncated potential only a single biexciton eigenstate is formed in the region limited by 0.64 < α≤ 1 and 0 ≤ β< 0.33. The two-photon absorption spectra in the range 0 < hω < δ, where δ is the one photon gap, are found to contain at most two types of peaks: one arising from a biexciton and another due to a charge-transfer, single-exciton. The polymer limit is obtained and used to investigate polymers with large alternation such as polysilane.

ON THE ORIGIN OF d-WAVE PAIR FUNCTIONS IN HIGH-Tc SUPERCONDUCTIVITY

2006 ◽  
Vol 20 (23) ◽  
pp. 3279-3305
Author(s):  
DANIEL C. MATTIS
Keyword(s):  
Band Model ◽  
Checkerboard Pattern ◽  
Coupling Constant ◽  
S Wave ◽  
High Tc ◽  
Lumped Parameter ◽  
Intimate Relation ◽  
A Charge ◽  
Fine Tune ◽  
D Wave

We argue that the usual Hubbard's model produces only s-wave pairing functions and, even then, only at unphysically large values of the lumped parameter J≡4t2/U. It follows that a reliable theory of high-Tc superconductivity has to include additional features if it is to reproduce the d-wave gap. We test the effects of an alternating potential caused by a charge stripe, on the ground state of the Hubbard model in strong-coupling. If we "fine tune" we do find the d-waves. However, a better-formulated version of a three-band model yields a sturdier theory of pair formation in high-Tc superconductivity. The coupling constant g1=t2/V factors out, hence it serves only to establish the unit of energy; the underlying Hamiltonian is universal. We outline the principal properties of this model, including the intimate relation between charge-density stripes and the d-wave pair function, its rejection of 45° stripes (checkerboard pattern), and other concerns.

scholarly journals High Pressure Deuterium Passivation of Charge Trapping Layer for Nonvolatile Memory Applications

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1316
Author(s):  
Jae-Young Sung ◽  
Jun-Kyo Jeong ◽  
Woon-San Ko ◽  
Jun-Ho Byun ◽  
Hi-Deok Lee ◽  
...  
Keyword(s):  
High Pressure ◽  
Nonvolatile Memory ◽  
Charge Trapping ◽  
Memory Device ◽  
Trap Density ◽  
Flat Band ◽  
Data Retention ◽  
Retention Model ◽  
A Charge ◽  
Memory Applications

In this study, the deuterium passivation effect of silicon nitride (Si3N4) on data retention characteristics is investigated in a Metal-Nitride-Oxide-Silicon (MNOS) memory device. To focus on trap passivation in Si3N4 as a charge trapping layer, deuterium (D2) high pressure annealing (HPA) was applied after Si3N4 deposition. Flat band voltage shifts (ΔVFB) in data retention mode were compared by CV measurement after D2 HPA, which shows that the memory window decreases but charge loss in retention mode after program is suppressed. Trap energy distribution based on thermal activated retention model is extracted to compare the trap density of Si3N4. D2 HPA reduces the amount of trap densities in the band gap range of 1.06–1.18 eV. SIMS profiles are used to analyze the D2 profile in Si3N4. The results show that deuterium diffuses into the Si3N4 and exists up to the Si3N4-SiO2 interface region during post-annealing process, which seems to lower the trap density and improve the memory reliability.

Amorphous Silicon Based TFT and MIS Nonvolatile Memories

2007 ◽  
Vol 989 ◽  
Author(s):  
Yue Kuo ◽  
Helinda Nominanda
Keyword(s):  
Amorphous Silicon ◽  
Gate Dielectric ◽  
Low Cost ◽  
Flat Band ◽  
Nonvolatile Memories ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
Voltage Hysteresis ◽  
A Charge ◽  
Silicon Based

AbstractThe amorphous silicon (a-Si:H) TFT and MIS capacitor, which include an a-Si:H layer embedded in the silicon nitride gate dielectric layer, have been prepared and characterized for memory functions. Large shifts of the threshold voltage and flat band voltage were detected in the current-voltage and capacitance-voltage hysteresis measurements. The embedded a-Si:H film functioned as a charge retention medium that stores and releases injected carriers. The devices memory capacity varied with the thickness of the embedded a-Si:H layer and the sweep voltage. These low-cost memory devices can be used in many low-temperature prepared circuits.

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