Adiabatic Method Research Articles

Theoretical Exploration of Carrier Dynamics in Amorphous Pyrene-Fluorene Derivative Organic Semiconductors.

In this report, a series of amorphous organic optoelectronic pyrene–fluorene derivative materials (BP1, BP2, PFP1, PFP2, OP1, OP2) were systematically investigated through a theoretical method. Their molecular structures are different due to the difference of substitution groups at C9 of the fluorene core, which include electron-rich pyrene group (PFP1 and PFP2), relatively neutral phenyl group (BP1 and BP2), and electron-withdrawing oxadiazole group (OP1 and OP2). In the beginning, through the physical model analysis, this report proposes that the concept of p-type or n-type is not flawless because there is no real doping process in these molecular organic semiconductors. To prove such a concept, the Marcus theory and first-principles were employed to calculate the intrinsic transfer mobility of these materials. Not as the common method used for the single crystal, in this report, a series of disorderly designed lattice cells were constructed to represent the disordered distribution of the amorphous pyrenyl–fluorene derivatives. Then, the reorganization energy of materials was calculated by the adiabatic potential energy surface method. The transfer integral of dimers was calculated in possible hopping pathways near the central molecule. Research results show that the six pyrene–fluorene materials all possess intrinsic bipolar transfer characteristics. In addition, it is also showed that the electron-rich group is not necessary to improve hole transfer, and that the electron-withdrawing group is also not necessary to improve electron transfer.

Low-temperature thermodynamic properties of dimeric tris(2,2,6,6-tetramethyl-3,5-heptanedionato) europium

A sample of dimeric tris(2,2,6,6-tetramethyl-3,5-heptanedionato) europium ([Eu(C11H19O2)3]2 or dipivaloylmethanate europium) was synthesized. Chemical analysis, elemental analysis and X-ray crystallography were used to characterize composition and structure of the complex. Low-temperature heat capacity of the sample was measured by adiabatic method in a temperature range from 8.63 K to 312.90 K. The Debye temperature at 0 K was calculated. Thermodynamic functions (entropy, enthalpy, reduced Gibbs energy) in a range (0–312) K have been calculated using the obtained experimental heat capacity data. An anomaly in the functional behaviour of heat capacity was detected in a temperature range from 250 K to 270 K, with a maximum at Tc = (262.36 ± 0.01) K. A reversible colour change (thermochromism) of europium dipivaloylmethanate crystals upon cooling below 245 K was detected. Anomalous contributions to entropy and enthalpy have been revealed. The nature of the effects detected is discussed.

Adiabatic projection method with Euclidean time subspace projection

Euclidean time projection is a powerful tool that uses exponential decay to extract the low-energy information of quantum systems. The adiabatic projection method, which is based on Euclidean time projection, is a procedure for studying scattering and reactions on the lattice. The method constructs the adiabatic Hamiltonian that gives the low-lying energies and wave functions of two-cluster systems. In this paper we seek the answer to the question whether an adiabatic Hamiltonian constructed in a smaller subspace of the two-cluster state space can still provide information on the low-lying spectrum and the corresponding wave functions. We present the results from our investigations on constructing the adiabatic Hamiltonian using Euclidean time projection and extracting details of the low-energy spectrum and wave functions by diagonalizing it. In our analyses we consider systems of fermion-fermion and fermion-dimer interacting via a zero-range attractive potential in one dimension, and fermion-fermion interacting via an attractive Gaussian potential in three dimensions. The results presented here provide a guide for improving the adiabatic projection method and for reducing the computational costs of large-scale calculations of \emph{ab initio} nuclear scattering and reactions using Monte Carlo methods.

Features of the Low-Temperature Heat Capacity of Er3 –xTmxAl5O12 Garnet Single Crystals

In this paper, we present the results of studies of the heat capacity of single-crystal garnets Er3 ‒ xTmxAl5O12 (x = 0, 1, 2, 3) in magnetic fields of up to 9 T and in the temperature range 1.9–220 K. The temperature dependences of the heat capacity are approximated using the sum of the contributions of Schottky anomalies associated with magnetic Er3+ and Tm3+ ions and the Debye and Einstein lattice contributions. Entropy and magnetic entropy are calculated using the heat capacity data. With an increase in the magnetic field, entropy is shown to decrease. This indicates the possibility of using the studied garnets in the adiabatic demagnetization method.

The Intriguing Case of the One‐Photon and Two‐Photon Absorption of a Prototypical Symmetric Squaraine: Comparison of TDDFT and Wave‐Function Methods

AbstractWe face the challenging description of the excited states responsible for one photon (OPA) and two photon (TPA) absorption in squaraine dyes, adopting both time‐dependent density functional theory and a large variety of post Hartree Fock methods, including coupled cluster and adiabatic diagrammatic construction methods (ADC, to the second and third order), symmetry adapted cluster configuration interaction (CI), CASSCF including second‐order perturbative corrections (PT2) with standard CASPT2 recipe and according to n‐electron valence PT2 (NEVPT2) approach, and an additional multireference CI with PT2 corrections (CI‐MRPT2). We selected a small prototypical symmetric squaraine dye for which these accurate computations are feasible and experimental data are available. We show that while all methods reasonably reproduce the OPA spectrum, an acceptable description and assignment of the states responsible for TPA is only possible through ADC(3) and multireference calculations, due to the strong involvement of double‐excitations. The nature of ground state and OPA and TPA states is investigated with a rigorous reading of the CASSCF wavefunctions in terms of localized molecular orbitals on the donor and acceptor fragments, showing that these states arise from a balance of many different contributions including biradical configurations, local excitations and charge‐transfer states where both side aromatic rings and the carbonyls of the squarylium moiety act as donors.

Low-temperature properties of BaWO4 based on experimental heat capacity in the range 5.7–304 K

The heat capacity of barium tungstate single crystal was measured by the adiabatic method in the range of 5.7–304 K. No anomalies in the heat capacity associated with the phase transition were found. The analysis of the functional behavior of heat capacity near zero revealed a low-frequency peak in the phonon density of states of BaWO4. An approach was proposed to allow quantitative description of the acoustic wing of the phonon density of states. The approximation of experimental data by an analytical expression was done, including the temperature region near 0 K. The Debye temperature at absolute zero has been obtained. The thermodynamic functions were calculated: entropy, enthalpy increment and Gibbs free energy.

Low-temperature thermodynamic properties of Al(C5HF6O2)3

The heat capacity for tris-hexafluoroacetylacetonate of aluminium (Al(C5HF6O2)3 or tris(1,1,1,5,5,5-hexafluoro-2,4-pentanedionate) aluminium (III)) within a temperature range (9.83–299.76) K has been measured by the adiabatic method. The functional behaviour of sample’s heat capacity was analysed. No phase transition-related anomalies in the heat capacity behaviour were found. Crystal lattice anisotropy of a studied complex was evaluated. The Debye temperature at 0 K was calculated. The obtained data were used to calculate smoothed values of heat capacity, entropy, enthalpy, and reduced Gibbs energy in a temperature range of 0 K to 300 K. They have the following values at 298.15 K: C°p,m = (608.3 ± 1.0) J K−1 mol−1, Δ0298.15S°m = (786.5 ± 2.1) J K−1 mol−1, Δ0298.15H°m = (106.91 ± 0.20) kJ mol−1, Φ°m = (428.0 ± 1.4) J K−1 mol−1. The value of the absolute entropy were used to calculate the entropy of formation of Al(C5HF6O2)3 (cr) at T = 298.15 K.

Breaking the quantum adiabatic speed limit by jumping along geodesics.

Quantum adiabatic evolutions find a broad range of applications in quantum physics and quantum technologies. The traditional form of the quantum adiabatic theorem limits the speed of adiabatic evolution by the minimum energy gaps of the system Hamiltonian. Here, we experimentally show using a nitrogen-vacancy center in diamond that, even in the presence of vanishing energy gaps, quantum adiabatic evolution is possible. This verifies a recently derived necessary and sufficient quantum adiabatic theorem and offers paths to overcome the conventionally assumed constraints on adiabatic methods. By fast modulation of dynamic phases, we demonstrate near-unit-fidelity quantum adiabatic processes in finite times. These results challenge traditional views and provide deeper understanding on quantum adiabatic processes, as well as promising strategies for the control of quantum systems.

A Mutual Capacitance Touch Readout IC With 64% Reduced-Power Adiabatic Driving Over Heavily Coupled Touch Screen

This paper presents a touch sensing analog front end (AFE) for capacitive touch-screen integrated into an ultra-thin display. Reduced distance between the touch screen and display causes large capacitive coupling, resulting in increased parasitic capacitance and reduced touch sensitivity. Display noise interference is worse due to the large coupling capacitance. Hence, it is a challenge to design an AFE capable of accurate and energy efficient sensing of a touch input in the integrated touch-screen panel. An adiabatic multi-driving method based on charge recycling is proposed to provide power-efficient stimulation of the touch-screen panel. Furthermore, in order to cancel out the display noise interference through the large parasitic capacitance, a fully differential touch sensing module is incorporated in the AFE. A correlated noise sampling (NS) is employed in the decoder stage for the multi-driving demodulation process. To further improve power efficiency, the sensing module is multiplexed in four ways while achieving an optimal conversion time per sample. The proposed AFE was implemented in a 180-nm CMOS process. The fabricated AFE shows 57.0-dB signal-to-noise ratio (SNR) at 120 fps while consuming 17.8 mW. Compared with power consumption of 19.9 mW expected with a conventional signal generation, the proposed adiabatic signal generator dissipates only 7.1 mW, exhibiting a power reduction of 64% due to the adiabatic driving method.

Combined Quantum Trajectory Mean‐Field and Molecular Mechanical (QTMF/MM) Nonadiabatic Dynamics Simulations on the Photoinduced Ring‐Opening Reaction of 2(5H)‐Thiophenone

AbstractIn the present work, the direct ab initio quantum trajectory mean‐field and molecular mechanical (QTMF/MM) nonadiabatic dynamics approach has been numerically implemented and used to simulate the photo‐induced ring‐opening process of 2(5H)‐thiophenone in CH3CN solution. Meanwhile, the subsequent processes in the S0 state have been simulated employing a quantum mechanics/molecular mechanics (QM/MM) adiabatic dynamics method that is derived from the direct ab initio QTMF/MM nonadiabatic dynamics approach. Upon irradiation at 267 nm, 2(5H)‐thiophenone is initially populated to its bright 1ππ* state. Subsequently, the ring‐opening reaction is predicted to be an ultrafast process with a time constant of about 228 fs. As a result, the ring‐opening reaction proceeds mainly along the diabatic S2(1ππ*) pathway and the solute‐solvent interaction has little influence on this initial process. Meanwhile, the 1ππ*→1πσ* transition takes place with little probability via the 1πσ*/1ππ* conical intersection and the 1πσ* excited state plays a minor role in the ring‐opening reaction, which is quite different from those reported for many heterocyclic molecules. Reformation of the parent molecule in the S0 state is determined to have a quantum yield of 33.9 % within the simulated period of 3.5 ps, which is considerably underestimated in comparison with a value of ∼60.0 % inferred experimentally. Thioaldehyde‐ketene was experimentally inferred as a product, which is confirmed by the simulations reported herein.

Dual infrared limits of 6d [formula omitted] theory

Compactifying type AN−1 6d N=(2,0) supersymmetric CFT on a product manifold M4×Σ2=M3×S˜1×S1×I either over S1 or over S˜1 leads to maximally supersymmetric 5d gauge theories on M4×I or on M3×Σ2, respectively. Choosing the radii of S1 and S˜1 inversely proportional to each other, these 5d gauge theories are dual to one another since their coupling constants e2 and e˜2 are proportional to those radii respectively. We consider their non-Abelian but non-supersymmetric extensions, i.e. SU(N) Yang–Mills theories on M4×I and on M3×Σ2, where M4⊃M3=Rt×Tp2 with time t and a punctured 2-torus, and I⊂Σ2 is an interval. In the first case, shrinking I to a point reduces to Yang–Mills theory or to the Skyrme model on M4, depending on the method chosen for the low-energy reduction. In the second case, scaling down the metric on M3 and employing the adiabatic method, we derive in the infrared limit a non-linear SU(N) sigma model with a baby-Skyrme-type term on Σ2, which can be reduced further to AN−1 Toda theory.

Determination of thermal expansion coefficients in shocked compounds

Differences in volumes of solid compounds compressed by the static (cold) and shock-wave (adiabatic) methods are caused by the enhanced temperatures in the last case that allows the determination of thermal expansion coefficients of materials under pressures. Thermodynamic consideration of the thermal behavior in compressed solids shows that, usually, positive ▵V under ambient conditions implies negative ▵V under high pressure, and vice versa. The changing sign of ▵V is not due to structural transformations.

Heat capacity and thermal expansion of yttrium tantalate

The isobaric heat capacities of two monoclinic (M' and M) modifications of yttrium orthotantalate at temperatures 5–1300 K have been measured by the adiabatic and differential scanning calorimetry methods. It has been demonstrated that the difference in structure between the crystal lattices of M' and M has small effect in the heat capacity, and the difference between the heat capacities of these phases Cp(M)-Cp(M') is small, always positive, and increases in the range of the lowest temperatures. The unit cell parameters of M-YTaO4 have been determined as a function of temperature in the range 300–1173 K.

Accelerating adiabatic protocols for entangling two qubits in circuit QED

We introduce a method to speed up adiabatic protocols for creating entanglement between two qubits dispersively coupled to a transmission line, while keeping fidelities high and maintaining robustness to control errors. The method takes genuinely adiabatic sweeps, ranging from a simple Landau-Zener drive to boundary cancellation methods and local adiabatic drivings, and adds fast oscillations to speed up the protocol while canceling unwanted transitions. We compare our protocol with existing adiabatic methods in a state-of-the-art parameter range and show substantial gains. Numerical simulations emphasize that this strategy is efficient also beyond the rotating-wave approximation and that the method is robust against random static biases in the control parameters and with respect to damping and decoherence effects.

Distribution of the functional groups in various coals with different spontaneous propensity

ABSTRACTThe distribution of oxygen-containing functional groups, aromatic hydrocarbons, and aliphatic groups in coal with different spontaneous combustion propensity were studied. Adiabatic method was used to determine the spontaneous combustion propensity of six different coal samples. FTIR was used to collect the spectrum of the coal, and the peak areas of the functional groups were analyzed. The proportion of C = C, CH3/CH2, OH, C = O, COOH, C-O, and C-O-O obtained based on the peak areas was calculated, and the spontaneous combustion propensity was characterized by the distribution of the functional groups. It was found that there is a good corresponding relationship between the content of aromatic functional groups and oxygen-containing functional groups with the self-heating time of the coal samples. The coal with shorter self-heating time has less aromatic groups and more oxygen-containing functional groups. With the increase of the spontaneous combustion propensity of coal, there are less aliphatic hydrocarbons functional groups generally. But among different coal samples, the contents of aliphatic hydrocarbons functional groups differ not great.

Running couplings from adiabatic regularization

We extend the adiabatic regularization method by introducing an arbitrary mass scale μ in the construction of the subtraction terms. This allows us to obtain, in a very robust way, the running of the coupling constants by demanding μ-invariance of the effective semiclassical (Maxwell-Einstein) equations. In particular, we get the running of the electric charge of perturbative quantum electrodynamics. Furthermore, the method brings about a renormalization of the cosmological constant and the Newtonian gravitational constant. The running obtained for these dimensionful coupling constants has new relevant (non-logarithmic) contributions, not predicted by dimensional regularization.

Renormalized stress tensor of a quantized massless scalar field in warped cosmological braneworld background

Energy momentum tensor of a conformally coupled quantum scalar field in five dimensional warped cosmological spacetimes is studied. We look at situations where the four dimensional part represents a cosmological thick brane and the scale of the extra dimension is time dependent. Renormalization of the components of the energy momentum tensor is achieved using adiabatic regularization method. The resulting energy and pressure densities explicitly show the effects of warping and the dynamic extra dimension on the created matter. We discussed how the created matter may accumulate to form thick branes along the extra dimension.

DFT/TD-DFT investigation on the UV–vis absorption and phosphorescence spectra of platinum(II) and palladium(II) complexes with Schiff-base ligands

Abstract In this work, we studied the structural and optical properties of the three complexes: 2,3-bis[(4-diethylamino-2-hydroxybenzylidene)-amino]but-2-enedinitrile (Pd-1), 2,3-bis[(4 diethylamino-2-hydroxybenzylidene)-amino]but-2-enedinitrile (Pt-1), and 2,3-bis(3,3,9,9-tetramethyl-2-hydroxyjulolidine)but-2-enedinitrile (Pd-2) using DFT and TD-DFT methods. The electronic and geometrical structures of the ground state (S0) and the first triplet excited state (T1) have been analyzed and compared. Observed absorption bands were assigned according to NTO analyzes, the agreement with the experience is good. LLCT character dominates the low-lying singlet excited states. Phosphorescence wavelengths of the studied complexes were calculated vertically and adiabatically. The adiabatic methods are more accurate. Phosphorescence spectra were simulated taking into account the vibronic coupling using FC/AH and FC/AS approaches. The normal modes involved in phosphorescence maxima were identified, analyzed and assigned to the observed emission maxima.

Temporal Coherence for Sound Transmission Through Fluctuating Deep Water with Adiabatic Perturbed Modes

Adiabatic approximation (AP) combined with perturbation theory gives a fast normal-mode solution of temporal coherence for sound field in a two-dimensional deep water with time-varying random internal waves. Internal waves induced mode changes are deduced using the first-order perturbation theory [C. T. Tindle, L. M. O’Driscoll and C. J. Higham, Coupled mode perturbation theory of range dependence, J. Acoust. Soc. Am. 108(1) (2000) 76–83]. And mode perturbations in amplitude are neglected by the adiabatic method with wavenumber perturbations in phase merely considered. The AP expression of temporal coherence function is theoretically identical to the adiabatic transport equation theory [J. A. Colosi, T. K. Chandrayadula, A. G. Voronovich and V. E. Ostashev, Coupled mode transport theory for sound transmission through an ocean with random sound speed perturbations: Coherence in deep water environments, J. Acoust. Soc. Am. 134(4) (2013) 3119–3133]. Numerical results of the adiabatic temporal coherence function for several low frequencies and ranges up to 1000[Formula: see text]km are calculated. Then the coherence time scales obtained from the calculations are examined by a one-way coupled theory considering forward scattering [A. G. Voronovich, V. E. Ostashev and J. A. Colosi, Temporal coherence of acoustic signals in a fluctuating ocean, J. Acoust. Soc. Am. 129(6) (2011) 3590–3597]. Comparisons demonstrate that the range and frequency dependence of coherence time for both methods are quite close. And this shows good agreement with the well-known inverse frequency and inverse square root range laws. In addition, the internal wave energy dependence of coherence time is also studied.

Realization of the Kohn's Theorem in Ge/Si Quantum Dots with Hole Gas: Theory and Experiment.

This article discusses specific quantum transitions in a few-particle hole gas, localized in a strongly oblate lens-shaped quantum dot. Based on the adiabatic method, the possibility of realizing the generalized Kohn theorem in such a system is shown. The criteria for the implementation of this theorem in a lens-shaped quantum dot, fulfilled in the experiment, is presented. An analytical expression is obtained for the frequencies of resonant absorption of far-infrared radiation by a gas of heavy holes, which depends on the geometric parameters of the quantum dot. The results of experiments on far-infrared absorption in the arrays of p-doped Ge/Si quantum dots grown by molecular beam epitaxy (MBE) with gradually increasing average number of holes in dot are presented. Experimental results show that the Coulomb interaction between the holes does not affect the resonant frequency of the transitions. A good agreement between the theoretical and experimental results is shown.