اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSingle-molecule-mediated heat current between an electronic and a bosonic bath
191
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
In molecular devices electronic degrees of freedom are coupled to vibrational modes of the molecule, offering an opportunity to study fundamental aspects of this coupling between at the nanoscale. To this end we consider the nonequilibrium heat exchange between a conduction band and a bosonic bath mediated by a single molecule. For molecules large enough so that on-site interactions can be dropped we carry out an asymptotically exact calculation of the heat current, governed by the smallness of the electron-phonon coupling, and obtain the steady state heat current driven by a finite temperature drop. At low temperatures the heat current is found to have a power-law behavior with respect to the temperature difference with the power depending on the nature of the bosonic bath. At high temperatures, on the other hand, the current is linear in the temperature difference for all types of bosonic baths. The crossover between these behaviors is described. Some of the results are given a physical explanation by comparing to a perturbative Master equation calculation (whose limitation we examine).
قيم البحث
اقرأ أيضاً
A molecular wire containing an emitting molecular center is controllably suspended between the plasmonic electrodes of a cryogenic scanning tunneling microscope. Passing current through this circuit generates an ultra narrow-line emission at an energ
y of ? 1.5 eV which is assigned to the fluorescence of the molecular center. Control over the linewidth is obtained by progressively detaching the emitting unit from the surface. The recorded spectra also reveal several vibronic peaks of low intensities that can be viewed as a fingerprint of the emitter. Surface-plasmon localized at the tip-sample interface are shown to play a major role on both excitation and emission of the molecular excitons.
We present here a machine that is capable of extracting work from a single heat bath. Although no significant temperature gradient is involved in the operation of the machine, yet the Carnot efficiency as high as one is achievable. Working of the mac
hine is explained on the basis of a demon suggested by Maxwell. Utilizing the kinetic energy spectrum of the molecules in solution, the demon can send hotter molecules to a higher gravitational potential at the expense of their own energies. Difference in chemical potentials due to concentration gradients and use of semi-permeable membranes ensure the continuing cyclic process.
We introduce an algorithm for sampling many-body quantum states in Fock space. The algorithm efficiently samples states with probability approximately proportional to an arbitrary function of the second-quantized Hamiltonian matrix element connecting
the sampled state to the current state. We apply the new sampling algorithm to the recently-developed Semistochastic Full Configuration Interaction Quantum Monte Carlo method (S-FCIQMC), a semistochastic implementation of the power method for projecting out the ground state energy in a basis of Slater determinants. The heat-bath sampling requires modest additional computational time and memory compared to uniform sampling but results in newly-spawned weights that are approximately of the same magnitude, thereby greatly improving the efficiency of projection. A comparison in efficiency between uniform and approximate heat-bath sampling is performed on the all-electron nitrogen dimer at equilibrium in Dunnings cc-pVXZ basis sets with X in {D, T, Q, 5}, demonstrating a large gain in efficiency that increases with basis set size. In addition, a comparison in efficiency is performed on three all-electron first-row dimers, B_2, N_2, and F_2, in a cc-pVQZ basis, demonstrating that the gain in efficiency compared to uniform sampling also increases dramatically with the number of electrons.
The influence of multiple vibrational modes on current fluctuations in electron transport through single-molecule junctions is investigated. Our analysis is based on a generic model of a molecular junction, which comprises a single electronic state o
n the molecular bridge coupled to multiple vibrational modes and fermionic leads, and employs a master equation approach. The results reveal that in molecular junctions with multiple vibrational modes already weak to moderate electronic-vibrational coupling may result in high noise levels, especially at the onset of resonant transport, in accordance with experimental findings of Secker et al..[1] The underlying mechanisms are analyzed in some detail. [1] D. Secker et al., Phys. Rev. Lett. 106, 136807 (2011).
We extend our recently-developed heat-bath configuration interaction (HCI) algorithm, and our semistochastic algorithm for performing multireference perturbation theory, to the calculation of excited-state wavefunctions and energies. We employ time-r
eversal symmetry, which reduces the memory requirements by more than a factor of two. An extrapolation technique is introduced to reliably extrapolate HCI energies to the Full CI limit. The resulting algorithm is used to compute the twelve lowest-lying potential energy surfaces of the carbon dimer using the cc-pV5Z basis set, with an estimated error in energy of 30-50 {mu}Ha compared to Full CI. The excitation energies obtained using our algorithm have a mean absolute deviation of 0.02 eV compared to experimental values. We also calculate the complete active-space (CAS) energies of the S0, S1, and T0 states of tetracene, which are of relevance to singlet fission, by fully correlating active spaces as large as 18 electrons in 36 orbitals.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
