Molecular Heat Engines: Quantum Coherence Effects

Feng Chen; Yi Gao; Michael Galperin

doi:10.3390/e19090472

Home/Archive/arXiv

arXiv · 1803.03312

Molecular Heat Engines: Quantum Coherence Effects

Feng Chen·Yi Gao·Michael Galperin

View original source ↗Read source document ↗Export metadata ↓

Abstract

Recent developments in nanoscale experimental techniques made it possible to utilize single molecule junctions as devices for electronics and energy transfer with quantum coherence playing an important role in their thermoelectric characteristics. Theoretical studies on the efficiency of nanoscale devices usually employ rate (Pauli) equations, which do not account for quantum coherence. Therefore, the question whether quantum coherence could improve the efficiency of a molecular device cannot be fully addressed within such considerations. Here, we employ a nonequilibrium Green function approach to study the effects of quantum coherence and dephasing on the thermoelectric performance of molecular heat engines. Within a generic bichromophoric donor-bridge-acceptor junction model, we show that quantum coherence may increase efficiency compared to quasi-classical (rate equation) predictions and that pure dephasing and dissipation destroy this effect.

Explore related subjects

cond-mat.mes-hall

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Feng Chen, Yi Gao, Michael Galperin. 2018-03-08. Molecular Heat Engines: Quantum Coherence Effects. https://doi.org/10.3390/e19090472

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Nanoscale Dipolar Fields in Artificial Spin Ice Probed by Scanning NV Magnetometry

We investigate dipolar coupling fields in two square-lattice artificial spin ice (ASI) systems with different lattice constants using scanning probe microscopy based on a single nitrogen-vacancy (NV) center in diamond. This technique offers unprecedented spatial resolution, operates under ambient condition, and provides quantitative stray field measurements, making it uniquely suited for studying nanoscale magnetic textures. Our approach combines fluorescence quenching imaging and continuous-wave optically detected magnetic resonance (cODMR). A comparison of the two ASI samples, which differ in their lattice constants of 1000 nm and 910 nm respectively, reveals differences in the appearance of ice-rule violations - deviations from the lowest energy configuration in ASI vertices. We attribute these variations to varying coupling strengths dictated by the lattice constant. From the cODMR data, we extract both axial and transverse components of the local magnetic field relative to the NV axis. Micromagnetic modeling of these measurements allows for an iterative determination of the external magnetic field orientation, the detection of subtle magnetization tilts induced by weak external fields (well below the nanomagnets' switching threshold), and an estimation of the effective saturation magnetization, thereby accounting for deviations in nanomagnet dimensions. These findings provide crucial insights into the tunable magnetic interactions in ASI, paving the way for the design of advanced magnonic and spintronic devices.

cond-mat.mes-hall↗

arXiv2026

Plasmon-driven electron-hole pair formation in a non-equilibrium Fermi liquid

Collective modes in Fermi liquids are usually regarded as dissipation channels that relax electronic excitations through Landau damping. Whether such modes can instead mediate the formation of correlated electronic states under non-equilibrium conditions remains an open question. Here, we show that under optical photo-doping, a bulk plasmon can drive correlated inter-band transfer within a transient electronic continuum. Using time- and angle-resolved photoemission spectroscopy (Tr-ARPES) on EuCd$_2$As$_2$ supported by electronic structure calculations, we observe that at high excitation density, plasmons transfer energy from a weakly dispersing bulk band into unoccupied surface states. This bulk-to-surface redistribution stabilizes a long-lived, energy-localized spectral feature consistent with a Mahan exciton. Our results reveal a non-equilibrium regime of Fermi-liquid physics in which collective modes do not merely dissipate energy, but also stabilize correlated bound states.

cond-mat.mes-hall↗

arXiv2026

Band offsets in InP/ZnSe nanocrystals evaluated using two-photon transitions analysis

We present a semi-analytical theoretical kp-study of the energy structure and optical transitions in spherical core-shell InP/ZnSe nanocrystals. We use the eight-band Kane model and the six-band Luttinger Hamiltonian in the spherical approximation to calculate the electron and hole energy spectra, respectively. The influence of the Coulomb interaction is considered perturbatively. The one- and two-photon absorption spectra are calculated as functions of the band offsets between the InP core and ZnSe shell. Exciton states responsible for the main features in the two-photon absorption spectra of InP/ZnSe nanocrystals are identified and the spectral dependence of the linear-circular dichroism signal is predicted. We show that in the presence of inhomogeneous broadening, the transition to the ground two-photon-active exciton state can be hidden behind intense transitions to higher-lying states. A comparison of the calculated one- and two-photon absorption spectra with the available experimental data shows that, depending on the lattice strain in the InP core, the range of possible valence band offsets is 0.85-1 eV. The determined range exceeds the natural valence band offset of 0.57 eV and indicates the presence of electric dipoles formed by the preferential Zn-P bonds at the InP/ZnSe heterointerface.

cond-mat.mes-hall↗