Abstract
We investigate the polaronic properties of a single impurity immersed in a weakly interacting bosonic environment confined within a one-dimensional double-well potential using an exact ...diagonalization approach. We find that an increase of the impurity–bath coupling results in a vanishing residue, signifying the occurrence of the polaron orthogonality catastrophe. Asymptotic configurations of the systems’ ground state wave function in the strongly interacting regime are obtained by means of a Schmidt decomposition, which in turn accounts for the observed orthogonality catastrophe of the polaron. We exemplify that depending on the repulsion of the Bose gas, three distinct residue behaviors appear with respect to the impurity–bath coupling. These residue regimes are characterized by two critical values of the bosonic repulsion and originate from the interplay between the intra- and the interband excitations of the impurity. Moreover, they can be clearly distinguished in the corresponding species reduced density matrices with the latter revealing a phase separation on either the one- or the two-body level. The impact of the interspecies mass-imbalance on the impurity’s excitation processes is appreciated yielding an interaction shift of the residue regions. Our results explicate the interplay of intra- and interband excitation processes for the polaron generation in multiwell traps and for designing specific polaron entangled states motivating their exposure in current experiments.
We theoretically investigate attractive and repulsive Fermi polarons in three dimensions at finite temperature and impurity concentration through the many-body T-matrix theory and high-temperature ...virial expansion. By using the analytically continued impurity Green’s function, we calculate the direct rf spectroscopy of attractive polarons in the unitary regime. Taking the peak value of the rf spectroscopy as the polaron energy and the full width half maximum as the polaron lifetime, we determine the temperature range of validity for the quasi-particle description of Fermi polarons in the unitary limit.
Organic thermoelectric (TE) materials are regarded as the next‐generation TE materials because of their merits including low cost, high mechanical flexibility, and low intrinsic thermal conductivity. ...However, their Seebeck coefficient is usually quite low. Herein, a new strategy is demonstrated to greatly enhance the Seebeck coefficient of poly(3,4‐ethylenedioxy‐thiophene):poly(styrenesulfonate) (PEDOT:PSS), which is the most popular TE polymer, through polaron level splitting via π–π overlapping with nonpolar small aromatic molecules including anthracene, naphthalene, and pyrene. Although these aromatic molecules are neither oxidizing nor reducing agent, they can greatly enhance the Seebeck coefficient of PEDOT:PSS films pre‐treated with dimethyl sulfoxide, acid, or acid then base, while they do not lower the electrical conductivity too much. Through such a treatment with anthracene, the Seebeck coefficient can be up to 45.5 µV K−1, and the ZT value can be up to 0.27. The enhancement is ascribed to the splitting of the lower polaron energy level of PEDOT, which is induced by the π–π overlapping between the aromatic compounds and conjugated PEDOT. This can shift up the Fermi level, thereby enhancing the Seebeck coefficient.
Treating poly(3,4‐ethylenedioxy‐thiophene) (PEDOT):poly(styrenesulfonate) with a nonpolar conjugated molecule like anthracene can greatly enhance the Seebeck coefficient. Because these molecules have neither reducing nor oxidizing capability, the Seebeck coefficient enhancement is attributed to the π–π overlapping between aromatic molecule and conjugated PEDOT, which can induce the splitting of the lower polaron level and lift the Fermi level of PEDOT.
In this study, the role of Pb substitution on the microstructural and magneto-transport properties of the double layered manganites LaSm0.4Ca1.6-xPbxMn2O7 (x = 0, 0.1 and 0.2), prepared by the ...solid-state reaction method, was investigated. On the samples, X-Ray Diffraction, Scanning Electron Microscopy and resistivity as a function of temperature measurements were performed. XRD measurements revealed that the samples crystallized in a tetragonal phase with an I4/mmm space group and that the lattice parameters increased with increasing Pb content. SEM measurements indicated the granular character and the average grain sizes ranged between 0.5 and 4 μm for all the samples. The temperature dependence of resistivity of all the samples shows insulating-like behavior for the studied range of temperature (T > 100 K). The maximum magnetoresistance (MR%) value was found to be 31.95% at 100 K for the sample with x = 0, while it was 11% and 8% for the samples with x = 0.1 and 0.2, respectively. The resistivity curves are found to be well described by the Adiabatic Small Polaron Model in the range and Mott's 3D Variable Range Hopping model in the range. The density of states near the Fermi level (DOS), mean hopping distance, and mean hopping energy values were computed in the range, and the role of Pb substitution on these parameters was discussed as well.
•Detailed analysis of magnetotransport properties of double layered manganite LaSm0.4Ca1.6-xPbxMn2O7 (x = 0, 0.1 and 0.2).•XRD profiles revealed the Ruddlesden-popper phase in LaSm0.4Ca1.6-xPbxMn2O7 (x = 0, 0.1 and 0.2) compounds.•Adiabatic Small Polaron hopping and Mott's 3D Variable Range Hopping describe well the high temperature range resistivity.•The density of state near Fermi level N(EF), hopping distance Rh and the hopping energy Eh were estimated and discussed.
Abstract
We investigate the formation of magnetic Bose polaron, an impurity atom dressed by spin-wave excitations, in a one-dimensional spinor Bose gas. Within an effective potential model, the ...impurity is strongly confined by the host excitations which can even overcome the impurity-medium repulsion leading to a self-localized quasi-particle state. The phase diagram of the attractive and self-bound repulsive magnetic polaron, repulsive non-magnetic (Fröhlich-type) polaron and impurity-medium phase-separation regimes is explored with respect to the Rabi-coupling between the spin components, spin–spin interactions and impurity-medium coupling. The residue of such magnetic polarons decreases substantially in both strong attractive and repulsive branches with strong impurity-spin interactions, illustrating significant dressing of the impurity. The impurity can be used to probe and maneuver the spin polarization of the magnetic medium while suppressing ferromagnetic spin–spin correlations. It is shown that mean-field theory fails as the spinor gas approaches immiscibility since the generated spin-wave excitations are prominent. Our findings illustrate that impurities can be utilized to generate controllable spin–spin correlations and magnetic polaron states which can be realized with current cold atom setups.
We report the synthesis, transport measurements, and electronic structure of conjugation-broken oligophenyleneimine (CB-OPI 6) molecular wires with lengths of ∼4 nm. The wires were grown from Au ...surfaces using stepwise aryl imine condensation reactions between 1,4-diaminobenzene and terephthalaldehyde (1,4-benzenedicarbaldehyde). Saturated spacers (conjugation breakers) were introduced into the molecular backbone by replacing the aromatic diamine with trans-1,4-diaminocyclohexane at specific steps during the growth processes. FT-IR and ellipsometry were used to follow the imination reactions on Au surfaces. Surface coverages (∼4 molecules/nm2) and electronic structures of the wires were determined by cyclic voltammetry and UV–vis spectroscopy, respectively. The current–voltage (I–V) characteristics of the wires were acquired using conducting probe atomic force microscopy (CP-AFM) in which an Au-coated AFM probe was brought into contact with the wires to form metal-molecule-metal junctions with contact areas of ∼50 nm2. The low bias resistance increased with the number of saturated spacers, but was not sensitive to the position of the spacer within the wire. Temperature dependent measurements of resistance were consistent with a localized charge (polaron) hopping mechanism in all of the wires. Activation energies were in the range of 0.18–0.26 eV (4.2–6.0 kcal/mol) with the highest belonging to the fully conjugated OPI 6 wire and the lowest to the CB3,5-OPI 6 wire (the wire with two saturated spacers). For the two other wires with a single conjugation breaker, CB3-OPI 6 and CB5-OPI 6, activation energies of 0.20 eV (4.6 kcal/mol) and 0.21 eV (4.8 kcal/mol) were found, respectively. Computational studies using density functional theory confirmed the polaronic nature of charge carriers but predicted that the semiclassical activation energy of hopping should be higher for CB-OPI molecular wires than for the OPI 6 wire. To reconcile the experimental and computational results, we propose that the transport mechanism is thermally assisted polaron tunneling in the case of CB-OPI wires, which is consistent with their increased resistance.
On polaron stability in Ag-doped ZnO films Sarkisian, A. R.; Aghamalyan, N. R.; Nersisyan, M. N. ...
Applied physics. A, Materials science & processing,
03/2024, Volume:
130, Issue:
3
Journal Article
Peer reviewed
The MIR reflectivity spectra ranging from 4000 to 900 cm
−1
of the polarons in zinc oxide films doped with 0.24 at.% silver (AgZnO) as a function of temperature (190–360 K) in weakly concentrated ...gaseous methane environment were obtained. The decay rate, energy and intensity of polaron states at 1248 and 1484 cm
–1
are analyzed using the Lorentzian line-shape function. The lines show the redshift (~ 3%) with an increase in temperature. The width and intensity of the line at 1248 cm
–1
decrease by 23% and 38%, respectively, with an increase in temperature to 360 K. The one-phonon line at 1484 cm
–1
broadens by ~ 50%, and the intensity decreases by 54% upon reaching a temperature of 330 K, and at T ≥ 350 K, the line 1484 cm
–1
decays into many ultrafine weakly localized states due to the formation of a hydrocarbon adsorbate, which acts as a charge trapping center on the AgZnO surface. The calculated polaron scattering time
τ
= 2.2 fs decreases to 1.8 fs as the temperature rises from 250 to 360 K. The frequency dependences of the optical conductivity determined by Kramers–Kronig relations show a localization-delocalization crossover near 1900 cm
–1
. At frequencies below 1900 cm
–1
, the carriers are localized, and dc-conductivity satisfies the criterion of the Mott-VRH model with the hopping energy of 0.43 T
3/4
meV.
A novel approach for developing shortwave IR (SWIR) organic photodiodes (OPDs) using doped polymers is presented. SWIR OPDs are challenging to produce because of the limitations in extending the ...absorption of conjugated molecules and the high dark currents of SWIR‐absorbing materials. Herein, it is shown that the conversion of bound polarons to free polarons by light energy can be utilized as an SWIR photodetection mechanism. To maximize the bound‐polaron density and bound‐to‐free polaron ratio of the doped polymer film, the doping process is engineered and dopant molecules are diffused into the crystalline domain of the polymer matrix and a direct correlation between the bound‐to‐free polaron ratio and device performance is confirmed. The optimized double‐doped SWIR OPD exhibits a high external quantum efficiency of 77 100% and specific detectivity of 1.11 × 1011 Jones against SWIR. These findings demonstrate the application potential of polarons as alternatives for Frenkel excitons in SWIR OPDs.
A novel approach for the development of shortwave IR (SWIR) organic photodiodes by employing chemical doping of organic semiconductors is presented. Once the bound‐to‐polaron ratios of doped polymer semiconductors are optimized, SWIR absorption has the capability to alter these ratios, thereby enabling the measurement of photocurrent generated by SWIR illumination, up to 1800 nm.
Abstract
In this work, we consider the motion of a polaron in a polynucleotide Holstein molecular chain in a constant electric field. It is shown that the character of the polaron motion in the chain ...depends not only on the chosen parameters of the chain, but also on the initial distribution of the charge along the chain. It is shown that for a small set value of the electric field intensity and for fixed values of the chain parameters, changing only the initial distribution of the charge in the chain, it is possible to observe either a uniform movement of the charge along the chain, or an oscillatory mode of charge movement.
In this work, the Pb(Zr0.2Ti0.8)O3/(La0.67Ca0.33)MnO3 heterostructure film is deposited on the Pt/Ti/SiO2/Si wafer. The dominant transport is the inelastic hopping conduction. Due to the interaction ...between ferroelectric domain and magnetic polaron, film still exhibits weak ferromagnetism above the Curie temperature. Under lower bias voltage, the non-zero sequential magnetoresistance occurs on the magnetic granular junction. As soon as bias voltage exceeds the coercive voltage, the ferroelectric domain is aligned, consequently the magnetoresistance tends to vanish. Such electric switch of magnetoresistance is potential for the electric-write magnetic-read storage device.
•The ferroelectric domain interacts with magnetic polaron on PZT/LCMO interface.•The above-TC ferromagnetism exists in PZT/LCMO heterostructure.•The magnetoresistance is switched by voltage in PZT/LCMO heterostructure.
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