arXiv subjects

Pawel Wojcik

Publications and source records attributed to Pawel Wojcik.

7 recordsLinked to original sources

arXiv2025

Unraveling vibronic interactions in molecules functionalized with optical cycling centers

We report detailed characterization of the vibronic interactions between the first two electronically excited states, A and B, in SrOPh (Ph = phenyl, -C6H5) and its deuterated counterpart, SrOPh-d5 (-C6D5). The vibronic interactions, which arise due to non-adiabatic coupling between the two electronic states, mix the B,v0 state with the energetically close vibronic level A,v21v33, resulting in extra transition probability into the latter state. This state mixing is more prominent in the deuterated molecule because of the smaller energy gap between the interacting states. We model the mixing of the A and B states using the Koppel-Domcke-Cederbaum (KDC) Hamiltonian parametrized in the diabatic framework of Ichino, Gauss, and Stanton on the basis of equation-of-motion coupled-cluster calculations. The simulation attributes the observed mixing to a second-order effect mediated by linear quasi-diabatic couplings between the A-C and B-C states. Based on the measured spectra, we deduce an effective coupling strength of 0.5 cm-1. Non-adiabatic couplings between different electronic states is an important factor that should be considered in the design of laser-cooling protocols for complex molecules.

physics.chem-ph↗

arXiv2025

Vibronic coupling limits the use of high-lying electronic states in complex molecules for laser cooling

Laser cooling of large, complex molecules is a long-standing goal, instrumental for enabling new quantum technology and precision measurements. A primary consideration for the feasibility of laser cooling, which determines the efficiency and technical requirements of the process, is the number of excited-state decay pathways leading to vibrational excitations. Therefore, the assessment of the laser-cooling potential of a molecule begins with estimate of the vibrational branching ratios of the first few electronic excited states theoretically to find the optimum cooling scheme. Such calculations, typically done within the BO and harmonic approximations, have suggested that one leading candidate for large, polyatomic molecule laser cooling, alkaline earth phenoxides, can most efficiently be laser-cooled via the third electronically excited C state. Here, we report the first detailed spectroscopic characterization of the C state in CaOPh and SrOPh. We find that nonadiabatic couplings between the A, B, and C states lead to substantial mixing, giving rise to vibronic states that enable additional decay pathways. Based on the intensity ratio of these extra decay channels, we estimate a non-adiabatic coupling strength of 0.1 cm-1. While this coupling strength is small, the large density of vibrational states available at photonic energy scales in a polyatomic molecule leads to significant mixing. Thus, this result is expected to be general for large molecules and implies that only the lowest electronic excited state should be considered when judging the suitability of a molecule for laser cooling.

physics.atom-ph↗

arXiv2021

From norm derivatives to orthogonalities in Hilbert $C^*$-modules

Let $\big(\mathscr{X}, \langle\cdot, \cdot\rangle\big)$ be a Hilbert $C^*$-module over a $C^*$-algebra $\mathscr{A}$ and let $\mathcal{S}(\mathscr{A})$ be the set of states on $\mathscr{A}$. In this paper, we first compute the norm derivative for elements $x$ and $y$ of $\mathscr{X}$ as follows \begin{align*} ρ_{_{+}}(x, y) = \max\Big\{\mbox{Re}\,φ(\langle x, y\rangle): \, φ\in \mathcal{S}(\mathscr{A}), φ(\langle x, x\rangle) = \|x\|^2\Big\}. \end{align*} We then apply it to characterize different concepts of orthogonality in $\mathscr{X}$. In particular, we present a simpler proof of the classical characterization of Birkhoff--James orthogonality in Hilbert $C^*$-modules. Moreover, some generalized Daugavet equation in the $C^*$-algebra $\mathbb{B}(\mathcal{H})$ of all bounded linear operators acting on a Hilbert space $\mathcal{H}$ is solved.

math.OA↗

arXiv2021

Orthogonality Hilbert A-modules and operators preserving multi-A-linearity

In this paper we present results concerning orthogonality in Hilbert $C^*$-modules. Moreover, for a $C^*$-algebra $\mathscr{A}$, we prove theorems concerning the multi-$\mathscr{A}$-linearity and its preservation by $\mathscr{A}$-linear operators. New version of solution of the orthogonality equation on Hilbert $C^*$-modules and mappings preserving orthogonality are also investigated.

math.OA↗

arXiv2020

Numerical radius orthogonality in $C^*$-algebras

In this paper we characterize the Birkhoff--James orthogonality with respect to the numerical radius norm $v(\cdot)$ in $C^*$-algebras. More precisely, for two elements $a, b$ in a $C^*$-algebra $\mathfrak{A}$, we show that $a\perp_{B}^{v} b$ if and only if for each $θ\in [0, 2π)$, there exists a state $φ_{_θ}$ on $\mathfrak{A}$ such that $|φ_{_θ}(a)| = v(a)$ and $\mbox{Re}\big(e^{iθ}\overline{φ_{_θ}(a)}φ_{_θ}(b)\big)\geq 0$. Moreover, we compute the numerical radius derivatives in $\mathfrak{A}$. In addition, we characterize when the numerical radius norm of the sum of two (or three) elements in $\mathfrak{A}$ equals the sum of their numerical radius norms.

math.FA↗

arXiv2013

Periodicity of resonant tunneling current induced by the Stark resonances in semiconductor nanowire

The modification of the electronic current resulting from Stark resonances has been studied for the semiconductor nanowire with the double-barrier structure. Based on the calculated current-voltage characteristics we have shown that the resonant tunneling current is a periodic function of the width of the spacer layer. We have also demonstrated that the simultaneous change of the source-drain voltage and the voltage applied to the gate located near the nanowire leads to almost periodic changes of the resonant tunneling current as a function of the source-drain and gate voltages. The periodic properties of the resonant tunneling current result from the formation of the Stark resonance states. If we change the electric field acting in the nanowire, the Stark states periodically acquire the energies from the transport window and enhance the tunneling current in a periodic manner. We have found that the separations between the resonant current peaks on the source-drain voltage scale can be described by a slowly increasing linear function of the Stark state quantum number. This allows us to identify the quantum states that are responsible for the enhancement of the resonant tunneling. We have proposed a method of the experimental observation of the Stark resonances in semiconductor double-barrier heterostructures.

cond-mat.mes-hall↗

arXiv2012

Intrinsic oscillations of spin current polarization in a paramagnetic resonant tunneling diode

A spin- and time-dependent electron transport has been studied in a paramagnetic resonant tunneling diode using the self-consistent Wigner-Poisson method. Based on the calculated current-voltage characteristics in an external magnetic field we have demonstrated that under a constant bias both the spin-up and spin-down current components exhibit the THz oscillations in two different bias voltage regimes. We have shown that the oscillations of the spin-up (down) polarized current result from the coupling between the two resonance states: one localized in the triangular quantum well created in the emitter region and the second localized in the main quantum well. We have also elaborated the one-electron model of the current oscillations, which confirms the results obtained with the Wigner-Poisson method. The spin current oscillations can lower the effectiveness of spin filters based on the paramagnetic resonant tunneling structures and can be used to design the generators of the spin polarized current THz oscillations that can operate under the steady bias and constant magnetic field.

cond-mat.mes-hall↗