Elastic response of [111]-tunnelling impurities

Nalbach, P.; Terzidis, O.; Topp, K. A.; Würger, Aloïs

doi:10.1088/0953-8984/13/7/310

Cited by 9 publications

(26 citation statements)

References 25 publications

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“…For weak defect-phonon coupling  W 1, where edge tunneling dominates, an energy spectrum as depicted in figure 1(a) results. The dynamic dielectric and acoustic response for this case have been discussed previously [23].…”

Section: Polaron Transformationmentioning

confidence: 94%

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Symmetry reduction for tunneling defects due to strong couplings to phonons

Nalbach

Schechter

2017

New J. Phys.

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Tunneling two-level systems (TLSs) are ubiquitous in amorphous solids, and form a major source of noise in systems such as nano-mechanical oscillators, single electron transistors, and superconducting qubits. Occurance of defect tunneling despite their coupling to phonons is viewed as a hallmark of weak defect-phonon coupling. This is since strong coupling to phonons results in significant phonon dressing and suppresses tunneling in two-level tunneling defects effectively. Here we determine the dynamics of a tunneling defect in a crystal strongly coupled to phonons incorporating the full 3D geometry in our description. We find that inversion symmetric tunneling is not dressed by phonons whereas other tunneling pathways are dressed by phonons and, thus, are suppressed by strong defectphonon coupling. We provide the linear acoustic and dielectric response functions for a tunneling defect in a crystal for strong defect-phonon coupling. This allows direct experimental determination of the defect-phonon coupling. The singling out of inversion-symmetric tunneling states in single tunneling defects is complementary to their dominance of the low energy excitations in strongly disordered solids as a result of inter-defect interactions for large defect concentrations. This suggests that inversion symmetric TLSs play a unique role in the low energy properties of disordered solids.

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Section: Polaron Transformationmentioning

confidence: 94%

“…The elastic strain at the defect position r due to phonons [17,23] is determined as spatial derivative…”

Section: Defect-phonon Couplingmentioning

confidence: 99%

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Symmetry reduction for tunneling defects due to strong couplings to phonons

Nalbach

Schechter

2017

New J. Phys.

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“…The dynamic response of an isolated ͓111͔ quantum impurity has recently been studied by Nalbach et al, 33 and has been applied to these data. They were able to explain the sound velocity for the smallest CN Ϫ doping in KCl, 45 ppm, shown here in Fig.…”

Section: A Unstrained Hostsmentioning

confidence: 99%

“…Also shown is the coupling energy ␥ t of CN in KCl in the dilute limit from Ref. 33. Values for (KBr) 1Ϫx (KCN) x and a-SiO 2 are included for comparison.…”

Section: B Strained Hostsmentioning

confidence: 99%

Tunneling states in strained alkali-halide crystals containingCN−ions

Topp

Pohl

2002

Phys. Rev. B

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Torsional oscillators (ϳ90 kHz) have been used between 0.06 and 100 K to study low-energy excitations in strained alkali-halide hosts doped with KCN in the concentration range from 0.2 to 5 mol %. The tunneling model, originally developed to describe the low-temperature thermal and elastic anomalies in amorphous solids, has been found to describe our data very well. From the observation that the tunneling strength varies linearly with the KCN concentration, we conclude that random internal stresses in the hosts, rather than interactions between the dopant ions, lead to the tunneling states. Implications for the origin of the tunneling states in amorphous solids and in highly disordered crystals, and also for their universality are considered.

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Role of Spatially Correlated Fluctuations in Photosynthetic Excitation Energy Transfer with an Equilibrium and a Nonequilibrium Initial Bath

Qin

Cui

et al. 2021

J. Phys. Chem. B

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The transfer of excitation energy in photosynthetic light-harvesting complexes has inspired growing interest for its scientific and engineering significance. Recent experimental findings have suggested that spatially correlated environmental fluctuations may account for the existence of long-lived quantum coherent energy transfer observed even at physiological temperature. In this paper, we investigate the effects of spatial correlations on the excitation energy transfer dynamics by including a nonequilibrium initial bath in a simulated donor–acceptor model. The initial bath state, which is assumed to be either equilibrium or nonequilibrium, is expanded in powers of coupling strength within the polaron formalism of a quantum master equation. The spatial correlations of bath fluctuations strongly influence the decay of coherence in the dynamics. The role of a nonequilibrium initial bath is also influenced by spatial correlations and becomes the most conspicuous for certain degrees of spatial correlations from which we propose a picture that the spatial correlations of bath fluctuations open up new energy transfer pathways, playing a role of protecting coherence. Besides, we apply the polaron master equation approach to study the dynamics in a two-site subsystem of the FMO complex and provide a practical example that shows the versatility of this approach.

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Elastic response of [111]-tunnelling impurities

Cited by 9 publications

References 25 publications

Symmetry reduction for tunneling defects due to strong couplings to phonons

Symmetry reduction for tunneling defects due to strong couplings to phonons

Tunneling states in strained alkali-halide crystals containingCN−ions

Role of Spatially Correlated Fluctuations in Photosynthetic Excitation Energy Transfer with an Equilibrium and a Nonequilibrium Initial Bath

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