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Verma P, Budkina DS, Vauthey E. Photoinduced Electron Transfer between Dipolar Reactants: Solvent and Excitation Wavelength Effects. J Phys Chem B 2024; 128:1231-1240. [PMID: 38265415 DOI: 10.1021/acs.jpcb.3c07922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
Electron transfer (ET) quenching in nonpolar media is not as well understood as in polar environments. Here, we investigate the effect of dipole-dipole interactions between the reactants using ultrafast broadband electronic spectroscopy combined with molecular dynamics simulations. We find that the quenching of the S1 state of two polar dyes, coumarin 152a and Nile red, by the polar N,N-dimethylaniline (DMA) in cyclohexane is faster by a factor up to 3 when exciting on the red edge rather than at the maximum of their S1 ← S0 absorption band. This originates from the inhomogeneous broadening of the band due to a distribution of the number of quencher molecules around the dyes. As a consequence, red-edge excitation photoselects dyes in a DMA-rich environment. Such broadening is not present in acetonitrile, and no excitation wavelength dependence of the ET dynamics is observed. The quenching of both dyes is markedly faster in nonpolar than polar solvents, independently of the excitation wavelength. According to molecular dynamics simulations, this is due to the preferential solvation of the dyes by DMA in cyclohexane. The opposite preferential solvation is predicted in acetonitrile. Consequently, close contact between the reactants in acetonitrile requires partial desolvation. By contrast, the recombination of the quenching product is slower in nonpolar than in polar solvents and exhibits much smaller dependence, if any, on the excitation wavelength.
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Affiliation(s)
- Pragya Verma
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland
| | - Darya S Budkina
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland
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Bhattacharya A, Bhardwaj V, Mani BK, Dutt JK, Chatterjee R. Strain-tunable triple point Fermions in diamagnetic rare-earth half-Heusler alloys. Sci Rep 2021; 11:12029. [PMID: 34103556 PMCID: PMC8187712 DOI: 10.1038/s41598-021-90850-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 05/10/2021] [Indexed: 11/09/2022] Open
Abstract
Topologically non-trivial electronic structure is a feature of many rare-earth half-Heusler alloys, which host atoms with high spin-orbit coupling bringing in the non-triviality. In this article, using the first-principles simulations, rare-earth half-Heusler YPdBi, ScPdBi, LaPdBi, LuPdBi, YPtBi and LuPtBi alloys are studied under strain to reveal multiple band inversions associated with topological phase transitions. From our simulations we find that, as a result of first band-inversion, the Brillouin zone of the diamagnetic half-Heusler alloys hosts eight triple points whereas, the second band inversion causes the emergence of sixteen more triple points. These band-inversions are observed to be independent of the spin-orbit coupling and are the reason behind increasing occupation of bismuth 7s orbitals as volume of the unit cell increases. The surface electronic transport in different triple point semi-metallic phases is found to evolve under strain, as the number of Fermi arcs change due to multiple band inversions. Once the second band inversion occurs, further application of tensile strain does not increase the number of triple points and Fermi arcs. However, increasing tensile strain (or decreasing compressive strain) pushes the triple point crossing to higher momenta, making them more effective as source of highly mobile electrons. These observations make a pathway to tune the bulk as well as surface transport through these semi-metals by application of tensile or compressive strain depending on the unstrained relative band-inversion strength of the material.
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Affiliation(s)
- Anupam Bhattacharya
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, India
| | - Vishal Bhardwaj
- Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
| | - Brajesh K Mani
- Department of Physics, Indian Institute of Technology Delhi, New Delhi, India.
| | - Jayanta K Dutt
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, India
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Bhardwaj V, Bhattacharya A, Srivastava S, Khovaylo VV, Sannigrahi J, Banerjee N, Mani BK, Chatterjee R. Strain driven emergence of topological non-triviality in YPdBi thin films. Sci Rep 2021; 11:7535. [PMID: 33824352 PMCID: PMC8024271 DOI: 10.1038/s41598-021-86936-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 03/22/2021] [Indexed: 02/01/2023] Open
Abstract
Half-Heusler compounds exhibit a remarkable variety of emergent properties such as heavy-fermion behaviour, unconventional superconductivity and magnetism. Several of these compounds have been predicted to host topologically non-trivial electronic structures. Remarkably, recent theoretical studies have indicated the possibility to induce non-trivial topological surface states in an otherwise trivial half-Heusler system by strain engineering. Here, using magneto-transport measurements and first principles DFT-based simulations, we demonstrate topological surface states on strained [110] oriented thin films of YPdBi grown on (100) MgO. These topological surface states arise in an otherwise trivial semi-metal purely driven by strain. Furthermore, we observe the onset of superconductivity in these strained films highlighting the possibility of engineering a topological superconducting state. Our results demonstrate the critical role played by strain in engineering novel topological states in thin film systems for developing next-generation spintronic devices.
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Affiliation(s)
- Vishal Bhardwaj
- Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
| | - Anupam Bhattacharya
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, India
| | - Shivangi Srivastava
- Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
| | - Vladimir V Khovaylo
- National University of Science and Technology "MISiS", Moscow, Russia, 119049
| | - Jhuma Sannigrahi
- Department of Physics, Loughborough University, Loughborough, LE11 3TU, UK
| | - Niladri Banerjee
- Department of Physics, Loughborough University, Loughborough, LE11 3TU, UK.
| | - Brajesh K Mani
- Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
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Nançoz C, Rumble C, Rosspeintner A, Vauthey E. Bimolecular photoinduced electron transfer in non-polar solvents beyond the diffusion limit. J Chem Phys 2020; 152:244501. [PMID: 32610996 DOI: 10.1063/5.0012363] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Electron transfer (ET) quenching dynamics in non-polar solvents are investigated using ultrafast spectroscopy with a series of six fluorophore/quencher pairs, covering a driving force range of more than 1.3 eV. The intrinsic ET rate constants, k0, deduced from the quenching dynamics in the static regime, are of the order of 1012-1013 M-1 s-1, i.e., at least as large as in acetonitrile, and do not exhibit any marked dependence on the driving force. A combination of transient electronic and vibrational absorption spectroscopy measurements reveals that the primary product of static quenching is a strongly coupled exciplex that decays within a few picoseconds. More weakly coupled exciplexes with a longer lifetime are generated subsequently, during the dynamic, diffusion-controlled, stage of the quenching. The results suggest that static ET quenching in non-polar solvents should be viewed as an internal conversion from a locally excited state to a charge-transfer state of a supermolecule rather than as a non-adiabatic ET process.
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Affiliation(s)
- Christoph Nançoz
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Christopher Rumble
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
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Mukherjee P, Sen P. Decoupling diffusion from the bimolecular photoinduced electron transfer reaction: a combined ultrafast spectroscopic and kinetic analysis. Phys Chem Chem Phys 2017; 19:11220-11229. [DOI: 10.1039/c7cp01387f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We have studied the bimolecular photoinduced electron transfer (PET) reaction between benzophenone (Bp) and DABCO using femtosecond broadband transient absorption spectroscopy in different compositions of acetonitrile/1-butanol binary solvent mixtures.
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Affiliation(s)
- Puspal Mukherjee
- Department of Chemistry
- Indian Institute of Technology Kanpur
- Kanpur
- India
| | - Pratik Sen
- Department of Chemistry
- Indian Institute of Technology Kanpur
- Kanpur
- India
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Kumpulainen T, Lang B, Rosspeintner A, Vauthey E. Ultrafast Elementary Photochemical Processes of Organic Molecules in Liquid Solution. Chem Rev 2016; 117:10826-10939. [DOI: 10.1021/acs.chemrev.6b00491] [Citation(s) in RCA: 249] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Tatu Kumpulainen
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Bernhard Lang
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
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Angulo G, Rosspeintner A, Koch M, Vauthey E. Comment on "Observation of the Marcus Inverted Region for Bimolecular Photoinduced Electron-Transfer Reactions in Viscous Media". J Phys Chem B 2016; 120:9800-3. [PMID: 27536949 DOI: 10.1021/acs.jpcb.6b06610] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gonzalo Angulo
- Institute of Physical Chemistry, Polish Academy of Sciences , 44/52 Kasprzaka, 01-224 Warsaw, Poland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Marius Koch
- Department of Chemistry, Princeton University , 08540 Princeton, New Jersey, United States
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
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Meinert M. Unconventional Superconductivity in YPtBi and Related Topological Semimetals. PHYSICAL REVIEW LETTERS 2016; 116:137001. [PMID: 27081999 DOI: 10.1103/physrevlett.116.137001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Indexed: 06/05/2023]
Abstract
YPtBi, a topological semimetal with a very low carrier density, was recently found to be superconducting below T_{c}=0.77 K. In conventional theory, the nearly vanishing density of states around the Fermi level would imply a vanishing electron-phonon coupling and would, therefore, not allow for superconductivity. Based on relativistic density-functional theory calculations of the electron-phonon coupling in YPtBi, it is found that carrier concentrations of more than 10^{21} cm^{-3} are required to explain the observed critical temperature with the conventional pairing mechanism, which is several orders of magnitude larger than experimentally observed. It is very likely that an unconventional pairing mechanism is responsible for the superconductivity in YPtBi and related topological semimetals with half-Heusler structure.
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Affiliation(s)
- Markus Meinert
- Center for Spinelectronic Materials and Devices, Bielefeld University, D-33501 Bielefeld, Germany
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NMR Evidence for the Topologically Nontrivial Nature in a Family of Half-Heusler Compounds. Sci Rep 2016; 6:23172. [PMID: 26980406 PMCID: PMC4793261 DOI: 10.1038/srep23172] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 02/25/2016] [Indexed: 11/09/2022] Open
Abstract
Spin-orbit coupling (SOC) is expected to partly determine the topologically nontrivial electronic structure of heavy half-Heusler ternary compounds. However, to date, attempts to experimentally observe either the strength of SOC or how it modifies the bulk band structure have been unsuccessful. By using bulk-sensitive nuclear magnetic resonance (NMR) spectroscopy combined with first-principles calculations, we reveal that 209Bi NMR isotropic shifts scale with relativity in terms of the strength of SOC and average atomic numbers, indicating strong relativistic effects on NMR parameters. According to first-principles calculations, we further claim that nuclear magnetic shieldings from relativistic p1/2 states and paramagnetic contributions from low-lying unoccupied p3/2 states are both sensitive to the details of band structures tuned by relativity, which explains why the hidden relativistic effects on band structure can be revealed by 209Bi NMR isotropic shifts in topologically nontrivial half-Heusler compounds. Used in complement to surface-sensitive methods, such as angle resolved photon electron spectroscopy and scanning tunneling spectroscopy, NMR can provide valuable information on bulk electronic states.
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