plasmaron
{{Short description|Quasiparticle}}
{{Use dmy dates|date=September 2023}}
In physics, the plasmaron was proposed by Lundqvist in 1967 as a quasiparticle arising in a system that has strong plasmon-electron interactions.Hedin, L., Lundqvist, B. & Lundqvist, S. New structure in the single-particle spectrum of an electron gas. Solid State Commun. 5, 237-239 (1967).{{cite journal|author1=Bengt Lundqvist |name-list-style=amp | title=Single-particle spectrum of the degenerate electron gas | journal=Physik der Kondensierten Materie| doi= 10.1007/BF02422717 |year=1967 | volume=6|issue=3 | pages=206–2017 |bibcode=1967PKM.....6..206L |s2cid=120588057 | url=https://link.springer.com/article/10.1007/BF02422717|url-access=subscription }} In the original work, the plasmaron was proposed to describe a secondary peak (or satellite) in the photoemission spectral function of the electron gas. More precisely it was defined as an additional zero of the quasi-particle equation . The same authors pointed out, in a subsequent work, that this extra solution might be an artifact of the used approximations:L. Hedin, B. I. Lundqvist, and S. Lundqvist, [https://doi.org/10.6028%2Fjres.074A.032 J Res Natl Bur Stand A Phys Chem. 74A, 417-431 (1970)]
{{blockquote|We want to stress again that the discussion we have given of the one-electron spectrum is based on the assumption that vertex corrections are small. As discussed in the next section recent work by Langreth [29] shows that vertex corrections in the core electron problem can have a quite large effect on the form of satellite structures, while their effect on the quasi particle properties seems to be small. Preliminary investigations by one of us (L.H.) show similar strong vertex effects on the conduction band satellite. The details of the plasmaron structure should thus not be taken very seriously.}} A more mathematical discussion is provided.{{cite journal | last1=Blomberg | first1=Clas | last2=Bergersen | first2=Birger | title=Spurious Structure from Approximations to the Dyson Equation | journal=Canadian Journal of Physics| volume=50 | issue=19 |year=1972| doi=10.1139/p72-303 | pages=2286–2293| bibcode=1972CaJPh..50.2286B }}{{cite journal | last1=Bergersen | first1=B. | last2=Kus | first2=F. W. | last3=Blomberg | first3=C. | title=Single Particle Green's Function in the Electron–Plasmon Approximation | journal=Canadian Journal of Physics| volume=51 | issue=1 |year=1973| doi=10.1139/p73-012 | pages=102–110| bibcode=1973CaJPh..51..102B }}
The plasmaron was also studied in more recent works in the literature.P. von Allmen [https://doi.org/10.1103/PhysRevB.46.13345 Phys. Rev. B 46, 13345 (1992)] It was shown, also with the support of the numerical simulations, that the plasmaron energy is an artifact of the approximation used to numerically compute the spectral function, e.g. solution of the dyson equation for the many body green function with a frequency dependent GW self-energy.F. Aryasetiawan, L. Hedin, and K. Karlsson, [https://doi.org/10.1103/PhysRevLett.77.2268 Phys. Rev. Lett. 77, 2268 (1996)] This approach give rise to a wrong plasmaron peak instead of the plasmon satellite which can be measured experimentally.
Despite this fact, experimental observation of a plasmaron was reported in 2010 for graphene.{{cite journal| author=Bostwick| last2=Speck| first2=F.| last3=Seyller| first3=T.| last4=Horn| first4=K.| last5=Polini| first5=M.| last6=Asgari| first6=R.| last7=MacDonald| first7=A. H.| last8=Rotenberg| first8=E. | title=Observation of Plasmarons in Quasi-Freestanding Doped Graphene | journal=Science | volume=328 | pages=999–1002 | doi=10.1126/science.1186489 | date=2010-05-21 | pmid=20489018|bibcode = 2010Sci...328..999B | issue=5981|display-authors=etal| hdl=11858/00-001M-0000-0011-2564-C| s2cid=206525211| url=http://edoc.mpg.de/534644| hdl-access=free}}
Also supported by earlier theoretical work.{{cite journal | last1=Polini | first1=Marco | last2=Asgari | first2=Reza | last3=Borghi | first3=Giovanni | last4=Barlas | first4=Yafis | last5=Pereg-Barnea | first5=T. | last6=MacDonald | first6=A. H. | title=Plasmons and the spectral function of graphene | journal=Physical Review B| volume=77 | issue=8 |year=2008| page=081411 | doi=10.1103/physrevb.77.081411| arxiv=0707.4230 | bibcode=2008PhRvB..77h1411P | s2cid=117935079 }} However subsequent works discussed that the theoretical interpretation of the experimental measure was not correct,{{cite journal | last1=Lischner | first1=Johannes | last2=Vigil-Fowler | first2=Derek | last3=Louie | first3=Steven G. | title=Physical Origin of Satellites in Photoemission of Doped Graphene: AnAb Initio
Observation of plasmaron peaks have also been reported in optical measurements of elemental bismuth{{cite journal|author1=Riccardo Tediosi |author2=N. P. Armitage |author3=E. Giannini |author4=D. van der Marel |name-list-style=amp | title=Charge Carrier Interaction with a Purely Electronic Collective Mode: Plasmarons and the Infrared Response of Elemental Bismuth | journal=Phys. Rev. Lett. | volume=27| issue=11| pages=711–714 | doi=10.1103/PhysRevLett.99.016406 |pmid=17678175 | date=1971-09-13 | bibcode=2007PhRvL..99a6406T|arxiv = cond-mat/0701447 |s2cid=18516062 |url=http://archive-ouverte.unige.ch/unige:24322 }} and in other optical measurements.{{cite journal | last1=Ban | first1=W J | last2=Wu | first2=D S | last3=Xu | first3=B | last4=Luo | first4=J L | last5=Xiao | first5=H | title=Revealing 'plasmaron' feature in DySb by optical spectroscopy study | journal=Journal of Physics: Condensed Matter| volume=31 | issue=40 |year=2019| doi=10.1088/1361-648x/ab2d1a | page=405701| pmid=31242466 | bibcode=2019JPCM...31N5701B | s2cid=195694609 | url=http://doc.rero.ch/record/327018/files/xu_rpf.pdf }}