Editing Photoelectric effect (section)

===21st century===
Research in recent years on the photoelectric effect has been focused on measurements on emission time of photoelectrons. For long, it was believed that photoemission is an instantaneous process. However, a seminal role in this field was played by experimental techniques on attosecond generation of pulses of light for studies on electron dynamics, which was recognised through the 2023 Nobel Prize in physics to Pierre Agostini, Ferenc Krausz and Anne L’Huillier.<ref name="NP">{{cite journal |title=Light as fast as electrons |journal=[[Nat. Phys.]] |volume=19 |year=2023 |issue=11 |pages=1520 |doi=10.1038/s41567-023-02305-y |bibcode=2023NatPh..19.1520. }}</ref> For example, in 2010, it was discovered that electron emission takes 20 attoseconds and that photoemission is associated with complex multielectron correlations and is not a single-electron process.<ref name="Schultze">{{cite journal |title=Delay in Photoemission , 1889-1911 |last1=Schultze |first1=M. |journal=[[Science (journal)|Science]] |volume=328 |year=2010 |issue=5986 |pages=1658–1662 |doi=10.1126/science.1189401|pmid=20576884 |url=https://mediatum.ub.tum.de/1579410 }}</ref> In a more recent work in the context of [[tungsten]], measurements on photoelectron emission indicated that around 100 [[attosecond]]s are required to liberate an electron.<ref name="Cavalieri">{{cite journal |title=Attosecond spectroscopy in condensed matter |last1=Cavalieri |first1=A. L. |last2=Müller |first2=N. |last3=Uphues |first3=Th. |last4=Yakovlev |first4=V. S. |last5=Baltuška |first5=A. |last6=Horvath |first6=B. |last7=Schmidt |first7=B. |last8=Blümel |first8=L. |last9=Holzwarth |first9=R. |last10=Hendel |first10=S. |last11=Drescher |first11=M. |last12=Kleineberg |first12=U. |last13=Echenique |first13=P. M. |last14=Kienberger |first14=R. |last15=Krausz |first15=F. |last16=Heinzmann |first16=U. |display-authors=5 |journal=[[Nature (journal)|Nature]] |volume=449 |year=2007 |issue=7165 |pages=1029–1032|doi=10.1038/nature06229|pmid=17960239 |bibcode=2007Natur.449.1029C }}</ref> In another research, the value was found to be 45 attoseconds.<ref name="Ossiander">{{cite journal |title=Absolute timing of the photoelectric effect, 1889-1911 |last1=Ossiander |first1=M. |last2=Riemensberger |first2=J. |last3=Neppl |first3=S. |last4=Mittermair |first4=M. |last5=Schäffer |first5=M. |last6=Duensing |first6=A. |last7=Wagner |first7=M. S. |last8=Heider |first8=R. |last9=Wurzer |first9=M. |last10=Gerl |first10=M. |last11=Schnitzenbaumer |first11=M. |last12=Barth |first12=J. V. |last13=Libisch |first13=F. |last14=Lemell |first14=C. |last15=Burgdörfer |first15=J. |last16=Feulner |first16=P. |last17=Kienberger |first17=R. |display-authors=5 |journal=[[Nature (journal)|Nature]] |volume=561 |year=2018 |issue=7723 |pages=374–377 |doi=10.1038/s41586-018-0503-6|pmid=30232421 |url=https://mediatum.ub.tum.de/1579367 }}</ref> A broad consensus is emerging towards the fact that photoemission is not instantaneous and involves finite time.

The role of electric field in photoelectric effect has also been empirically studied and it was found that electromagnetic radiation with a specific orientation of electric field can excite electrons leading to enhanced emission in the Terahertz range.<ref name="Ritchie">{{cite journal |title=An in-plane photoelectric effect in two-dimensional electron systems for terahertz detection |journal=[[Science Advances]] |volume=8 |year=2022|last1=Michailow |first1=W.|last2=Ritchie |first2=D.|issue=15 |pages=eabi8398 | doi=10.1126/sciadv.abi8398 |pmid=35427162 |pmc=9012455 |arxiv=2011.04177 |bibcode=2022SciA....8I8398M }}</ref>