Approaching Petavolts per meter plasmonics using structured semiconductors

Abstract

A new class of strongly excited plasmonic modes that open access to unprecedented Petavolts per meter electromagnetic fields promise wide-ranging, transformative impact. These modes are constituted by large amplitude oscillations of the ultradense, delocalized free electron Fermi gas which is inherent in conductive media. Here structured semiconductors with appropriate concentration of n-type dopant are introduced to tune the properties of the Fermi gas for matched excitation of an electrostatic, surface "crunch-in" plasmon using readily available electron beams of ten micron overall dimensions and hundreds of picoCoulomb charge launched inside a tube. Strong excitation made possible by matching results in relativistic oscillations of the Fermi electron gas and uncovers unique phenomena. Relativistically induced ballistic electron transport comes about due to relativistic multifold increase in the mean free path. Acquired ballistic transport also leads to unconventional heat deposition beyond the Ohm's law. This explains the absence of observed damage or solid-plasma formation in experiments on interaction of conductive samples with electron bunches shorter than $\rm 10^{-13} seconds$. Furthermore, relativistic momentum leads to copious tunneling of electron gas allowing it to traverse the surface and crunch inside the tube. Relativistic effects along with large, localized variation of Fermi gas density underlying these modes necessitate the kinetic approach coupled with particle-in-cell simulations. Experimental verification of acceleration and focusing of electron beams modeled here using tens of Gigavolts per meter fields excited in semiconductors with $\rm 10^{18}cm^{-3}$ free electron density will pave the way for Petavolts per meter plasmonics.