Use of low charge, in the pC range, has been recently proposed for enabling GeV-class beams to be compressed to the hundreds of attosecond level [1]. Further, these beams are pre- dicted to have very low normalized transverse emittance ϵ$_{n}$ , and thus unprecedented bright- ness. This proposal was generated in the context of planning future X-ray self-amplified spontaneous emission free-electron lasers (SASE FELs [2]). The scheme addresses two chal- lenges in the X-ray SASE FEL: it breaches the fs frontier in X-ray pulse length, and it allows single spike SASE FEL performance. Both properties permit exploitation of the rev- olutionary aspects of coherent X-ray FEL light, as one may resolve properties of atomic and molecular systems at the spatial and temporal scales relevant to electronic motion [3]. With the advantages of low charge operation well appreciated, initial experimental work has been undertaken at the Stanford Linear Coherent Light Source (LCLS) recently. In these initial tests, 20 pC beams were compressed to rms duration σ$_{t}$ ≃ 2 fs, while achieving emittances ϵ$_{n,x}$$_{(}$$_{y}$$_{)}$ = 0 . 14(0 . 4) mm-mrad at an energy U$_{b}$ = 14 GeV. This beam, having very high current I and low emittance − and thus high brightness, B = 2 I/ϵ$_{n,x}$ϵ$_{n,y}$ − is predicted to produce nm-wavelength FEL pulses in the single-spike regime [4]. Beams with such short duration can produce coherent electromagnetic excitations with frequency components up to ω$_{max}$ ≃ σ − 1 t . Here we are interested in plasma wakefield exci- tations, which produce a radiated field amplitude E that scales as E ≃ N$_{b}$ω 2 max ≃ N$_{b}$/σ 2 t , where N$_{b}$ is the number of particles in the beam. To maximize the wake amplitude, one utilizes, ω$_{max}$ = ω$_{p}$ , giving the wake optimization condition ω$_{p}$σ$_{t}$ ≃ 1. This scaling has been investigated experimentally [5, 6], theoretically and computationally [7], and its applicabil- ity even in the nonlinear blowout regime [8] has been established. In fact, operation in the blowout regime is desired, as in this the plasma electrons are ejected from the beam channel, producing acceleration dependent only on longitudinal position ξ = z − v$_{b}$t in the beam chan- nel, where v$_{b}$ ≃ c is the beam z -directed velocity. Further, the nominally uniform ion density in the electron-free region gives focusing linearly dependent on radial position r relative to the beam ( z ) axis. Thus the forces acting on the beam may produce high quality beams with the phase space density demanded by advanced applications in high-energy physics and light sources. The purpose of this Letter is to explore the physics implications of using this new class of beam in the context of a plasma wakefield acceleration (PWFA) experiment, showing that it may yield fields of unprecedented amplitude and time scale, opening unique and compelling opportunities in plasma, accelerator, and atomic physics. We proceed by 2