Superluminal geometrical resonances observed inBi2Sr2CaCu2O8+x

Abstract

We study Fiske steps in small Bi 2 Sr 2 CaCu 2 O 8+x mesa structures, containing only few stacked intrinsic Josephson junctions. Careful alignment of magnetic field prevents penetration of Abrikosov vortices and facilitates observation of a large variety of high quality geometrical resonances, including superluminal with velocities larger than the slowest velocity of electromagnetic waves. A small number of junctions limits the number of resonant modes and allows accurate identification of modes and velocities. It is shown that superluminal geometrical resonances can be excited by subluminal fluxon motion and that flux-flow itself becomes superluminal at high magnetic fields. We argue that observation of high-quality superluminal geometrical resonances is crucial for realization of the coherent flux-flow oscillator in the THz frequency range.

Persistent electrical doping of Bi2Sr2CaCu2OMotzkau1, Jacobs2, Katterwe3 et al. 2012Phys. Rev. B131100View full textAdd to dashboardCite

“…Indeed, the displacement field is given by D = Vε r /Nt, where ε r is the dielectric constant and t is the thickness of the insulating barrier between CuO bi-layers. The ratio t/ε r 0.1 nm was estimated from an analysis of Fiske (geometrical resonance) step voltages [31]. Therefore, the displacement field in intrinsic junctions is…”

“…SrO-2BiO-SrO in case of Bi-2212). This leads to a formation of atomic scale intrinsic tunnel junctions, and to an appearance of the intrinsic Josephson effect at T < T c [10,[28][29][30][31].…”

Linewidth dependence of coherent terahertz emission from Bi2Sr2CaCu2OLi1, Yuan2, Kinev3 et al. 2012Phys. Rev. B

“…Recent 3D simulations [39] based on the sine-Gordon equation and taking a hotspot into account yielded an asymmetric Fano shape in contrast to our experimental data. If ∆f of the high-bias THz emission signal were set by a cavity resonance, its quality factor Q = f /∆f would have to amount some 10 4 , which is more than unrealistic for an IJJ stack [28,38,43]. At least for small mesas, cavity resonances become overdamped for T > 60 K [43].…”

Observation of a subharmonic gap singularity in interlayer tunneling characteristics ofBi2Sr2CaCu2O8+δ

“…However, eI c R n /∆ rapidly decreases upon opening of the pseudogap in the underdoped state [13,14]. This may either * Electronic address: Vladimir.Krasnov@fysik.su.se indicate that interlayer tunneling becomes progressively more incoherent with decreasing doping [13], or that the Fermi surface is reconstructed by the pseudogap [14].Intrinsic Josephson junctions are characterized by low dissipation [15]. This is often taken as evidence for Superconductor-Insulator-Superconductor (SIS) structure of Bi-2212, in which S are superconducting CuO 2 -Ca-CuO 2 bilayers and I is the insulating SrO-2BiO-SrO layer.…”

“…Intrinsic Josephson junctions are characterized by low dissipation [15]. This is often taken as evidence for Superconductor-Insulator-Superconductor (SIS) structure of Bi-2212, in which S are superconducting CuO 2 -Ca-CuO 2 bilayers and I is the insulating SrO-2BiO-SrO layer.…”