Nearly every wavelength from dc to x-rays significantly benefits today's society with a notable exception: the THz or
sub-millimeter band. Applications in this range are widespread, penetrating fields ranging from national security to
medicine, but remain largely under-utilized due to the difficulty of creating, manipulating, and detecting this type of
radiation. Our research focus is THz source development using superconductive Josephson junctions to potentially
address the lack of compact, efficient, and tunable source of continuous THz radiation. We review relevant applications
for such a source and report an optimized design of a miniature THz emitter using single crystal intrinsic Josephson
junctions.
We consider two representative problems that deal with the
fluctuator-induced decoherence from two very different
perspectives-microscopic and macroscopic. In the first part, we consider an individual two-level system
inside a Josephson junction shunted by a resistor. If the TLS modulates the Josephson energy and/or is optically
active, it can be Rabi driven by the Josephson oscillation. The Rabi oscillations, in turn, translate into oscillations
of current and voltage which can be detected in noise measurements. This effect provides an option to
fully characterize the TLS inside Josephson junction and to find the TLS's contribution to the decoherence when
the junction is used as a qubit. In the second part, we study the contribution of an ensemble of non-stationary
glassy charge fluctuators on qubit decoherence. Low-temperature dynamics of insulating glasses is dominated
by a macroscopic concentration of tunneling two-level systems. Due to exponentially broad distribution of their
tunneling rates and the finite experimental manipulation timescales, some of the fluctuators are temporarily
stuck in high-energy non-thermal states. We find that at low enough temperatures, non-stationary contribution
due to these slow non-thermal fluctuators can dominate the stationary (thermal) one, and discuss how this effect
can be minimized.
We consider the Josephson vortex flow in layered superconductors in the presence of the transport DC current perpendicular to the layers and high magnetic field parallel to the layers. Moving vortex lattice induces the radiation from the edge of the crystal into the dielectric. We derive radiation power for moving rectangular and triangular lattice. We estimate corresponding radiation power for Bi-based cuprate superconductor when the magnetic field of order of one tesla is applied and the radiation frequency is in THz interval. We show qualitatively that radiation power for lattice disordered along the c-axis is weaker than that for regular lattice. We estimate the heat flow which in cuprate crystals is determined mainly by the nodal quasiparticles.
Josephson plasma resonance has been introduced recently as a powerful tool to probe interlayer Josephson coupling in different regions of vortex phase diagram. In the pancake liquid plasma resonance frequency (omega) p(B,T) as function of the magnetic field B was obtained previously using the high temperature expansion. We further develop this approach and derive a general relation connecting (omega) p(B) with the density correlation function of pancake liquid. The relation provides unique opportunity to extract quantitative information on the c-axis correlations of pancake liquid in crystals with weak and strong pinning from the dependence of plasma resonance on the ab-component of magnetic field at fixed c component. We discuss c-axis correlations in crystals with weak disorder and crystals with columnar defects produced by irradiation.
The effect of quantum fluctuations of vortices on the low temperature specific heat and reversible magnetization in the mixed state in highly anisotropic layered superconductors is discussed. For reversible magnetization, M, the change of slope in the dependence of M vs InB, observed in Bi(2:2:1:2) single crystals, is explained. In the mean field approach this slope should be almost B independent. We show that for magnetization quantum fluctuations are important at all temperatures except in a narrow region near Tc. The specific heat due to the vortex fluctuation contribution is predicted to be linear in T at low T and to increase logarithmically with B.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.