Reentrant quantum phase transitions in two capacitively coupled Josephson arrays in perpendicular magnetic fields

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2008-02, Vol.77 (6), Article 064513
• Main Authors: Ramirez-Santiago, Guillermo, Jose, Jorge V., Department of Physics, Fronczak Hall, University at Buffalo, State University of New York, Buffalo, New York 14260-1500
• Format: Article
• Language: English
• Subjects: CAPACITANCE; COMPETITION; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COUPLING; DUALITY; EXCITATION; FLUCTUATIONS; GAUGE INVARIANCE; INTERACTIONS; JOSEPHSON EFFECT; JOSEPHSON JUNCTIONS; MAGNETIC FIELDS; MONTE CARLO METHOD; PERMITTIVITY; PHASE DIAGRAMS; PHASE TRANSFORMATIONS; SEMICLASSICAL APPROXIMATION; TEMPERATURE DEPENDENCE; VORTICES
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.77.064513

We have studied the phase diagram structure of two capacitively coupled Josephson junction arrays as a function of their charging energy E{sub c}, Josephson coupling energy E{sub J}, and a homogeneous perpendicular magnetic field. The arrays are coupled via a site interaction capacitance, C{sub int}=C{sub inter}/C{sub m}, with C{sub inter} as the interlayer mutual capacitance and C{sub m} as the intralayer mutual capacitance defined as the nearest neighbor grain mutual capacitance. The parameter that measures the competition between thermal and quantum fluctuations in the ith array (i=1,2) is {alpha}{sub i}{identical_to}E{sub c{sub i}}/E{sub J{sub i}}. The phase structure of the system is dominated by the thermally induced and magnetically induced vortices as well as intergrain charge induced excitations. We have studied the capacitively coupled array behavior when one of them is in the vortex dominated regime, and the other in the quantum charge dominated regime. We determined the different possible phase boundaries by carrying out extensive quantum path integral Monte Carlo calculations of the helicity modulus {upsilon}{sub 1,2}({alpha},f) and the inverse dielectric constant {epsilon}{sub 1,2}{sup -1}({alpha},f) for each array as a function of temperature, interlayer capacitance C{sub int}, quantum parameter {alpha}, and frustration values f{identical_to}({phi}/{phi}{sub 0})=1/2 and f=1/3. Here, {phi} is the total flux in a plaquette and {phi}{sub 0} is the quantum of flux. We found an intermediate temperature range when array 1 is in the semiclassical regime ({alpha}{sub 1}=0.5) and array 2 is in the quantum regime with 1.25{2.0, the quantum array only exhibits an insulating phase, while the semiclassical array shows a superconducting behavio