Resistively Shunted Josephson Junction Research Articles

Reply to “Comment on ‘Absence of a Dissipative Quantum Phase Transition in Josephson Junctions”’

In their Comment [P. Hakonen and E. B. Sonin, preceding comment, Phys. Rev. X 11, 018001 (2021)], Hakonen and Sonin (HS) object to our conclusion on the absence of a dissipation-induced superconducting-to-insulating quantum phase transition (DQPT) in resistively shunted Josephson junctions (RSJJs) originally predicted by Schmid and Bulgadaev (SB). Their objections are based on the account they make of a theory explaining the DQPT in terms of Bloch bands which was developed in the 1980s and early 1990s. In this Reply, we point to several issues in the Comment which undermine the objections HS formulate against our work.

Probing the minigap in topological insulator-based Josephson junctions under radio frequency irradiation**Project supported by the National Basic Research Program of China (Grant Nos. 2016YFA0300601, 2017YFA0304700, and 2015CB921402), the National Natural Science Foundation China (Grant Nos. 11527806, 91221203, 11174357, 91421303, and 11774405), and the Strategic Priority Research Program B of the Chinese Academy of Sciences (Grant Nos. XDB07010100 and XDB28000000), and

Recently, a contact-resistance-measurement method was developed to detect the minigap, hence the Andreev bound states (ABSs), in Josephson junctions constructed on the surface of three-dimensional topological insulators (3D TIs). In this work, we further generalize that method to the circumstance with radio frequency (rf) irradiation. We find that with the increase of the rf power, the measured minigap becomes broadened and extends to higher energies in a way similar to the rf power dependence of the outer border of the Shapiro step region. We show that the corresponding data of contact resistance under rf irradiation can be well interpreted by using the resistively shunted Josephson junction (RSJ) model and the Blonder–Tinkham–Klapwijk (BTK) theory. Our findings could be useful when using the contact-resistance-measurement method to study the Majorana-related physics in topological insulator-based Josephson junctions under rf irradiation.

Asymmetric frequency conversion in nonlinear systems driven by a biharmonic pump.

A novel mechanism of asymmetric frequency conversion is investigated in nonlinear dispersive devices driven parametrically with a biharmonic pump. When the relative phase between the first and second harmonics combined in a two-tone pump is appropriately tuned, nonreciprocal frequency conversion, either upward or downward, can occur. Full directionality and efficiency of the conversion process is possible, provided that the distribution of pump power over the harmonics is set correctly. While this asymmetric conversion effect is generic, we describe its practical realization in a model system consisting of a current-biased, resistively shunted Josephson junction. Here, the multiharmonic Josephson oscillations, generated internally from the static current bias, provide the pump drive.

An Interlayer Magnetoresistance Peak Effect below the Superconducting Transition Temperature in Et2Me2P[Pd(dmit)2

The longitudinal magnetoresistance of a two-dimensional superconductor, $$\beta'- Et_{2}Me_{2}P[Pd(dmit)_{2}]_{2} (dmit=C_{3}S^{2-}_{5})$$ under hydrostatic pressure was measured at low temperatures with the field applied perpendicular to the conducting layers. At 0.58 GPa, the field-dependent isothermal interlayer resistance $$R_{\perp}(H)$$ exhibited a peak below the superconducting transition temperature TC. This peak effect can be explained by a model of resistively-shunted Josephson-Junctions. The peak is strongly suppressed at a higher pressure, 0.71 GPa.

Smooth NdBa2Cu3O7−δ thin films and ramp Josephson junctions

We report on c-axis oriented NdBa2Cu3O7−δ (NBCO) superconducting thin films grown on SrTiO3 substrates using pulsed laser deposition. The transition temperature of these NBCO films was around 89.5 K and the root mean square (RMS) surface roughness for 150 nm thick films was 0.75 nm. Insulating layers of of PrBa2Cu3O7−δ/SrTiO3/PrBa2Cu3O7−δ grown on top of the NBCO superconducting films result in superconductor/insulator multilayers of about 400 nm in total thickness and an RMS surface roughness of 2.4 nm. Smooth ramps with angles of about 20° are patterned in the multilayers using a photoresist reflow process and Ar ion milling. 15-25 nm thick Ga-doped of PrBa2Cu3O7−δ barriers and NBCO counter electrodes are deposited on the ramp forming Josephson junctions. Current-voltage (I - V) curves of the obtained ramp Josephson junctions were studied at 4.2 K. Multiple Shapiro steps were observed when the junctions were irradiated at frequencies around 10 GHz. The amplitudes of these steps oscillate with microwave power in agreement with the resistively shunted Josephson junction (RSJ) model.

Efficient Simulation of Resistively Shunted Josephson Junctions

We present a cluster algorithm for resistively shunted Josephson junctions or similar physical systems, which dramatically improves sampling efficiency, and apply it to the superconductor-to-metal transition in a single junction. Measuring the temperature dependence of the zero bias resistance, we confirm that the critical point does not depend on the strength of the Josephson coupling. However, we find that the correlation exponents vary continuously along the phase boundary, indicating that the Schmid-Bulgadaev transition is a line of fixed points.

High-Tc ramp-type Josephson junctions on MgO substrates for terahertz applications

The authors successfully fabricated high-Tc ramp-type junctions with PrBa/sub 2/Cu/sub 3-x/Ga/sub x/O/sub 7-/spl delta// (PBCGO: x=0.1, 0.4) barriers on MgO substrates. The junctions showed resistively shunted Josephson junction (RSJ)-like I-V curves with thermally and voltage activated conductivity. The I/sub c/R/sub n/ products for these junctions scaled very well with the Ga-doping. Maximum response of the junctions for 100-GHz millimeter-wave irradiation could be observed up to 12 mV corresponding to 6 THz. Using far infrared laser radiation, we confirmed a terahertz (THz) response of these junctions. These results show promise for THz-wave applications of ramp-type Josephson junctions.

YBa/sub 2/Cu/sub 3/O/sub 7/(-x) step-edge junctions prepared on sapphire substrates with YSZ buffer layer

Electrical properties of YBa/sub 2/Cu/sub 3/O/sub 7-x/(YBCO) step-edge junctions were investigated. Steps of height approximately 90 nm were prepared on sapphire substrates by Ar milling. Step angles were adjusted by the angle of incidence of Ar ions. After vacuum deposition of the YSZ buffer layer (50 nm thick) an epitaxial YBCO film was grown by magnetron sputtering. Step edge junctions were prepared by wet etching. The current-voltage characteristics were of RSJ type, with I/sub c/R/sub n//spl ap/0.5 mV at 77 and Shapiro steps were observed up to 0.2 mV (at 9.2 GHz in the temperature range 4.2-80 K) and compared with the resistively shunted Josephson junction (RSJ) model including capacitance and noise.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Josephson behaviour and flux penetration effects in YBCO double tilt-angle step-edge junctions

YBCO thin-film step-edge junctions have been prepared whose characteristics show features corresponding to the two tilt-angle grain-boundary junctions formed at the step. The I-V characteristics of these junctions are fitted to high accuracy by a model consisting of two noisy resistively-shunted Josephson junctions. In applied magnetic fields up to a few hundred microtesla, both junction critical currents show reversible flux modulation, in one case indicating excellent uniformity of the critical current distribution along the step. In stronger magnetic fields, the junction critical current modulation shows evidence of flux penetration into the film, i.e. the mixed state. Taking demagnetising effects into account the lower critical field of YBCO at 77 K, /spl mu//sub 0/H/sub e1,e/, is found to be 12 mT. >

YBCO microwave grain boundary mixer using a SrTiO/sub 3/ bicrystal substrate

A microwave mixer was patterned on a microstrip transmission line of superconducting YBCO (YBa/sub 2/Cu/sub 3/O/sub 7-x/). The YBCO film was epitaxially laser deposited on a SrTiO/sub 3/ bicrystal substrate. A weak link was constructed by patterning a microbridge in the microstrip at the bicrystal boundary. Microwave signals at 9.000 GHz and 9.941 GHz were applied at the input of the microstrip line. An output intermediate frequency signal was observed at 941 MHz and was detected as the transmitted signal. The microbridge junction, which behaved as a resistively shunted Josephson junction (RSJ), was current biased slightly above the critical current I/sub c/. The mixer conversion loss was measured at the input and output ports of the device package. The mixing efficiency was determined at the device junction. This efficiency was compared with the calculated efficiency determined by numerical solution of the Josephson equation for the weak link junction. >

Comments on "Josephson effect gain and noise in SIS mixers" [with reply

For the original article see ibid., vol.40, no.5, p.820-6 (1992). The commenter points out that, in the above-titled paper by M.J. Wengler et al., no references published prior to 1982 are cited. As a result, no mention is made of a considerable body of relevant published work. The commenter discusses some of this earlier work. One of the authors, M.J. Wengler, replies that the earlier work all used point contact junctions with low capacitance and with nonhysteretic current-voltage (I-V) curves which fit the resistively shunted Josephson junction (RSJ) circuit model, whereas he and his coauthors considered planar SIS diodes with higher capacitance and with completely hysteretic I-Vs which are not even similar to the RSJ model predictions. He offers some further discussion of the ways in which their results are distinct from the earlier work. >

Dynamical Properties of Weakly Coupled Josephson Systems

ABSTRACTWe review recent work on the dynamical behavior of coupled resistively-shunted Josephson junctions, with emphasis on our own calculations. We present a model which allows for the inclusion of finite temperature, disorder, d.c. and a. c. applied currents, and applied magnetic fields. We discuss applications to (a) calculations of critical currents and IV characteristics; (b) harmonic generation and microwave absorption by finite clusters of Josephson junctions; (c) critical energies for vortex depinning; and (d) quantized voltage plateaus in arrays subjected to combined d.c. and a. c. currents. Possible connections to the behavior of granular high-temperature superconductors are briefly discussed.

Quantum-Noise Theory for the Resistively Shunted Josephson Junction

It is shown that the low-frequency spectral density of the voltage noise in a current-biased Josephson junction with critical current ${I}_{0}$, shunt resistance $R$, and small capacitance is $\frac{e{{I}_{0}}^{2}{R}^{3}}{\ensuremath{\pi}V}$ in the limit $\mathrm{eV}\ensuremath{\gg}{k}_{\mathrm{B}}T{(\frac{I}{{I}_{0}})}^{2}$ and $I&gt;{I}_{0}$, where $V$ is the voltage and $I$ is the current. The noise arises from zero-point current fluctuations in the shunt resistor. The rounding of the current-voltage characteristic caused by the quantum fluctuations and the effects of nonzero junction capacitance are calculated.