Physics and performance of high temperature superconducting vortex flow transistors

Gross, Rudolf; Gerdemann, R.; Alff, Lambert; Beck, A.; Froehlich, O. M.; Koelle, D.; Marx, Achim

doi:10.1016/0964-1807(96)85904-7

Cited by 24 publications

(25 citation statements)

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“…Interestingly, a switching behaviour that is due to strong self-field effects with very high values of g associated with it have been predicted theoretically for JVFTs with an asymmetric bias current distribution. 1,8 However, it has never been observed experimentally. In our case the switching behaviour has a different nature, as explained below.…”

mentioning

confidence: 88%

“…4(a) and 4(b)) where the degree of I c (I ctrl ) asymmetry and g max both gradually increase as we decrease T. A similar rapid transition with increasing b L (decreasing temperature) from a symmetric I c (I ctrl ) to an asymmetric one was predicted to occur in discrete JVFTs with an asymmetric current bias distribution. 1,7,8 Considering the increase in I c due to a change in temperature from 89 K to 77 K an average value for b L of 1.9 can be estimated at 77 K which is close to the designed value of 1.5. In contrast to I c (I ctrl ) curves, V(I ctrl ) curves are almost symmetric at all temperatures.…”

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confidence: 92%

“…[5][6][7] A high performance JVFT for practical applications should have a high current gain, g ¼ @I c /@I ctrl (where I c is the device critical current and I ctrl is the control-gate current), a large dynamic range (the range of I ctrl over which a high g can be achieved), small vortex transit times to allow high frequency operation and a relatively large transresistance, r m ¼ @V/@I ctrl . Several JVFT designs have been proposed so far which differ in (i) current bias distribution (symmetric overlap 1,3 or asymmetric inline 5-7 ), or (ii) gate line geometry (different gate design 4 or different gate line relative orientation with respect to the junctions 6 ). It has been shown 1,3 that discrete JVTFs with an asymmetric current bias distribution have much larger current gains than discrete JVFTs with a symmetric one.…”

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confidence: 99%

“…1,2 There are two types of JVFTs: ones that are based on a single long Josephson junction (JJ) 3,4 or JVFTs based on arrays of JJs. [5][6][7] A high performance JVFT for practical applications should have a high current gain, g ¼ @I c /@I ctrl (where I c is the device critical current and I ctrl is the control-gate current), a large dynamic range (the range of I ctrl over which a high g can be achieved), small vortex transit times to allow high frequency operation and a relatively large transresistance, r m ¼ @V/@I ctrl .…”

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confidence: 99%

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Parallel array of YBa2Cu3O7−δ superconducting Josephson vortex-flow transistors with high current gains

Chesca

John

Kemp

et al. 2013

Applied Physics Letters

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We have developed a Josephson vortex-flow transistor based on a parallel array of 440 YBa2Cu3O7−δ bicrystal grain boundary Josephson junctions. The array's critical current Ic was measured as a function of the control current Ictrl through a control line that is inductively coupled to the array. The device has a highly asymmetric Ic(Ictrl) curve with several regions where a switching behaviour is observed characterized by a maximum current gain gmax = ∂Ic/∂Ictrl of 19 and a significant dynamic range of 20 μA at 77 K. In the range 4.7–92 K gmax versus temperature is non-monotonic with a maximum recorded at 77 K.

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confidence: 88%

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confidence: 92%

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confidence: 99%

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confidence: 99%

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Parallel array of YBa2Cu3O7−δ superconducting Josephson vortex-flow transistors with high current gains

Chesca

John

Kemp

et al. 2013

Applied Physics Letters

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“…When damping is low flux flow dominates PAJJ's dynamics and they can be used as microwave generators [7][8] or superconducting transistors [9][10] [6]. All PAJJs investigated so far have been operated in either a flux-flow dominated regime or behaved as flux-interferometers.…”

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confidence: 99%

Dual flux-to-voltage response of YBa₂Cu₃O_7−δasymmetric parallel arrays of Josephson junctions

Chesca¹,

John²,

Mellor³

2014

Supercond. Sci. Technol.

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Fig. 4b and from 0.5 mA to 1mA (-1 mA to -0.5 mA) in Fig. 5a. Also, the amplitude of voltage modulation is considerable larger for negative currents relative to the positive currents. It is important to note that the families of V(I ctrl ) recorded for different current biases I plotted in Figs. 3b, 4b and 5b, they all lack inversion symmetry with respect to 0. This is because the PAJJ is not magnetically screened and therefore the presence of the earth magnetic field breaks such symmetry. Since the perpendicular component to the PAJJ planar structure of the earth magnetic field B normal is about 25 T it requires a significant shifting along the I ctrl current axis in order to compensate for the earth magnetic field and therefore recover the inversion symmetry. Indeed, the magnetic field corresponding to I ctrl =1.8mA (the current period of V(I ctrl ) curves) is about 2.4 T which is much smaller than B normal . The differences in the IVCs and V(I ctrl ) between the positive and the negative current biases are far less pronounced at temperatures below 60K. An example is shown in Fig. 6 for T=57.5 K. Similar characteristics have been measured at several other temperatures below 60K, namely, at 4.7K, 10K, and 30K.Indeed, the IVCs have a good degree of symmetry at these temperatures (see Fig.6a). Also, in this temperature range the V(I ctrl ) response becomes aperiodic (see Fig.6b) due to a significant suppression of the flux-flow modes due to a decrease in the dissipation coefficient 1/R N (or damping) with temperature (here R N is the normal resistance of the Josephson junction). A similar suppression of the flux-flow with decreasing T has been previously observed (both theoretically and experimentally) in PAJJs made of niobium low temperature superconductors [4,5].8 ConclusionIn conclusion, we have shown that an inductive asymmetric loop configuration within the array implemented in our PAJJ leads to a significant difference in the flux-flow for positive current biases relative to negative current biases and consequently to a corresponding different qualitative flux-to-voltage response. To achieve both an enhanced current amplification [11] and an enhanced microwave power generation [12] a PAJJ has to be operated in a regime of enhanced flux-flow, i.e., it should be biased with a positive current.The degree of asymmetry of our design can be further extended to enhance the contrast in the directional flux-flow and to improve PAJJs performances in these applications.

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Passive high-temperature superconducting microwave devices

Springer Tracts in Modern Physics

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Physics and performance of high temperature superconducting vortex flow transistors

Cited by 24 publications

References 85 publications

Parallel array of YBa2Cu3O7−δ superconducting Josephson vortex-flow transistors with high current gains

Parallel array of YBa2Cu3O7−δ superconducting Josephson vortex-flow transistors with high current gains

Dual flux-to-voltage response of YBa₂Cu₃O_7−δasymmetric parallel arrays of Josephson junctions

Passive high-temperature superconducting microwave devices

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Physics and performance of high temperature superconducting vortex flow transistors

Cited by 24 publications

References 85 publications

Parallel array of YBa2Cu3O7−δ superconducting Josephson vortex-flow transistors with high current gains

Parallel array of YBa2Cu3O7−δ superconducting Josephson vortex-flow transistors with high current gains

Dual flux-to-voltage response of YBa2Cu3O7−δasymmetric parallel arrays of Josephson junctions

Passive high-temperature superconducting microwave devices

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Product

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Dual flux-to-voltage response of YBa₂Cu₃O_7−δasymmetric parallel arrays of Josephson junctions