JP3672795B2 - Resistive shunt Josephson junction device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resistance shunt intrinsic Josephson junctions equipment using copper oxide high-temperature superconductor.
[0002]
[Prior art]
In recent years, various weakly coupled Josephson elements such as crystal grain boundaries and step edges using a copper oxide high-temperature superconductor have attracted attention because they can operate at a liquid nitrogen temperature (77 K). As weakly coupled Josephson elements, elements having various structures such as (1) bridge type, (2) point contact type, and (3) proximity effect type have been proposed. Since these elements have a very small capacitance floating in the weak coupling portion, there is no history in the current-voltage characteristics. A superconducting quantum interference device is composed of a superconductor closed circuit including a Josephson device and is used as an ultrasensitive magnetic sensor.
[0003]
[Problems to be solved by the invention]
However, as a conventional Josephson element using a copper oxide high-temperature superconductor, a resistance element (shunt resistor) that shunts a current flowing through its intrinsic Josephson junction (IJJ) is built in and used. There is nothing to do.
[0004]
The present invention is, in view of the above situation, the resistance element for shunting the current flowing through the intrinsic Josephson junctions of copper oxide high-temperature superconductor (shunt resistance) is built, a resistor shunt intrinsic Josephson junctions equipment that use them The purpose is to provide.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
[ 1 ] In a resistance shunt intrinsic Josephson junction device, a copper oxide high-temperature superconductor having a protrusion, an insulating material formed on a side of the protrusion of the copper oxide high-temperature superconductor, and the insulating material And a shunt resistor material formed so as to bridge the current, and a current is applied from the upper surface of the protrusion, and the current is derived from the copper oxide high-temperature superconductor.
[0006]
[2] The resistance shunt intrinsic Josephson junction device described in [1] Symbol mounting, the copper oxide high-temperature superconductor, Bi-Sr-Ca-Cu -O (BSCCO), Tl-Ba-Ca-Cu-O It is a single crystal or a thin film of (TBCCO) or oxygen-deficient Y-Ba-Cu-O (YBCO).
[0007]
[ 3 ] The super-radiation electromagnetic wave oscillator is configured by adding the voltage-frequency conversion function to the shunt resistance of the Josephson junction device inherent in the resistance shunt described in [1] as a high-frequency coupling circuit.
[0008]
[ 4 ] Josephson D / A conversion by biasing a specific number of junctions of the resistance shunt intrinsic Josephson junction device according to [1] above with a direct current and a micro frequency, and obtaining a quantum voltage by a primary Shapiro step. It constitutes a container.
[0009]
[ 5 ] The resistance shunt-specific Josephson junction device according to [1] is characterized in that the shunt resistance is made of a metal material, and a frequency mixer is provided that performs mixing at different frequencies.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0011]
A feature of the present invention is to use a resistance element (shunt resistor) that shunts a current flowing through an intrinsic Josephson junction (IJJ) of a copper oxide high-temperature superconductor. The IJJ having this new structure is named as a resistance shunt intrinsic Josephson junction (RS-IJJ) device.
[0012]
FIG. 1 is a configuration diagram of a resistance shunt-specific Josephson junction device showing a first embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of the resistance shunt-specific Josephson junction device.
[0013]
In these figures, 1 is Bi-Sr-Ca-Cu-O (BSCCO) on which the protrusion is formed, 2 is an Au electrode formed on the upper surface of the protrusion of the BSCCO1, and 3 is the protrusion of the BSCCO1. It is a shunt resistor formed on both sides. The shunt resistor 3 is made of a metal or a semiconductor that is equal to or lower than the normal conduction resistance of IJJ.
[0014]
When the BSCCO 1 is grounded and the current I is supplied from the Au electrode 2, shunt resistors Rc and Rs are formed in parallel with the Josephson junctions J ⁽¹⁾ ... J ⁽ⁱ⁾ . , Shunt current.
[0015]
FIG. 3 is a configuration diagram of a resistance shunt-specific Josephson junction device showing a second embodiment of the present invention, and FIG. 4 is an equivalent circuit diagram of the resistance shunt-specific Josephson junction device.
[0016]
In these figures, 11 is Bi-Sr-Ca-Cu-O (BSCCO) on which a protrusion is formed, 12 is an Au electrode formed on the upper surface of the protrusion of BSCCO 11 , and 13 is a protrusion of BSCCO 11 . Insulating materials 14 formed on both sides of the insulating material 13 are shunt resistors formed so as to bridge the insulating materials 13. The shunt resistor 14 is made of a metal or a semiconductor that is equal to or lower than the normal conduction resistance of IJJ.
[0017]
When the BSCCO 11 is grounded and the current I is supplied from the Au electrode 12, as shown in FIG. 4, a shunt resistor Rs is formed in parallel with a series circuit of Josephson junctions J ⁽¹⁾ ... J ⁽ⁱ⁾ . Shunt current.
[0018]
The BSCCO 11 can be replaced with another copper oxide superconductor. The upper Au electrode 12 can be replaced with another metal or a conventional superconductor. The shunt material can be a metal or a semiconductor. If a metal is used for shunting, the contact resistance (R _C ) becomes dominant as the shunt resistance, and the resistance of the metal can be replaced by a zero resistance wiring shown by the dotted line in FIG.
[0019]
Since it is configured as described above, the following improvement in characteristics is achieved as compared with the conventional IJJ.
[0020]
(A) As shown in FIGS. 1 and 2, RS-IJJ has a small hysteresis characteristic and a low voltage jump due to the shunt resistance. Therefore, since a stable voltage state in the millivolt region can be maintained, it is easy to obtain a phase lock between the externally applied centimeter wave, millimeter wave, and submillimeter wave electromagnetic waves and the internal Josephson oscillation. is there.
[0021]
(B) As shown in FIGS. 3 and 4, the shunt resistor enhances high-frequency electromagnetic coupling between the junctions in the laminated junction. As shown in FIG. 5, the Josephson voltage V ⁽¹⁾ ... V ⁽ⁱ⁾ ... Vibration of each junction induces a current Ie having the same frequency in the coupling circuit Rs (shunt resistor) and all the junctions J.
[0022]
This current can lock the phase of all junctions. Such an electromagnetic interaction is due to a high-frequency current (near the Josephson frequency), which is so-called high-frequency electromagnetic coupling. By obtaining this, the shunting impedance should be on the order of the junction impedance at the junction's Josephson frequency.
[0023]
(C) Since this shunt structure does not increase the effective magnetic penetration depth of IJJ, a high critical current can be maintained even in a high static magnetic field (˜1 Tesla). Therefore, RS-IJJ is very promising as a detector that operates in a high magnetic field.
[0024]
According to the present invention, the following applications are expected based on the above characteristics.
[0025]
[A] Superradiant electromagnetic wave oscillator A Josephson junction device can generally be regarded as a voltage-frequency converter. When a DC voltage V is applied to the junction, the Josephson current oscillates at a frequency f = K _J V (K _J = 483597.9 GHz / V; Josephson constant). However, the electromagnetic radiation output from one junction is relatively small. Since RS-IJJ can make the phase of each junction in-phase by a high-frequency coupling circuit (shunt resistor), it is considered that a super-radiation state in which an output proportional to N ² is exhibited appears. Here, N is the number of junctions in the laminated structure. Such an oscillator is suitable for many applications, such as a local oscillator in a SIS detector.
[0026]
[B] High-Accuracy Josephson D / A Converter FIG. 6 is a schematic diagram of a Josephson D / A converter composed of RS-IJJ according to the present invention.
[0027]
In this figure, × Josephson junctions, R _s is a shunt resistor, when the digital input bias current (binary 000 ... 001010) is applied, the analog output voltage _{V a- out (0 + 2 ×} V 0 + 0 + 8 × V ₀ + 0 = 10V ₀ ) can be obtained. The element corresponding to each bit is a stack having a specific number of junctions, 15 is a DC power source, and 16 is a bias resistor.
[0028]
Due to the uniformity of each IJJ in the laminated junction and its close-packed structure, the microwave response is considered to be the same for every junction. As shown in FIG. 6 (a), by biasing a specific number (N) of junctions with a direct current _Ib and microwaves, as shown in FIG. 6 (b), a primary Shapiro step (1 ^st Shapiro step) is performed. In step), the quantum voltage V = Nf _rf / K _J is obtained.
[0029]
Here, f _rf is the microwave frequency. Since the frequency of the microwave can be controlled very well, a high-precision D / A converter can be manufactured by adding the voltages generated in different N junction arrays.
[0030]
[C] the frequency mixer I _C R _N product also becomes few millivolts, the characteristic frequency (upper limit frequency bonding can operate) reaches up to several terahertz. Here, I _C is a critical current and _RN is a normal resistance. In addition, since there is a stable low voltage region in the current-voltage characteristics, it is very useful to use RS-IJJ to perform mixing experiments for spectroscopic measurement and frequency measurement.
[0031]
FIG. 7 is a configuration diagram of a frequency mixer using a resistance shunt intrinsic Josephson junction according to the present invention.
[0032]
In this figure, 21 is a BSCCO on which a projection is formed, 22 is an Au electrode formed on the upper surface of the projection of the BSCCO 21, and 23 is Au as a shunt resistance material formed on both sides of the projection of the BSCCO 21. is there.
[0033]
A current to which a dc bias is applied is applied from the Au electrode 22, the BSCCO 21 is grounded, and an amplifier 25 is connected to the current source via a coupling capacitor 24.
[0034]
Therefore, when the frequencies f _S and f _LO act on this frequency mixer, the frequencies f _S and f _LO are mixed, and f _IF = | f _S −Nf _LO | can be obtained.
[0035]
That is, because of the intermediate frequency (f _IF ) equal to the difference between the signal frequency (f _S ) of the local vibrator (f _LO ) and the Nth harmonic, the output level at this intermediate frequency (f _IF ) is the Josephson junction. It strongly depends on the characteristics of.
[0036]
Thus, harmonic synthesis can be a useful probe for investigating the response to high frequency irradiation or luminescence present in IJJ. On the other hand, the frequency stability and measurement accuracy at low frequencies (f _IF , f _LO ) can be shifted to a very high frequency (f _S ). Harmonic synthesis can be used, for example, to make a phase-locked vibrator.
[0037]
With the new resistively shunted IJJ of the present invention, it is possible to obtain very high IF output.
[0038]
In addition, although the example using BSCCO was described as a copper oxide high temperature superconductor which comprises RS-IJJ, Tl-Ba-Ca-Cu-O (TBCCO) or oxygen-deficient Y-Ba-Cu-O ( YBCO) single crystal or thin film may be used.
[0039]
[D] On-chip detector In order to observe the plasma oscillation in the high-temperature superconductor, a detector must be fabricated on the chip of IJJ and other elements.
[0040]
8 and 9 are examples using the RS-IJJ to detect magnetic flux flow oscillation elongated in intrinsic Josephson junctions fabricated on BSCCO single crystal.
[0041]
The main difference between the structures of FIGS. 8 and 9 is the method of coupling microwave radiation.
[0042]
The coupling of microwave radiation in FIG. 8 is not a direct coupling.
[0043]
BSCCO other elements having an elongated intrinsic Josephson junction consisting of a single crystal (FFO: Flux Flow Oscillator: flux flow vibrator) 3 2 or these emission proceeds to the free space, the detector comprising a RS-IJJ 3 Combine with 3.
[0044]
8, 31 chips, other elements having 32 thereof formed on the chip 31, elongated intrinsic Josephson junction consisting of BSCCO single crystal (FFO: Flux Flow Oscillator: flux flow agitator) Reference numeral 33 denotes a detector formed of RS-IJJ that is formed on the chip 31 and detects magnetic flux flow vibration (plasma vibration) 35 in the intrinsic Josephson junction. A shunt resistor 34 is provided on a side surface of the detector 33. It is formed.
[0045]
Therefore, the current Ib is applied to the FFO 32, the chip 31 is grounded, and the voltage V corresponding to the current Ib is obtained from the detector 33.
[0046]
The bonds in FIG. 9 are direct bonds. The reason is that the superconducting CuO ₂ (copper dioxide) layer is much thinner than the penetration depth in London. The phase change of IJJ in the chip 41 part has a great influence on the phase change of RS-IJJ in the detector 43 part made of RS-IJJ.
[0047]
Also in the case of FIG. 9, 41 chips, 42 formed on the chip 41, other elements having an elongated intrinsic Josephson junction consisting of BSCCO single crystal (FFO), 43 is the FFO42 It is a detector made of RS-IJJ for detecting magnetic flux flow vibration (plasma vibration) 45 in the upper part of one end and detecting the intrinsic Josephson junction. A shunt resistor 44 is formed on the side surface of the detector 43. The
[0048]
Therefore, the current Ib is applied to the FFO 42, the chip 41 is grounded, and the voltage V corresponding to the current Ib is obtained from the detector 43.
[0049]
Therefore, according to the on-chip detector, capable of detecting a magnetic flux flow oscillation in the intrinsic Josephson junction elongated on a single crystal (plasma oscillation).
[0050]
The present invention is not limited to the above-described embodiments, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.
[0051]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0052]
(A) A resistance element (shunt resistor) that shunts the current flowing in the intrinsic Josephson junction of a copper oxide high temperature superconductor is built in, and a resistance shunt intrinsic Josephson junction device for a copper oxide high temperature superconductor is provided. can do.
[0053]
(B) The super-radiation electromagnetic wave oscillator can be obtained by using the shunt resistance of the Josephson junction device as a high-frequency coupling circuit and adding a voltage-frequency conversion function.
[0054]
(C) A high-precision Josephson D / A converter can be obtained by biasing a specific number of junctions of a Josephson junction device with a direct current and a micro frequency and obtaining a quantum voltage by a primary Shapiro step. .
[0055]
(D) It is possible to obtain a frequency mixer that performs mixing at different frequencies by making the shunt resistance of the Josephson bonding device a metal material.
[0056]
(E) An on-chip detector capable of accurately detecting magnetic flux flow vibration can be obtained.
[0057]
As described above, a wide range of applications such as a superradiant electromagnetic wave oscillator, a highly accurate Josephson D / A converter, a frequency mixer, and an on-chip detector are possible.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a resistance shunt-specific Josephson junction device showing a first embodiment of the present invention.
FIG. 2 is an equivalent circuit diagram of the resistance shunt intrinsic Josephson junction device showing the first embodiment of the present invention.
FIG. 3 is a configuration diagram of a resistance shunt intrinsic Josephson junction device showing a second embodiment of the present invention.
FIG. 4 is an equivalent circuit diagram of a resistance shunt intrinsic Josephson junction device showing a second embodiment of the present invention.
[5] Josephson voltage oscillation of the bonding according to the present invention is to induce a current of the same frequency in all joined to the coupling circuit (shunt resistor), the current will be described to lock the phases of all the joint FIG.
FIG. 6 is a schematic diagram of a Josephson D / A converter composed of RS-IJJ according to the present invention.
FIG. 7 is a configuration diagram of a frequency mixer using a resistance shunt intrinsic Josephson junction according to the present invention.
Is a Figure 8 is a configuration diagram of a magnetic flux flow oscillation of the detection device in the present invention the intrinsic Josephson junction BSCCO single crystal on a fabricated elongated according to (1).
A 9 is a configuration diagram of a magnetic flux flow oscillation detection device of the elongated in intrinsic Josephson junctions fabricated on BSCCO single crystal according to the present invention (Part 2).
[Explanation of symbols]
1,11,21 Bi-Sr-Ca-Cu-O (BSCCO) with protrusions formed
2,12,22 Au electrode 3,14,34,44 Shunt resistor 13 Insulating material
15 DC power supply
16 bias resistor 23 Shunt resistor (Au)
24 coupling capacitor 25 amplifier 31, 41 chip 32, 42 FFO (other elements)
33, 43 Detector 35, 45 Magnetic flux flow vibration (plasma vibration)

Claims (5)

(A) a copper oxide high-temperature superconductor having a protrusion formed thereon;
(B) an insulating material formed on the side of the protrusion of the copper oxide high-temperature superconductor;
(C) providing a shunt resistance material formed to bridge the insulating material;
(D) A resistance shunt-specific Josephson junction device, wherein a current is applied from an upper surface portion of the protrusion and the current is derived from the copper oxide high-temperature superconductor. In resistance shunt intrinsic Josephson junction device according to claim 1 Symbol placement, the copper oxide high-temperature superconductor, Bi-Sr-Ca-Cu -O (BSCCO), Tl-Ba-Ca-Cu-O (TBCCO) or A resistance shunt intrinsic Josephson junction device characterized by being a single crystal or a thin film of oxygen-deficient Y-Ba-Cu-O (YBCO).   The resistance shunt-specific Josephson junction device according to claim 1, wherein the shunt resistance of the resistance shunt-specific Josephson junction device is a high-frequency coupling circuit, and a super-radiation electromagnetic wave oscillator is configured by adding a voltage-frequency conversion function. .   A Josephson D / A converter is constructed by biasing a certain number of junctions of a resistive shunt intrinsic Josephson junction device according to claim 1 with a direct current and a micro frequency and obtaining a quantum voltage in a first-order Shapiro step. A resistance shunt-specific Josephson junction device.   A resistance shunt-specific Josephson bonding apparatus according to claim 1, wherein the resistance shunt-specific Josephson bonding apparatus comprises a frequency mixer that performs mixing at different frequencies by forming the shunt resistance of a metal material.

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