JP2002050931A - High frequency oscillator using copper oxide superconducting single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency oscillator of a copper oxide superconducting single crystal which operates at a frequency in the range of 100 GHz to several THz (1012 Hz) using a layered crystalline structure formed in a dimension of several micrometers. SOLUTION: A junction 13 of copper oxide superconducting single crystal with a layered structure is formed, and a strong magnetic field Bout is applied in parallel with the layers so that a magnetic flux quantum is generated in each of the layers, and the magnitude of the junction in the direction of the layers is made to be almost equal to the magnitude of the magnetic flux quantum in the direction of the layers then, a current Idc more than the critical current is fed into the layer of the junction in the direction perpendicular to it to generate a voltage, so that the magnetic flux quantum is moved rapidly in the direction of the layers to generate a high frequency electric field of 100 GHz to about 10 THz in the direction perpendicular to the layers. An electromagnetic wave resonator 10 electromagnetically coupled with the junction is provided, wherein an electromagnetic wave is excited in the electromagnetic resonator 10 by the high frequency electric field generated in the junction and is accumulated as energy, and is taken out for use when needed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency oscillator using a copper oxide superconducting single crystal.

[0002]

2. Description of the Related Art Information communication technology for processing a large amount of information and transmitting it at high speed is required to be more advanced. In order to transmit a large amount of information at a high speed, an electronic element operating at a high frequency and a transmission line are required. Currently, the upper limit of the frequency used for information communication technology is several tens of GHz (10 ¹⁰ H).
z) to 100 GHz (10 ¹¹ Hz).

[0003]

As described above, conventionally, the upper limit of the frequency used in the information communication technology is several tens of GHz (10 ¹⁰ Hz) to 100 GHz (10 ¹¹ H).
z), which was not technically satisfactory.

In view of the above situation, the present invention is to process a copper oxide superconducting single crystal having a layered crystal structure into a size of several micrometers, and to process it over 100 GHz to several THz (10 ¹² H).
An object is to provide a high-frequency oscillator using a copper oxide superconducting single crystal operating in z).

[0005]

In order to achieve the above object, the present invention provides: [1] A high-frequency oscillator using a copper oxide superconducting single crystal, wherein a copper oxide superconducting single crystal junction having a layered structure is formed. A strong magnetic field is applied in parallel to the layers to generate magnetic flux quanta in each layer so that the size of the junction in the layer direction and the size of the magnetic flux quanta in the layer direction are approximately the same, and are perpendicular to the layer of the junction. The magnetic flux quantum is caused to move at high speed in the layer direction to generate a voltage in a direction perpendicular to the direction of 100 GHz to about 10 THz to generate a voltage by flowing the current in the direction more than the critical current, and electromagnetically coupled to the junction. An electromagnetic wave resonator is provided, an electromagnetic wave is excited in the electromagnetic wave resonator by a high-frequency electric field generated during joining, stored as energy, and taken out to use as needed.

As described above, a THz band high frequency oscillator is manufactured by electromagnetically coupling a micron-sized junction using a copper oxide superconducting single crystal and a resonator.

[0007]

Embodiments of the present invention will be described below in detail.

FIG. 1 shows an embodiment of the present invention, Bi ₂ Sr _2.
FIG. 2 is a view showing a crystal structure of a copper oxide superconducting single crystal (hereinafter, referred to as Bi2212) having a chemical composition of Ca ₁ Cu ₂ O _y and IV characteristics of a junction thereof. FIG. 2 is a focused ion beam processing showing an embodiment of the present invention. -Temperature superconducting Bi2212 produced by
FIG. 3 is a characteristic diagram of a current I _C versus a magnetic field B at a junction of a copper oxide superconducting single crystal showing an embodiment of the present invention, and FIG. 4 is a schematic diagram of a row of magnetic flux quanta in the junction. 5 is an explanatory view of a high-frequency THz oscillator using a copper oxide superconducting single crystal showing an embodiment of the present invention, and FIG. 6 is a diagram of a large power distribution type oscillator using a copper oxide superconducting single crystal showing an embodiment of the present invention. FIG. (Operating principle) Bi2212 is a high-temperature superconductor having a critical temperature of about 90 K, and has a crystal structure in which a superconducting layer 1 and a semiconductor layer 2 are laminated at an atomic level, as shown in FIG. Here, the thickness t of the superconducting layer 1 is 3 °, and the thickness d of the semiconductor layer 2 is 12 °. Therefore, when the voltage was measured by flowing the current I at right angles to each layer, as shown in FIG. 1 (b), many voltage branches appeared, and it was found that many tunnel junctions were stacked. See JP-A-2000-49395 and JP-A-2000-91654, which have already been proposed by the present inventors.

Therefore, the Bi2212 single crystal is processed by a focused ion beam processing method (for example, see Japanese Patent Application Laid-Open No. 2000-91654 already proposed by the present inventors) to form a stacked tunnel junction as shown in FIG. Successful fabrication. In FIG. 2, the mesa size of Bi2212 is 10 × 10 μm ² : J _C = 150 μA, the number of unit junctions is 4
0: Critical temperature T _C = 90K, height of the tunneling stack 5 is 200 nm.

The area of this element in the current direction is 1.5 × 1.
FIG. 3 shows the characteristics of the critical current I _C and the magnetic field B of the device when the intensity was set to 5 μm ² and a strong magnetic field was applied in parallel to the layer. In FIG. 3, the vertical axis represents the critical current I _c / maximum critical current I _cO (ratio) of the junction, and the horizontal axis represents the magnetic field (tesla). The maximum critical current I _cO of the junction is 0.3 μA.

In the vicinity of B ≒ 1 Tesla, the critical current I _C of the junction becomes extremely small. This means that one magnetic flux quantum enters each layer as shown in FIG. 4 and moves at a high speed in the layer with a small current I. At this time, when the current I is made to flow more than the minimum value of the critical current I _C of the junction, the magnetic flux quantum of each layer receives the Lorentz force by the current I and moves from left to right at the speed V _ff .

The voltage V generated at the junction at this time is expressed as follows: V = BV _ffh (1) Where h is the height of the junction, B = 1 Tesla,
From the experiment, V = 100 mV was obtained at h = 75 nm, indicating that the magnetic flux quantum moves at a speed of V _ff = 1.5 × 10 ⁶ m / s. The time Δt at which a row of magnetic flux quanta enters from the left and exits to the right is Δt = 10 ⁻¹² seconds from ΔtV _ff = L when the length is L. In this single pass, Δt
A voltage pulse of = ^10-12 seconds is generated between the electrodes. Since the magnetic flux quantum sequentially enters from the left and exits to the right, the repetition frequency f ₀ is f ₀ = 1 / Δt, so that a vibration at a frequency of 10 ¹² Hz, that is, 1 THz is excited in a junction having a size of 1.5 μm. You can see that it is done. Since the spatial wavelength λ of 1 THz is about 400 μm, an appropriate device is required to extract 1 THz vibration to the space.

FIG. 5A shows an example of the resonator.

Here, 10 is a resonator, 11 and 12 are conductors (strip lines), and 13 is a junction (IJJ's Vorte).
x).

[0015] Therefore, in the resonator 10, the magnetic field Bout ≒ 1 tesla addition to 1.5μm of the bond length (IJJ) 13, a DC current I _dc. The joint 13 has a length of λ / 4
And the strip lines 11 and 12. Junction 13
The alternating electric field E and the magnetic field H excited in FIG.
As shown in (c), the resonator is excited to generate 1TH in the line.
The electromagnetic wave energy of z is stored and can be taken out.

This energy is supplied from the DC power at the junction. The IV characteristics of the obtained junction are as shown in FIG. 5D, and V = Nf ₀ Φ ₀ ≒ 100 mV. Here, N is the number of layers and N = 50. The obtained power was about 1 μW from the power W = 50 μA × 100 mV = 10 ⁻⁶ W at the point (A) in FIG.

In FIG. 6, reference numeral 20 denotes a large output distributed oscillator, 21 and 22 denote conductors (strip lines), and 23 denotes a junction (Vortex of IJJ).

When four unit oscillators are arranged in parallel as shown in FIG. 6A, the power emitted from the right side becomes as shown in FIG.
As shown in FIG. A two-dimensional distribution structure is also possible, and higher power can be obtained.

It should be noted that the present invention is not limited to the above embodiment, but various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0020]

As described above in detail, according to the present invention, a THz band high-frequency oscillator is manufactured by electromagnetically coupling a micron-sized junction using a copper oxide superconducting single crystal and a resonator. be able to.

Therefore, an important high-speed electronic device of the next generation terabit information communication technology can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a crystal structure of Bi2212 and an IV characteristic of a junction thereof according to an example of the present invention.

FIG. 2 is a perspective view of a high-temperature superconducting Bi2212 manufactured by focused ion beam processing, showing an example of the present invention.

FIG. 3 is a characteristic diagram of a current I _C versus a magnetic field B at a junction of a copper oxide superconducting single crystal showing an example of the present invention.

FIG. 4 is a schematic view of a row of magnetic flux quanta during the joining of a copper oxide superconducting single crystal, showing an example of the present invention.

FIG. 5 is a diagram illustrating a high-frequency THz oscillator using a copper oxide superconducting single crystal according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a large power distributed oscillator using a copper oxide superconducting single crystal according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 superconducting layer 2 semiconductor layer 5 tunneling stack 10 resonator 11, 12, 21, 22 conductor (strip line) 13, 23 junction (Vortex of IJJ) 20 large power distributed oscillator

Claims (1)

[Claims] 1. A copper oxide superconducting single crystal junction having a layered structure is formed, a strong magnetic field is applied in parallel to the layers, magnetic flux quanta are generated in each layer, and the size of the junction in the layer direction and the magnetic flux are generated. The quantum is made to have the same size in the layer direction, and a current is flowed in the direction perpendicular to the junction layer at a critical current or more to generate a voltage.
A high-frequency electric field in the perpendicular direction is generated in a layer of not less than about 10 Hz and about 10 THz, an electromagnetic wave resonator electromagnetically coupled to the junction is provided, and an electromagnetic wave is excited in the electromagnetic wave resonator by the high-frequency electric field generated during the junction, thereby reducing energy. Stored as
A high-frequency oscillator using a copper oxide superconducting single crystal, which is taken out and used as needed.