From the History of Superconductivity

   Superconductors, materials that have no resistance to the flow of electricity, are one of the last great frontiers of scientific discovery. Not only have the limits of superconductivity not yet been reached, but the theories that explain superconductor behavior seem to be constantly under review. In 1911 superconductivity was first observed in mercury by Dutch physicist Heike Kamerlingh Onnes of Leiden University. When he cooled it to the temperature of liquid helium, 4 degrees Kelvin (–269°C), its resistance suddenly disappeared. The Kelvin scale represents an “absolute” scale of temperature. Thus, it was necessary for Onnes to come within 4 degrees of the coldest temperature that is theoretically attainable to witness the phenomenon of superconductivity. Later, in 1913, he won a Nobel Prize in physics for his research in this area.

   The next great milestone in understanding how matter behaves at extreme cold temperatures occurred in 1933. German researchers Walter Meissner and Robert Ochsenfeld discovered that a superconducting material will repel a magnetic field. A magnet moving by a conductor induces current in the conductor. This is the principle upon which the electric generator operates. But in a superconductor the induced currents exactly mirror the field that would have otherwise penetrated the superconducting material – causing the magnet to be repulsed. This phenomenon is known as strong diamagnetism and is today often referred to as the “Meissner effect”. The Meissner effect is so strong that a magnet can actually be levitated over a superconducting material.

    In subsequent decades other superconducting metals and compounds were discovered. But the first widely-accepted theoretical understanding of superconductivity was advanced in 1957 by American physicists John Bardeen, Leon Cooper, and John Schrieffer. Their Theory of Superconductivity became known as BCS theory, derived from the first letters of each man’s last name – and won them a Nobel Prize in 1972.

Another significant theoretical advancement came in 1962 when Brian D. Josephson, a graduate student at Cambridge University, predicted that electric current would flow between 2 superconducting materials – even when they are separated by a non-superconductor or insulator. His prediction was later confirmed and won him a share of the 1973 Nobel Prize in physics. This tunneling phenomenon is today known as the “Josephson effect” and has been applied to electric devices such as SQUID(superconducting quantum interference device), an instrument capable of detecting the weakest magnetic field.

  A truly breakthrough discovery was made in the field of superconductivity in1986. Alex Miller and Georg Bednorz, researchers at the IBM Research Laboratory in Ruschlicon (Switzerland), created a brittle ceramic compound that superconducted at the highest temperature then known: 30K. What made this discovery so remarkable was that ceramics are normally insulators. The Lanthanum, Barium, Copper and Oxygen compound that the scientists synthesized, behaved in a not-yet-understood way. The discovery of this first of the superconducting copper-oxides (cuprates) won the 2 men a Noble Prize the following year. It was later found that tiny amounts of this material were actually superconducting at 58 K, due to a small amount of lead having been added as a calibration standard – making the discovery even more noteworthy.

   Muller and Bednorz’s discovery triggered a flurry of activity in the field of superconductivity. Researchers around the world began “cooking” up ceramics of every imaginable combination in a quest for higher and higher Tc’s.

Note : SQUID – сверхпроводящий квантовый интерференционный датчик, СКВИД

 

2. In the text find equivalents to the following phrases:

- передний край научных открытий;

- постоянно пересматривать;

- теоретически достижимый;

- следующая значительная веха;

- отталкивать магнитное поле;

- значительное теоретическое продвижение;

- его предсказание было позднее подтверждено;

- хрупкое керамическое соединение;

- вести себя непонятным образом;

- из-за небольшого количества добавленного свинца;

- положить начало бурной деятельности

 

3. Form phrases by matching the words from 1-11 with the words a-k and translate:

1. induced 2. breakthrough 3, weakest   4. subsequent 5. superconducting  

6. widely-accepted 7. electric    8. ceramic  9. strong  10. tiny    11. theoretical

 

a) amount b) decades c) current d) materials  e) generator  

 f) understanding      g) diamagnetism     h) magnetic field i) compound   

 j) discovery k) advancement

  

 4. Write sentences using the words:

1. explain/ The theories / superconductor/ that / seem to be constantly/ behavior / under review.

2. decades /other superconducting metals/ In subsequent /and compounds/ were discovered.

3. moving by a conductor /A magnet /currents /induces / in the conductor.

4. strong diamagnetism/ This/ is known /phenomenon /as

5. in 1957/understanding /Widely-accepted /of/ was advanced /superconductivity

TALKING POINT

5. Discuss in pairs:

· materials known as superconductors

· the limits of superconductivity

· the first observation of superconductivity

· Kamerlingh Onnes’ discovery

· theoretical understanding of superconductivity

· the importance of Muller and Bednorz’s discovery

 

VOCABULARY STUDY      

 6. Complete the sentences with words from the box.

a) current  b) prevent c) basic d) visible e) theory   f) detector g) junction h) probability i) insulator  j) radiation

The heart of a superconducting tunnel … (1) consists of a thin layer of insulating material sandwiched between two superconductors. Such a sandwich of a superconductor, …(2) and superconductor is known as a superconducting tunnel junction.

Now, according to the law of classic physics, the insulator should …(3) an electric current from flowing through the junction. Quantum mechanics provides a loophole. According to this important …(4), an electron is represented as a probability wave: its position is therefore indeterminate. As a result there is a small …(5) that an electron in one superconductor can appear in the other superconductor, as if had tunneled through the insulator.

In the operation of a superconducting tunnel detector radio waves are directed onto a superconducting tunnel …(6) Electrons in the superconductors absorb the energy of the radiation. Higher-energy electrons have a far greater probability of tunneling through the insulator. The amount of electric …(7) passing through the insulator therefore increases with the amount ant type of radio waves striking the junction. By measuring the current one can infer the nature of the electromagnetic …(8) exciting the device. In spite of the rather exotic properties of the superconducting tunnel detector, its …(9) principle of operation – electrical conduction induced by incident radiation – is the same as that underlying the conventional detectors used in observatories for measuring …(10) radiation.

 

7. Write the following sentences in English:

В 1911 г. К. Оннес обнаружил, что при Т=4,2 К ртуть полностью теряет сопротивление электрическому току. Уменьшение сопротивления происходит очень резко в интервале нескольких сотых градуса. В дальнейшем потеря сопротивления наблюдалась и у других чистых веществ и у многих сплавов. Само явление получило название сверхпроводимости. Температуры перехода (transition) в сверхпроводящее состояние различны. Но всегда очень низки. Изучая фазовые переходы, великий советский физик-теоретик Л.Д. Ландау вместе с В.Л. Гинзбургом создал феноменологическую теорию сверхпроводимости. Эта теория дала возможность объяснить ряд существенных свойств сверхпроводников и впоследствии стала основой для создания теории сверхпроводников II рода и теории сверхпроводящих сплавов.

 

VOCABULARY STUDY

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