Flash Back!!
Let us go back to the beginning of 20th century when the foundation of superfluidity was laid. The story of superfluid begins in 1908 with liquid helium when a Dutch Physicist KamerlinghOnnes liquefied helium. Two years later he discovered that when helium was cooled below a temperature of 2.2K it would abruptly stop boiling. Further in 1923, Onnes and Dana measured its specific and latent heat and observed a strange discontinuity at 2.2 K which they failed to explain. Keesom and Wolfke were also working on liquid helium but it was until 1927 that they identified a transition between two phases at 2.1768K and named He I above it and He II below (the transition was known as the ‘lambda line’, because of the shape of the line). Work by Keesom and Clausius in 1932 also showed a strange anomaly in the heat capacity at 2.17K. All these findings were pointing towards a previously unknown physical effect at around 2.2K which was not known to scientists a quantum mechanical phenomenon but next came something truly baffling.
The decade 1930-1940 was quite remarkable for the development of superfluids.the ability of helium-II to flow through narrow slits (the existence of superleaks) was discovered in 1930 by willemkeesom.In 1935 in Cambridge, J.O. Wilhelm, A.D. Misenerand A.R. Clark had measured the viscosity of liquid helium with a torsion pendulum and found that it decreased sharply below lambda point.
At the same time pyotr Kapitsa was also working on the viscosity of the superfluid below lambda point.This period was the period of second world war and Stalin was working on nuclear weapons.so he forced kapitza to stay in Moscow and do the research work there only. Therefore it seems that the work at Moscow was independent of the work at cambridge
but Series of letters between Rutherford and kapitza in October 1937shows that the work in Moscow is not independent of work in Cambridge.After the death of Rutherford kapitza write a letter to neilsbohr on 10th December 1937 which was:
“My dear Kapitza,
. . . Bohr told me about his trip to you [in June 1937], and I am very
interested to hear of the work that you have been able to accomplish. No
doubt Pearson, when he returns, will be able to give us the latest informa-
tion about your big helium liquefier. The Mond laboratory is very flourishing,
and a large amount of work is in progress. . . Some interesting experiments
are also in progress on the extraordinary heat conductivity of helium at low
temperatures. The conductivity is very large for small differences of temperature, and falls rapidly with the quantity of heat transmitted."
The decade 1930-1940 was quite remarkable for the development of superfluids.the ability of helium-II to flow through narrow slits (the existence of superleaks) was discovered in 1930 by willemkeesom.In 1935 in Cambridge, J.O. Wilhelm, A.D. Misenerand A.R. Clark had measured the viscosity of liquid helium with a torsion pendulum and found that it decreased sharply below lambda point.
At the same time pyotr Kapitsa was also working on the viscosity of the superfluid below lambda point.This period was the period of second world war and Stalin was working on nuclear weapons.so he forced kapitza to stay in Moscow and do the research work there only. Therefore it seems that the work at Moscow was independent of the work at cambridge
but Series of letters between Rutherford and kapitza in October 1937shows that the work in Moscow is not independent of work in Cambridge.After the death of Rutherford kapitza write a letter to neilsbohr on 10th December 1937 which was:
“My dear Kapitza,
. . . Bohr told me about his trip to you [in June 1937], and I am very
interested to hear of the work that you have been able to accomplish. No
doubt Pearson, when he returns, will be able to give us the latest informa-
tion about your big helium liquefier. The Mond laboratory is very flourishing,
and a large amount of work is in progress. . . Some interesting experiments
are also in progress on the extraordinary heat conductivity of helium at low
temperatures. The conductivity is very large for small differences of temperature, and falls rapidly with the quantity of heat transmitted."
Since Bohr’s visit was in June 1937, this letter proves that kapitza was planning his experiments 6 months earlier.it also shows that kapitza did much more than a single experiment before sending his letter to NATURE magazine. Actually kapitza had an intuition that helium-II had something common with superconductors.that’s why kapitza proposed:
“by analogy with superconductors…..the helium below the lambda point enters a special state which might be called superfluid.”
This famous sentence introduced the word “superfluid” for the first time. His intuition was quite remarkable because superfluids and superconductors are indeed analoguos states of matter.
Now the question arises…how did that intuition came from? The idea is that at the same time fritz London and his brother Heinz put forward the idea that superconductors were quantum systems which had to be described by a macroscopic wave function and as we shall see now that London had not yet considered that it could be the case for liquid helium also.
At the same time allen and meisner were working on helium in Cambridge presented the results of series of measurements, from which they concluded:
“The observed type of flow….in which the velocity becomes almost independent of pressure, most certainly cannot be treated as laminaror even as ordinary turbulent flow. Consequently, any known formula cannot, from our data, give a value of viscositywhich would have much meaning.”
Allen discovered that ,when heat was applied to liquid helium –II on one side of a porous plug the pressure increased proportionally to the heat current so that the level of the first surface went up(it was later realised that the fountain pressure was in fact proportional to the temperature difference between two sides). For London it was no longer possible to doubt that this liquid had totally analomous properties for which a radically new interpretation was needed.
Landau Ley Davydovitch at that time considered to be most famous theoretical physist working on the superfluids. But the problem was that he was put into jail by Stalin. He had been accused of being one of the authors of leaflet criticizing the Soviet regime.
Kapitza had already written some letters to stalinin order to obtain the scientific equipment he needed for his research work. After landau’s arrest,kapitza started another fight to liberate him and eventually sent a letter to Molotov on april 6,1939,where, as published in English by P.E.Rubinin he wrote:
“In my recent studies on liquid helium close to the absolute zero, I have
succeeded in discovering a number of new phenomena. . . I am planning to
publish part of this work. . . but to do this I need theoretical help. In the Soviet
Union it is Landau who has the most perfect command of the theoretical field
I need, but unfortunately he has been in custody for a whole year. All this
time I have been hoping that he would be released because, frankly speaking,
I am unable to believe that he is a state criminal. . . It is true that he has
a very sharp tongue, the misuse of which together with his intelligence has
won him many enemies. . . but I have never noticed any sign of dishonest
behavior. . . the Soviet Union and worldwide has been deprived of Landau’s
brain for a whole year. Landau is in poor health and it will be a great shame
for the Soviet people if he is allowed to perish for nothing. . . ”
In this way kapitza helped landau to come back to work. On June 23,
1941, Kapitza52 and Landau62 sent two letters together for publication in
the Physical Review.
article by Landau start with nearly the same sentence: “It
is well known that liquid helium at temperatures below the λ-point possesses
a number of peculiar properties, the most important of which is superfluidity
discovered by P.L. Kapitza.”. For Landau, superfluidity had thus been
discovered by the man who had saved his life – P.L. Kapitza – and only by
him.
The article published was a great success. It introduced many new concepts and provided base for the future theories. It was closely resembled with the article of tisza but differ at some points.
The major difference between Landau’s theory and Tisza’s is in the nature
of the normal component: according to Landau it is made of “quasiparticles”,
a new concept he introduces to quantize the elementary excitations
of quantum fluids. In contrast, Tisza thinks in terms of ideal gases and
proposes that the normal component is made of the non-condensed atoms.
Shortly after the war, Peshkov did experiments to discriminate between
the predictions by Landau and by Tisza.69 Indeed, in the limit where T
tends to zero and according to Landau, the second sound velocity c2 should
tend to c/31/2 where c is the velocity of the ordinary sound, while Tisza
predicted that c2 should tend to zero. At the low temperature meeting which
Allen organized in Cambridge in 1946, a meeting which was called “LT0” by
Russell Donnelly 50 years later, Fritz London was asked to give the opening
talk.68 He explained that Peshkov’s preliminary results69 where not yet done
at low enough temperature to discriminate between Landau and Tisza, but
Peshkov’s experiments soon showed that Landau was right.
Soon many scientists started working on superfluids. But this progress stopped due to world war-2.
This period was the period of war, period of defence and most importantly period of existence. In the latter half of 20th century, both landau and London met with accident. Landau got the 1962 Nobel Prize when he recovered from coma. In 1978, kapitza also won the Nobel Prize for the work on superfluids. The theories of quantum mechanics reveal many new properties of superfluids. Superfluidity was discovered in helium-3 and many applications of it were discovered.
“by analogy with superconductors…..the helium below the lambda point enters a special state which might be called superfluid.”
This famous sentence introduced the word “superfluid” for the first time. His intuition was quite remarkable because superfluids and superconductors are indeed analoguos states of matter.
Now the question arises…how did that intuition came from? The idea is that at the same time fritz London and his brother Heinz put forward the idea that superconductors were quantum systems which had to be described by a macroscopic wave function and as we shall see now that London had not yet considered that it could be the case for liquid helium also.
At the same time allen and meisner were working on helium in Cambridge presented the results of series of measurements, from which they concluded:
“The observed type of flow….in which the velocity becomes almost independent of pressure, most certainly cannot be treated as laminaror even as ordinary turbulent flow. Consequently, any known formula cannot, from our data, give a value of viscositywhich would have much meaning.”
Allen discovered that ,when heat was applied to liquid helium –II on one side of a porous plug the pressure increased proportionally to the heat current so that the level of the first surface went up(it was later realised that the fountain pressure was in fact proportional to the temperature difference between two sides). For London it was no longer possible to doubt that this liquid had totally analomous properties for which a radically new interpretation was needed.
Landau Ley Davydovitch at that time considered to be most famous theoretical physist working on the superfluids. But the problem was that he was put into jail by Stalin. He had been accused of being one of the authors of leaflet criticizing the Soviet regime.
Kapitza had already written some letters to stalinin order to obtain the scientific equipment he needed for his research work. After landau’s arrest,kapitza started another fight to liberate him and eventually sent a letter to Molotov on april 6,1939,where, as published in English by P.E.Rubinin he wrote:
“In my recent studies on liquid helium close to the absolute zero, I have
succeeded in discovering a number of new phenomena. . . I am planning to
publish part of this work. . . but to do this I need theoretical help. In the Soviet
Union it is Landau who has the most perfect command of the theoretical field
I need, but unfortunately he has been in custody for a whole year. All this
time I have been hoping that he would be released because, frankly speaking,
I am unable to believe that he is a state criminal. . . It is true that he has
a very sharp tongue, the misuse of which together with his intelligence has
won him many enemies. . . but I have never noticed any sign of dishonest
behavior. . . the Soviet Union and worldwide has been deprived of Landau’s
brain for a whole year. Landau is in poor health and it will be a great shame
for the Soviet people if he is allowed to perish for nothing. . . ”
In this way kapitza helped landau to come back to work. On June 23,
1941, Kapitza52 and Landau62 sent two letters together for publication in
the Physical Review.
article by Landau start with nearly the same sentence: “It
is well known that liquid helium at temperatures below the λ-point possesses
a number of peculiar properties, the most important of which is superfluidity
discovered by P.L. Kapitza.”. For Landau, superfluidity had thus been
discovered by the man who had saved his life – P.L. Kapitza – and only by
him.
The article published was a great success. It introduced many new concepts and provided base for the future theories. It was closely resembled with the article of tisza but differ at some points.
The major difference between Landau’s theory and Tisza’s is in the nature
of the normal component: according to Landau it is made of “quasiparticles”,
a new concept he introduces to quantize the elementary excitations
of quantum fluids. In contrast, Tisza thinks in terms of ideal gases and
proposes that the normal component is made of the non-condensed atoms.
Shortly after the war, Peshkov did experiments to discriminate between
the predictions by Landau and by Tisza.69 Indeed, in the limit where T
tends to zero and according to Landau, the second sound velocity c2 should
tend to c/31/2 where c is the velocity of the ordinary sound, while Tisza
predicted that c2 should tend to zero. At the low temperature meeting which
Allen organized in Cambridge in 1946, a meeting which was called “LT0” by
Russell Donnelly 50 years later, Fritz London was asked to give the opening
talk.68 He explained that Peshkov’s preliminary results69 where not yet done
at low enough temperature to discriminate between Landau and Tisza, but
Peshkov’s experiments soon showed that Landau was right.
Soon many scientists started working on superfluids. But this progress stopped due to world war-2.
This period was the period of war, period of defence and most importantly period of existence. In the latter half of 20th century, both landau and London met with accident. Landau got the 1962 Nobel Prize when he recovered from coma. In 1978, kapitza also won the Nobel Prize for the work on superfluids. The theories of quantum mechanics reveal many new properties of superfluids. Superfluidity was discovered in helium-3 and many applications of it were discovered.