Zero entropy
Super fluids not only possess zero viscosity but they also approach zero entropy. This means that a pure super fluid theoretically possesses the lowest possible energy that a quantum mechanical physical system can have. It is the energy of its ground state. It still possesses some energy, called zero-point energy, because all quantum systems undergo fluctuations in their ground state. A pure super fluid has zero entropy because its energy is below the minimum potential energy required to be able to convert to any other kind of energy such as heat (zero-point energy is the same as the vacuum energy which is not available as thermal energy )
A direct implication of this property can be seen in the following experiment."If you set [down] a cup with a liquid circulating around and you come back 10 minutes later, of course it's stopped moving," says John Beamish, an experimental physicist at the University of Alberta in Edmonton. Atoms in the liquid will collide with one another and slow down. "But if you did that with helium at low temperature and came back a million years later," he says, "it would still be moving."
This Since all the atoms in superfluid are in same quantum state, therefore the total entropy of the system is zero.
S=k ln Ω
Where S is the total entropy of the system
k is the Boltzmann constant
& Ω is the total number of microstates
Now, since all the atoms are in same quantum state, therefore the total number of ways in which they can be arranged in a system is exactly one. The number of microstates basically depends on two major factors:
1. Quantum states of particles
2. Whether particles are alike or different
Superfluids are the bosonic particles and all the bosons are identical. Therefore total number of microstates is 1.
Therefore, Ω=1
By the above relation S=0.
But we know that exact zero entropy is only achieved at 0 K. This justifies the fact that there has to be two types of fluid present in the superfluids. Superfluids consist of two types of fluids: one normal component and another superfluid component. As the temperature becomes lower and lower the superfluid component increases further. This leads to the strange phenomenon of a two-fluid model, in which there can be a transfer of mass without a transfer of energy: when such a fluid/superfluid system is introduced in a setup that would normally trap a fluid, the superfluid can flow out due to its zero-viscosity property, leaving the normal fluid behind. Thus, part of the fluid system's mass is transferred without any energy transfer (since the superfluid has zero entropy).
Super fluids exhibit both quantum mechanical behaviors and classic mechanical behaviors at the same time. For example, super fluids can transmit ordinary sound (pressure) waves, a classical phenomenon. The reason for this duality is that super fluids contain of a small percentage of atoms in ordinary (random and variable) quantum states along with atoms that are all confined to one quantum state. The percentage of ordinary randomly quantized atoms approaches zero as absolute zero is approached (absolute zero has never been experimentally observed and you will learn why shortly). This is called the two-fluid model of super fluids. All super fluids, in practice, have at least some proportion of atoms in an ordinary fluid state.
The properties of super fluids have fascinated physicists from the time of Landau and Feynman - and continue to do so. Now an international team of physicists from Helsinki, Leiden, Moscow and Grenoble have observed a double-quantum vortex in super fluid helium-3 for the first time
A direct implication of this property can be seen in the following experiment."If you set [down] a cup with a liquid circulating around and you come back 10 minutes later, of course it's stopped moving," says John Beamish, an experimental physicist at the University of Alberta in Edmonton. Atoms in the liquid will collide with one another and slow down. "But if you did that with helium at low temperature and came back a million years later," he says, "it would still be moving."
This Since all the atoms in superfluid are in same quantum state, therefore the total entropy of the system is zero.
S=k ln Ω
Where S is the total entropy of the system
k is the Boltzmann constant
& Ω is the total number of microstates
Now, since all the atoms are in same quantum state, therefore the total number of ways in which they can be arranged in a system is exactly one. The number of microstates basically depends on two major factors:
1. Quantum states of particles
2. Whether particles are alike or different
Superfluids are the bosonic particles and all the bosons are identical. Therefore total number of microstates is 1.
Therefore, Ω=1
By the above relation S=0.
But we know that exact zero entropy is only achieved at 0 K. This justifies the fact that there has to be two types of fluid present in the superfluids. Superfluids consist of two types of fluids: one normal component and another superfluid component. As the temperature becomes lower and lower the superfluid component increases further. This leads to the strange phenomenon of a two-fluid model, in which there can be a transfer of mass without a transfer of energy: when such a fluid/superfluid system is introduced in a setup that would normally trap a fluid, the superfluid can flow out due to its zero-viscosity property, leaving the normal fluid behind. Thus, part of the fluid system's mass is transferred without any energy transfer (since the superfluid has zero entropy).
Super fluids exhibit both quantum mechanical behaviors and classic mechanical behaviors at the same time. For example, super fluids can transmit ordinary sound (pressure) waves, a classical phenomenon. The reason for this duality is that super fluids contain of a small percentage of atoms in ordinary (random and variable) quantum states along with atoms that are all confined to one quantum state. The percentage of ordinary randomly quantized atoms approaches zero as absolute zero is approached (absolute zero has never been experimentally observed and you will learn why shortly). This is called the two-fluid model of super fluids. All super fluids, in practice, have at least some proportion of atoms in an ordinary fluid state.
The properties of super fluids have fascinated physicists from the time of Landau and Feynman - and continue to do so. Now an international team of physicists from Helsinki, Leiden, Moscow and Grenoble have observed a double-quantum vortex in super fluid helium-3 for the first time