Second sound

Second sound is a quantum mechanical phenomenon in which heat transfer occurs by wave-like motion, rather than by the more usual mechanism of diffusion. Heat takes the place of pressure in normal sound waves. This leads to a very high thermal conductivity. It is known as "second sound" because the wave motion of heat is similar to the propagation of sound in air.

Second sound is observed in liquid helium (³He as well as ⁴He) and in ⁶Li at temperatures below the lambda point. In this state, known as helium II, ⁴He has the highest thermal conductivity of any known material (several hundred times higher than copper).

Second sound in helium II

At temperatures below the lambda point 2.1768 K, ⁴He enters a superfluid state and has almost perfect heat conduction. The helium is in a macroscopic quantum state. At temperatures falling toward 0 K the speed of temperature and entropy waves increases. These can be generated and observed in a resonator. At a temperature of 1.8 K the temperature wave propagates at approximately 20 m/s.

Second sound in other media

³He has second sound below 2.5 mK, ⁶Li also close to 0 K. Superfluidity of ⁶Li has been observed at a temperature of 50 nK at MIT in April 2005.. Second sound has also been observed in some dielectric solids, such as Bi and NaF.

References

V. Narayanamurti and R.C. Dynes. Phys. Rev. Lett. 28, 1461, (1972). T.F. McNelly, S.J. Rogers, D.J. Chanin, R.J. Rollefson, W.M. Goubau, G.E. Schmidt, I. A. Krumhansl, R.O. Pohl, Phys. Rev. Lett. 24, 100 (1970). H.E. Jackson, C.T. Walker. Phys. Rev. B, V. 3 (4), p. 1428 (1971).

Bibliography

• C.T. Lane, H.A. Fairbank, and W.M. Fairbank, "Second Sound in Liquid Helium II," Phys. Rev. 71, 600 (1947). Retrieved on April 15, 2007.
• Sinyan Shen, Surface Second Sound in Superfluid Helium. PhD Dissertation (1973). http://adsabs.harvard.edu/abs/1973PhDT.......142S
• V. Peshkov, "'Second Sound' in Helium II," J. Phys. (Moscow) 8, 381 (1944)
• U. Piram, "Numerical investigation of second sound in liquid helium," Dipl.-Ing. Dissertation (1991). Retrieved on April 15, 2007.
• H.E. Jackson, C.T. Walker, and T.F. McNelly, "Second sound in NaF," Phys. Rev. Letters 25, 26 - 28 (1970)
• V. Narayanamurti, and R.C. Dynes, "Observation of second sound in Bismuth," Phys. Rev. Letters 28, 1461 - 1465 (1972)

See also

• Third sound