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Published January 2001 | public
Journal Article

Thermal conductance through discrete quantum channels


We have observed a quantized limiting value of the thermal conductance for each propagating phonon channel in a one-dimensional (1D), ballistic phonon waveguide: g_0=π^2k_B^2T/3h. To achieve this we have developed nanostructures with full three-dimensional relief that incorporate integral thermometers and heaters. These devices are comprised of an isolated thermal reservoir (phonon cavity) suspended above the sample substrate by four narrow insulating beams (phonon waveguides) with lateral dimensions ∼100 nm. We employ DC SQUID noise thermometry to measure the temperature of the phonon cavity non-perturbatively. Direct electrical contact from the suspended nanostructure to the room-temperature environment, crucial for these experiments, is attained by means of a very significant level of electrical filtering. These first experiments provide access to the mesoscopic regime for phonons, and open intriguing future possibilities for exploring thermal transport in very small systems. We are currently adapting and improving the ultrasensitive, extremely low dissipation DC SQUID techniques utilized in this work toward the ultimate goal of detecting individual thermal phonons.

Additional Information

© 2001 Elsevier Science B.V. Available online 13 December 2000. We thank M.C. Cross, R. Lifshitz, G. Kirczenow, and M. Blencowe, N. Wingreen, M. Lilly, and P. Burke for discussions, suggestions, and insights, and N. Bruckner for assisting in the growth of the low-stress silicon nitride at the University of California, Berkeley Microfabrication Laboratory. We thank M.B. Ketchen and members of the IBM Yorktown superconductivity group for advice, assistance, and the DC SQUID devices employed in our cryogenic electronics. One of us, J.A., would like to acknowledge the support of NSERC. Finally, we gratefully acknowledge the support from DARPA MTO/MEMS and NSF/DMR that enabled this work.

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