Experimental determinations of the Lorenz number

Experimental determination of the Lorenz number in Cu0.01Bi2Te2.7Lukas1, Liu2, Joshi3 et al. 2012Phys. Rev. B400200View full textAdd to dashboardCite

“…For the classical free electron model the Lorenz number is given as 2.44x10 -8 V 2 K -2 . 1 It is important to note that the Lorenz number, as described by the free electron model, is not an accurate value for most materials and in a given material depends on the detailed band structure, position of the Fermi level, and the temperature; for semiconductors this relates to the carrier concentration. Therefore, when lattice κ and carrier κ become comparable to each other, there must be a method for differentiating between the two components of total κ .…”

“…To date the separation of the two components has been accomplished through calculation by approximating the Lorenz number, and hence the carrier contribution, through various different formalisms. 1,[3][4] Determinations of the Lorenz number have also been made experimentally, 1 however there are few.…”

“…6,12 Neither method has been extensively used due to the fact that there are restrictions on the materials that can be measured because there must be a significant carrier contribution to the total thermal conductivity; also the experimental setup is rather difficult to realize. 1,[5][6][7][8][9] The advent of the Physical Properties Measurement System (PPMS) from Quantum Design makes the experimental setup and measurement readily possible for either method. The purpose of this paper is to present experimental techniques for the determination of the Lorenz number from which both the electronic and lattice contributions to the thermal conductivity can be directly extracted.…”

“…A classically large magnetic field is described as μB >> 1 where μ is the carrier mobility and B is the magnetic field. 1 When this limit is reached, the electronic component of κ is completely suppressed so that the measurement yields only the lattice portion of the thermal conductivity, from which carrier κ and hence the Lorenz number can be calculated using equations 1 and 2.…”

“…The total thermal conductivity is given by lattice carrier total κ κ κ + = (1) where carrier κ and lattice κ are the contributions to the thermal conductivity from the carriers and the lattice, respectively. Since only the total thermal conductivity can be measured, the contributions must be separated in some way.…”