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High-Tc superconductor
Solid State Communications, Vol. 63, No. 4, p. 269, 1987. Printed in Great Britain.
0038-1098/87 $3.00 + .00 © 1987 Pergamon Journals Ltd.
HIGH- T~ SUPERCONDUCTOR Wu Hang-sheng and Weng Zheng-yu Department of Physics, University of Science and Technology of China, Hefei, Anhui, China (Received 6 March 1987 by IV. Y. Kuan)
In this Communication, we point out that it is possible to realize a high-T~ superconductor with the electron-phonon interaction. A model for it is proposed and the possibility whether the recently discovered superconducting material with T, = 100K is the superconductor of this kind is discussed. RECENTLY, A HIGH-T~ superconductor with its phonon spectrum g(to) and a reasonably larger parcritical temperature as high as 100K has been dis- ameter 2. Imagine a superconducting material with a highly covered by Zhao and Chen et al. A similar material "hardening" g(to) whose maximum frequency is to0. with Tc reaching to 98 K has been found by Chu and Wu. There is no doubt that this progress is very As an approximation, we represent the normalized effective phonon spectrum g(to) of this type by important. In this Communication, we point out that it is g(to) = 6(to -- too). (1) possible to realize a high-Tc superconductor with the electron-phonon interaction. A model for it is The T~ formula for this ideal Einstein spectrum is proposed and the possibility whether the recently dis- given (see paper [2], equation (8)) covered superconducting material is the superconducTc = 0.182to0(2- 0.65(_1 + 3/~')~ 1/2 tor of this kind is discussed. 1 + 2.5l,* ] , (2) In a recent paper [1], we devised a graphic method to analyze the numerical solution of the Eliashberg which holds only when 2 > 0.65(1 + 3#*). Taking equation, and obtain some conclusions about the rela- into account of the fact that the Debye temperature 0 tion between the superconducting Tc and the form of of the material Lil.zTit.804 is 650 K [3], we choose too the normalized effective phonon spectrum g(to). One to be equal to 600 K. Furthermore, choose 2 = 1.89 of the conclusions is that the superconducting T c could and/~* = 0.1. The value of To, calculated from equabe enhanced through the "hardening" ofg(to) (that is, tion (2), is equal to 100K. the weight ofg(to) shifting to the high frequency). So, Now it is clear that as the superconducting T~ is as a superconducting material is a high-T~ superconduc- high as 100 K, the values of 2, #* and too still remain tor if its normalized effective phonon spectrum g(to) is in the reasonable ranges. For the lack of experiments, a highly "hardening" one. Whereas the values of its we can say nothing about whether the recently disDebye temperature 0 and the dimensionless electron- covered high-T~ superconductor is the material with phonon interaction parameter 2 are only required to highly "hardening" g(to). However, we believe that a be reasonably large. The material to meet these re- superconducting material with the properties (a), (b) quirements, according to our opinion, should be that: and (c), listed in §2, is a realizable high-T~ supercon(a) It should be a multicomponent compound (or ductor. alloy). In a primitive cell. there are many atoms. And so, several branches of optical phonons exist. REFERENCES (b) These optical phonons should strongly inter1. Weng Zheng-yu & Wu Hang-sheng, Acta act with the conduction electrons. Physica Sinica (in Chinese). (c) The value of its Debye temperature 0 is rea2. Wu Hang-sheng & Ji Guangda, Scientia Sinica, sonably large. 22, 513 (1979). The first two properties ensure this material 3. B.K. Chakraverty & M.J. Sienko, Phys. Rev. 17, possessing a highly "hardening" normalized effective 3781 (1978).
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0038-1098/87 $3.00 + .00 © 1987 Pergamon Journals Ltd.
HIGH- T~ SUPERCONDUCTOR Wu Hang-sheng and Weng Zheng-yu Department of Physics, University of Science and Technology of China, Hefei, Anhui, China (Received 6 March 1987 by IV. Y. Kuan)
In this Communication, we point out that it is possible to realize a high-T~ superconductor with the electron-phonon interaction. A model for it is proposed and the possibility whether the recently discovered superconducting material with T, = 100K is the superconductor of this kind is discussed. RECENTLY, A HIGH-T~ superconductor with its phonon spectrum g(to) and a reasonably larger parcritical temperature as high as 100K has been dis- ameter 2. Imagine a superconducting material with a highly covered by Zhao and Chen et al. A similar material "hardening" g(to) whose maximum frequency is to0. with Tc reaching to 98 K has been found by Chu and Wu. There is no doubt that this progress is very As an approximation, we represent the normalized effective phonon spectrum g(to) of this type by important. In this Communication, we point out that it is g(to) = 6(to -- too). (1) possible to realize a high-Tc superconductor with the electron-phonon interaction. A model for it is The T~ formula for this ideal Einstein spectrum is proposed and the possibility whether the recently dis- given (see paper [2], equation (8)) covered superconducting material is the superconducTc = 0.182to0(2- 0.65(_1 + 3/~')~ 1/2 tor of this kind is discussed. 1 + 2.5l,* ] , (2) In a recent paper [1], we devised a graphic method to analyze the numerical solution of the Eliashberg which holds only when 2 > 0.65(1 + 3#*). Taking equation, and obtain some conclusions about the rela- into account of the fact that the Debye temperature 0 tion between the superconducting Tc and the form of of the material Lil.zTit.804 is 650 K [3], we choose too the normalized effective phonon spectrum g(to). One to be equal to 600 K. Furthermore, choose 2 = 1.89 of the conclusions is that the superconducting T c could and/~* = 0.1. The value of To, calculated from equabe enhanced through the "hardening" ofg(to) (that is, tion (2), is equal to 100K. the weight ofg(to) shifting to the high frequency). So, Now it is clear that as the superconducting T~ is as a superconducting material is a high-T~ superconduc- high as 100 K, the values of 2, #* and too still remain tor if its normalized effective phonon spectrum g(to) is in the reasonable ranges. For the lack of experiments, a highly "hardening" one. Whereas the values of its we can say nothing about whether the recently disDebye temperature 0 and the dimensionless electron- covered high-T~ superconductor is the material with phonon interaction parameter 2 are only required to highly "hardening" g(to). However, we believe that a be reasonably large. The material to meet these re- superconducting material with the properties (a), (b) quirements, according to our opinion, should be that: and (c), listed in §2, is a realizable high-T~ supercon(a) It should be a multicomponent compound (or ductor. alloy). In a primitive cell. there are many atoms. And so, several branches of optical phonons exist. REFERENCES (b) These optical phonons should strongly inter1. Weng Zheng-yu & Wu Hang-sheng, Acta act with the conduction electrons. Physica Sinica (in Chinese). (c) The value of its Debye temperature 0 is rea2. Wu Hang-sheng & Ji Guangda, Scientia Sinica, sonably large. 22, 513 (1979). The first two properties ensure this material 3. B.K. Chakraverty & M.J. Sienko, Phys. Rev. 17, possessing a highly "hardening" normalized effective 3781 (1978).
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