%0 Book Section %1 statphys23_0011 %A Gu, Q. %B Abstract Book of the XXIII IUPAP International Conference on Statistical Physics %C Genova, Italy %D 2007 %E Pietronero, Luciano %E Loreto, Vittorio %E Zapperi, Stefano %K behavior bose-einstein condensation critical ferromagnetic statphys23 thermodynamics topic-2 transition %T Phase transitions in ferromagnetically coupled spinor Bose gases %U http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=11 %X Ferromagnetism is one of the best understood phenomena in nature. However, the ferromagnets being studied in the context of condensed matter physics are usually comprised of either classical particles (insulating ferromagnets) or fermions (itinerant ferromagnets). Bose systems are seldom touched. The realization of cold $^87$Rb gases has provided an opportunity to study Bose ferromagnets, and thus opens up a way to a comprehensive understanding of ferromagnetism in all kinds of condensed matters 1. .1cm The $^87$Rb gas is a typical ferromagnetically coupled spinor Bose system. There exists an intrinsic phase transition, Bose-Einstein condensation, in Bose gases. And the ferromagnetic coupling induces a ferromagnetic transition. Within mean-field theory, we suggested that the ferromagnetic transition occur always above Bose-Einstein condensation, regardless of the magnitude of the coupling 2. In addition, the ferromagnetic coupling increases critical temperatures of the both phase transitions. The phase diagram was also investigated by other groups later 3. Moreover, we calculated thermodynamic quantities of the system 4. The magnetic susceptibility obtained fits the Curie-Weiss law very well at all temperatures above the Curie point. The specific heat exhibits quite different critical behaviors near the two transition points. .1cm Whether there exists a Curie point in ferromagntic Bose gases is still controversial. Some argued that the ferromagnetic transition can not occur in cold atoms, as the total spin is conserved in an atomic quantum gas under experimental conditions 5. Further study is needed to clarify this problem.\\ 1) Q. Gu, Chapter 6 in Progress in Ferromagnetism Research, Ed. by V.N. Murray, (Nova Science Publishers, Inc., New York, 2006).\\ 2) Q. Gu, K. Bongs, and K. Sengstock, Phys. Rev. A 70, 063609 (2004); Q. Gu and R.A. Klemm, Phys. Rev. A 68, 031604(R) (2003).\\ 3) K. Kis-Szabo, P. Szepfalusy, and G. Szirmai, Phys. Rev. A 72, 023617 (2005); A. Ashhab, J. Low Temp. Phys. 140, 51 (2005).\\ 4) C. Tao, P. Wang, J. Qin, and Q. Gu, to be published.\\ 5) T. Isoshima, T. Ohmi, and K. Machida, J. Phys. Soc. Jpn. 69, 3864 (2000); W. Zhang, S. Yi, and L. You, Phys. Rev. A 70, 043611 (2004).

@incollection{statphys23_0011, abstract = {Ferromagnetism is one of the best understood phenomena in nature. However, the ferromagnets being studied in the context of condensed matter physics are usually comprised of either classical particles (insulating ferromagnets) or fermions (itinerant ferromagnets). Bose systems are seldom touched. The realization of cold $^{87}$Rb gases has provided an opportunity to study Bose ferromagnets, and thus opens up a way to a comprehensive understanding of ferromagnetism in all kinds of condensed matters [1]. \vskip .1cm The $^{87}$Rb gas is a typical ferromagnetically coupled spinor Bose system. There exists an intrinsic phase transition, Bose-Einstein condensation, in Bose gases. And the ferromagnetic coupling induces a ferromagnetic transition. Within mean-field theory, we suggested that the ferromagnetic transition occur always above Bose-Einstein condensation, regardless of the magnitude of the coupling [2]. In addition, the ferromagnetic coupling increases critical temperatures of the both phase transitions. The phase diagram was also investigated by other groups later [3]. Moreover, we calculated thermodynamic quantities of the system [4]. The magnetic susceptibility obtained fits the Curie-Weiss law very well at all temperatures above the Curie point. The specific heat exhibits quite different critical behaviors near the two transition points. \vskip .1cm Whether there exists a Curie point in ferromagntic Bose gases is still controversial. Some argued that the ferromagnetic transition can not occur in cold atoms, as the total spin is conserved in an atomic quantum gas under experimental conditions [5]. Further study is needed to clarify this problem.\\ 1) Q. Gu, Chapter 6 in {\em Progress in Ferromagnetism Research}, Ed. by V.N. Murray, (Nova Science Publishers, Inc., New York, 2006).\\ 2) Q. Gu, K. Bongs, and K. Sengstock, Phys. Rev. A {\bf 70}, 063609 (2004); Q. Gu and R.A. Klemm, Phys. Rev. A {\bf 68}, 031604(R) (2003).\\ 3) K. Kis-Szabo, P. Szepfalusy, and G. Szirmai, Phys. Rev. A {\bf 72}, 023617 (2005); A. Ashhab, J. Low Temp. Phys. {\bf 140}, 51 (2005).\\ 4) C. Tao, P. Wang, J. Qin, and Q. Gu, to be published.\\ 5) T. Isoshima, T. Ohmi, and K. Machida, J. Phys. Soc. Jpn. {\bf 69}, 3864 (2000); W. Zhang, S. Yi, and L. You, Phys. Rev. A {\bf 70}, 043611 (2004).}, added-at = {2007-06-20T10:16:09.000+0200}, address = {Genova, Italy}, author = {Gu, Q.}, biburl = {https://www.bibsonomy.org/bibtex/264502eb5be3bc936957b1b4d8d07d743/statphys23}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Pietronero, Luciano and Loreto, Vittorio and Zapperi, Stefano}, interhash = {dbc89796ae7efe43ffe2e7357ed17b5a}, intrahash = {64502eb5be3bc936957b1b4d8d07d743}, keywords = {behavior bose-einstein condensation critical ferromagnetic statphys23 thermodynamics topic-2 transition}, month = {9-13 July}, timestamp = {2007-06-20T10:16:09.000+0200}, title = {Phase transitions in ferromagnetically coupled spinor Bose gases}, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=11}, year = 2007 }