000097667 001__ 97667 000097667 005__ 20210118122853.0 000097667 037__ $$aTAZ-TFM-2020-206 000097667 041__ $$aeng 000097667 1001_ $$aRomán Roche, Juan 000097667 24200 $$aPhoton condensation in magnetic cavity QED 000097667 24500 $$aCondensación fotónica en magnetic cavity QED 000097667 260__ $$aZaragoza$$bUniversidad de Zaragoza$$c2020 000097667 506__ $$aby-nc-sa$$bCreative Commons$$c3.0$$uhttp://creativecommons.org/licenses/by-nc-sa/3.0/ 000097667 520__ $$aMore than 47 years ago Hepp and Lieb showed that photon condensation was theoretically possible in Dicke’s model. In this model, symmetry breaking was induced by the coupling of an electromagnetic cavity to the electric dipoles of N free atoms in the thermodynamic limit. The experimental realization of this model has been pursued for the last 47 years. However, the transition has never been measured. During this time, the community has enjoyed a tortuous succession of proposals on how to achieve photon condensation, each shortly matched with a corresponding no-go theorem.<br />In this Master’s Thesis we present a no-go theorem that unifies all these no-go theorems (including some recent ones) and we propose a rather straightforward way to avoid them: harnessing magnetic coupling. Therefore, we solve this long-standing theoretical controversy and provide a realistic experimental layout to measure the transition, using magnetic molecules (instead of electric-dipole-coupled ones).<br />This Master’s Thesis is divided in two blocks. The first block discusses the problem of photon condensation as presented in the literature, with electric-dipole coupling. Section 1 starts with a brief presentation of Pauli’s equation and how it leads to the Hamiltonian of the model under study, we then proceed to give a thorough overview of the historical contributions to the topic, from Hepp and Lieb’s original contribution to the present day. Then, in Sec. 2, we present a unified no-go theorem that settles the debate, proving that photon condensation does not occur when the coupling between light and matter is through the electric dipole. The second block explores magnetic cavity QED. In Sec. 3 we introduce Zeeman coupling in our Hamiltonian of the model while considering molecules without electric dipole, we show that this leads to the Dicke model, in which superradiance occurs. After finding that magnetic cavity QED permits photon condensation we test the robustness of the model against some generalizations. Following the success in Sec. 3, in Sec. 4 we discuss a transmission experiment designed to measure the phase transition. Finally, we draw some conclusions from our results and outline possible continuations. Technical details are left for the appendices.<br /><br /> 000097667 521__ $$aMáster Universitario en Física y Tecnologías Físicas 000097667 540__ $$aDerechos regulados por licencia Creative Commons 000097667 700__ $$aZueco Láinez, David$$edir. 000097667 7102_ $$aUniversidad de Zaragoza$$bFísica de la Materia Condensada$$cFísica de la Materia Condensada 000097667 8560_ $$f717281@unizar.es 000097667 8564_ $$s2694125$$uhttps://zaguan.unizar.es/record/97667/files/TAZ-TFM-2020-206.pdf$$yMemoria (eng) 000097667 8564_ $$s523265$$uhttps://zaguan.unizar.es/record/97667/files/TAZ-TFM-2020-206_ANE.pdf$$yAnexos (eng) 000097667 909CO $$ooai:zaguan.unizar.es:97667$$pdriver$$ptrabajos-fin-master 000097667 950__ $$a 000097667 951__ $$adeposita:2021-01-18 000097667 980__ $$aTAZ$$bTFM$$cCIEN 000097667 999__ $$a20200625112827.CREATION_DATE