{"510001":{"#nid":"510001","#data":{"type":"event","title":"Magnetic field-induced quasiparticle instability and universal scaling behavior at finite fields in an S=1\/2 quantum antiferromagnet","body":[{"value":"\u003Cp\u003EQuasiparticles, such as phonons, magnons, rotons, and heavy electrons and holes, are ubiquitous in nature. Quasiparticles usually have a long lifetime due to the weak or absence of interactions between them. However, this picture breaks down in rare conditions. In this talk, I will describe the experimental realization of magnetic field-induced spontaneous (\u003Cem\u003ET\u003C\/em\u003E=0) magnon decays in an \u003Cem\u003ES\u003C\/em\u003E=1\/2 quantum antiferromagnet C\u003Csub\u003E9\u003C\/sub\u003EH\u003Csub\u003E18\u003C\/sub\u003EN\u003Csub\u003E2\u003C\/sub\u003ECuBr\u003Csub\u003E4 \u003C\/sub\u003Eusing the neutron scattering techniques [1]. The observed intriguing renormalization of one-magnon dispersion and magnon decays over a large region of the Brillouin Zone in the magnetic excitation specra can be well explained by the mechanism where the three-magnon interactions are present and the process of one-magnon decays into the two-magnon continuum is kinematically allowed [2]. Moreover, I will show that a universal scaling of the field-dependence of the Zeeman energy behaves in the same way as the temperature dependence of the spin gap in one-dimensional quantum magnets and agrees well with the calculation by the non-linear sigma model [3]. This result demonstrates the similarity between thermal and quantum fluctuations near the quantum critical point [4], where the intrinsic energy scales vanish.\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003Cstrong\u003EReference:\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E[1] T. Hong \u003Cem\u003Eet al\u003C\/em\u003E., submitted.\u003C\/p\u003E\u003Cp\u003E[2] M. E. Zhitomirsky and A. L. Chernyshev, Rev. Mod. Phys. \u003Cstrong\u003E85\u003C\/strong\u003E, 219 (2013).\u003C\/p\u003E\u003Cp\u003E[3] K. Damle and S. Sachdev, Phys. Rev. B \u003Cstrong\u003E57\u003C\/strong\u003E, 8307 (1998).\u003C\/p\u003E\u003Cp\u003E[4] S. Sachdev, Quantum Phase Transitions, Cambridge University Press (2001).\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":"","field_summary_sentence":[{"value":"Magnetic field-induced quasiparticle instability and universal scaling behavior at finite fields in an S=1\/2 quantum antiferromagnet"}],"uid":"27664","created_gmt":"2016-03-07 12:55:22","changed_gmt":"2017-04-13 21:16:23","author":"Alison Morain","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2016-04-07T16:00:00-04:00","event_time_end":"2016-04-07T17:00:00-04:00","event_time_end_last":"2016-04-07T17:00:00-04:00","gmt_time_start":"2016-04-07 20:00:00","gmt_time_end":"2016-04-07 21:00:00","gmt_time_end_last":"2016-04-07 21:00:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"126011","name":"School of Physics"}],"categories":[],"keywords":[{"id":"166937","name":"School of Physics"},{"id":"166896","name":"seminar"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1795","name":"Seminar\/Lecture\/Colloquium"}],"invited_audience":[{"id":"78751","name":"Undergraduate students"},{"id":"78761","name":"Faculty\/Staff"},{"id":"174045","name":"Graduate students"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Ca href=\u0022mailto:amorain@gatech.edu\u0022\u003Eamorain@gatech.edu\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":[],"slides":[],"orientation":[],"userdata":""}}}