|Title :||The seminar by Theory Div.: Microwave absorption by the anti-ferromagnetic spin-1/2 Heisenberg-Ising chain|
PM 4:00-PM 5:00
|Place :||Seminar Room 5 (A615), 6th Floor, ISSP|
|Lecturer :||Mr. Michael Brockmann|
|Affiliation :||Bergische Universitat Wuppertal|
|Summary :||We analyze the absorption of microwaves by the one-dimensional spin-1/2 Heisenberg-Ising magnet exposed to a static magnetic field. This model is most relevant for the description of the low-energy behavior of quasi one-dimensional anti-ferromagnetic materials, such as LiCuVO$_4$, which is dominated by many-body effects.Due to the anisotropic exchange between electrons the sharp absorption resonance, which would be expected for paramagnetic materials, is shifted and broadened. In experiments of electron spin resonance (ESR) this effect is usually quantified by measuring the maximum of the absorption profile and the distance between the inflection points.
We argue that, from a theoretical point of view, it is more appropriate to define the resonance shift and the line width by means of the first few moments of the absorbed intensity. These are determined by short-range correlation functions. Due to the integrability of the model short-range correlation functions can be calculated exactly over the whole range of temperatures and for arbitrary magnetic fields.
Thus, we obtain exact results for the resonance shift and the line width of the absorbed intensity of the spin-1/2 Heisenberg-Ising chain.
Additionally, we performed numerical calculations of the full absorption profile which are supported by the exact data as well as exact two-spinon calculations in the massive regime.
|Committee Chair :||OSHIKAWA Masaki (ext.63275)
e-mail: oshikawa :at: issp.u-tokyo.ac.jp