Crossover temperature in the electron-phonon heat exchange in layered nanostructures
Семинары
Cеминар по теории конденсированных сред
Дата и время: вторник, 30 июля 2019 г., в 16:00
Место: Конференц-зал им. Блохинцева (4-й этаж), Лаборатория теоретической физики им. Н.Н. Боголюбова
Тема семинара: «Crossover temperature in the electron-phonon heat exchange in layered nanostructures»
Докладчик: Драгос-Виктор Ангел (Национальный институт физики и ядерной инженерии «Хория Хулубей», Румыния)
Аннотация:
We study theoretically the effect of the effective dimensionality of the phonon gas distribution on the heat exchange between electrons and phonons in layered nanostructures. If we denote the electrons temperature by Te and the phonons temperature by Tph, then the total heat power P is proportional– in general–to Txe − Txph, the exponent x being dependent on the effective dimensionality of the phonon gas distribution. If we vary the temperature in a wide enough range, the effective dimensionality of the phonon gas distribution changes going through a crossover around some temperature, TC. These changes are reflected by a change in x. On one hand, in a temperature range well below a crossover temperature TC only the lowest branches of the phonon modes are excited. They form a (quasi) two-dimensional gas, with x = 3.5. On the other hand, well above TC, the phonon gas distribution is quasi three-dimensional and one would expect to recover the three-dimensional results, with x = 5. But this is not the case in our layered structure. The exponent x has a complicated, non-monotonous dependence on temperature forming a “plateau region” just after the crossover temperature range, with x between 4.5 and 5. After the plateau region, x decreases, reaching values between 3.5 and 4 at the highest temperature used in our numerical calculations, which is almost two orders of magnitude higher than TC.