1,398 research outputs found
High-frequency oscillations in low-dimensional conductors and semiconductor superlattices induced by current in stack direction
A narrow energy band of the electronic spectrum in some direction in
low-dimensional crystals may lead to a negative differential conductance and
N-shaped I-V curve that results in an instability of the uniform stationary
state. A well-known stable solution for such a system is a state with electric
field domain. We have found a uniform stable solution in the region of negative
differential conductance. This solution describes uniform high-frequency
voltage oscillations. Frequency of the oscillation is determined by antenna
properties of the system. The results are applicable also to semiconductor
superlattices.Comment: 8 pages, 3 figure
Electron Bloch Oscillations and Electromagnetic Transparency of Semiconductor Superlattices in Multi-Frequency Electric Fields
We examine phenomenon of electromagnetic transparency in semiconductor
superlattices (having various miniband dispersion laws) in the presence of
multi-frequency periodic and non-periodic electric fields. Effects of induced
transparency and spontaneous generation of static fields are discussed. We paid
a special attention on a self-induced electromagnetic transparency and its
correlation to dynamic electron localization. Processes and mechanisms of the
transparency formation, collapse, and stabilization in the presence of external
fields are studied. In particular, we present the numerical results of the time
evolution of the superlattice current in an external biharmonic field showing
main channels of transparency collapse and its partial stabilization in the
case of low electron density superlattices
Π£ΡΠ΅Π±Π½ΡΠΉ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡ Π΄Π»Ρ ΠΈΠ·ΡΡΠ΅Π½ΠΈΡ ΡΡΡΡΠΊΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ° ΠΊΠ°ΠΊ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΠΎΠ³ΠΎ (Π ΠΠ) "Π Π΄ΠΎΠ±ΡΡΠΉ ΠΏΡΡΡ!" ΠΈ ΠΊΠΎΠΌΠΏΡΡΡΠ΅ΡΠ½ΡΠΉ ΡΡΠ΅Π½Π°ΠΆΠ΅Ρ ΠΏΠΎ Π ΠΠ
A description of the nationally oriented training complex for learning Russian as a foreign language "V Dobryi Putβ!" for German speakers which includes a textbook, an audio-supplement, a video-film and a test system is given. The computer-based training system, designed for this complex ensures effective teaching foreign students Russian phonetics, vocabulary, grammar, speech etiquette, and also facilitates the formation of the necessary communication skills.ΠΡΠΈΠ²ΠΎΠ΄ΠΈΡΡΡ ΠΎΠΏΠΈΡΠ°Π½ΠΈΠ΅ Π½Π°ΡΠΈΠΎΠ½Π°Π»ΡΠ½ΠΎ-ΠΎΡΠΈΠ΅Π½ΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ ΡΡΠ΅Π±Π½ΠΎΠ³ΠΎ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ° ΠΏΠΎ Π ΠΠ Π΄Π»Ρ Π½Π΅ΠΌΠ΅ΡΠΊΠΎΠ³ΠΎΠ²ΠΎΡΡΡΠΈΡ
"Π Π΄ΠΎΠ±ΡΡΠΉ ΠΏΡΡΡ!", ΠΊΠΎΡΠΎΡΡΠΉ Π²ΠΊΠ»ΡΡΠ°Π΅Ρ ΡΡΠ΅Π±Π½ΠΈΠΊ, Π°ΡΠ΄ΠΈΠΎΠΏΡΠΈΠ»ΠΎΠΆΠ΅Π½ΠΈΠ΅, Π²ΠΈΠ΄Π΅ΠΎΡΠΈΠ»ΡΠΌ ΠΈ ΡΠΈΡΡΠ΅ΠΌΡ ΡΠ΅ΡΡΠΎΠ². Π Π°Π·ΡΠ°Π±ΠΎΡΠ°Π½Π½ΡΠΉ Π΄Π»Ρ Π΄Π°Π½Π½ΠΎΠ³ΠΎ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ° ΠΊΠΎΠΌΠΏΡΡΡΠ΅ΡΠ½ΡΠΉ ΡΡΠ΅Π½Π°ΠΆΠ΅Ρ ΠΎΠ±Π΅ΡΠΏΠ΅ΡΠΈΠ²Π°Π΅Ρ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΠ΅ ΠΎΠ±ΡΡΠ΅Π½ΠΈΠ΅ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΡΡ
ΡΡΠ°ΡΠΈΡ
ΡΡ ΡΡΡΡΠΊΠΎΠΉ ΡΠΎΠ½Π΅ΡΠΈΠΊΠ΅, Π»Π΅ΠΊΡΠΈΠΊΠ΅, Π³ΡΠ°ΠΌΠΌΠ°ΡΠΈΠΊΠ΅, ΡΠ΅ΡΠ΅Π²ΠΎΠΌΡ ΡΡΠΈΠΊΠ΅ΡΡ, Π° ΡΠ°ΠΊΠΆΠ΅ ΠΎΠ±Π»Π΅Π³ΡΠ°Π΅Ρ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ Π½Π΅ΠΎΠ±Ρ
ΠΎΠ΄ΠΈΠΌΡΡ
ΠΊΠΎΠΌΠΌΡΠ½ΠΈΠΊΠ°ΡΠΈΠ²Π½ΡΡ
Π½Π°Π²ΡΠΊΠΎΠ²
Fractional and unquantized dc voltage generation in THz-driven semiconductor superlattices
We consider the spontaneous creation of a dc voltage across a strongly
coupled semiconductor superlattice subjected to THz radiation. We show that the
dc voltage may be approximately proportional either to an integer or to a half-
integer multiple of the frequency of the applied ac field, depending on the
ratio of the characteristic scattering rates of conducting electrons. For the
case of an ac field frequency less than the characteristic scattering rates, we
demonstrate the generation of an unquantized dc voltage.Comment: 6 pages, 3 figures, RevTEX, EPSF. Revised version v3: corrected typo
ΠΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½Π°Ρ ΠΊΠΎΠΌΠΌΡΠ½ΠΈΠΊΠ°ΡΠΈΡ ΠΈ ΠΏΡΠ΅ΠΏΠΎΠ΄Π°Π²Π°Π½ΠΈΠ΅ ΡΡΡΡΠΊΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ° ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΡΠΌ ΡΡΡΠ΄Π΅Π½ΡΠ°ΠΌ Π½Π° Π»Π΅ΡΠ½ΠΈΡ ΡΠ·ΡΠΊΠΎΠ²ΡΡ ΠΊΡΡΡΠ°Ρ
Introduction: the article considers the content and methods of teaching Russian as a foreign language at language summer courses with due account to (as a form of study-abroad training) the motives of intercultural communication. The specifics of teaching Russian to international students in the cultural field of Ukraine is revealed. The timeliness of the study is determined by constantly increasing academic mobility of students and the need for the development of modern educational technologies. The main purpose of the article is to present an integrated approach to Russian as a foreign language teaching at language summer courses, when cultural needs of the trainees and the motives of intercultural communication are considered. Materials and Methods: teaching methodology draws on specific methods of teaching Russian as a foreign language and models of intercultural competence development. Educational materials for practical teaching of the Russian language are presented; qualitative and quantitative methods to research intercultural communication motives (written questionnaires and interviews on key topics) are used. Results: through working with the learners of language courses β students of Austrian universities β the data on the learnersβ motivation factors, the most relevant topics for intercultural dialogue, some important aspects of Russian grammar, and also the data on the most popular knowledge about Ukraine are obtained and carefully analysed. The analysis of the obtained data, carried out by the authors of the study, allowed to optimise the content of the educational process and to incre ase its effectiveness. Discussion and Conclusions: teaching Russian to foreigners, showing a keen interest in the cultural values of Ukraine, suggests a parallel formation of intercultural competence based on understanding the local cultural realities. The presented approach to RFL teaching within the framework of the language summer courses provides not only a strong uptake of linguistic material by international students and considerable improvements in their level of proficiency in the Russian language, but also a significant enhancement of the intercultural competence of the trainees on the basis of a variety of teaching techniques and active intercultural communication of international students with native Russian language speakers when working in tandem. The practical significance of the study is determined by the fact that the proposed approach to Russian as a foreign language teaching may find wide applicatio n in the training of foreigners at language summer courses; research perspectives are determined by the continuous development of this form of education and the increased importance of intercultural compete nce in the practice of cultural interaction.ΠΠ²Π΅Π΄Π΅Π½ΠΈΠ΅: Π² ΡΡΠ°ΡΡΠ΅ ΡΠ°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°ΡΡΡΡ ΡΠΎΠ΄Π΅ΡΠΆΠ°Π½ΠΈΠ΅ ΠΈ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠ° ΠΎΠ±ΡΡΠ΅Π½ΠΈΡ ΡΡΡΡΠΊΠΎΠΌΡ ΡΠ·ΡΠΊΡ ΠΊΠ°ΠΊ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΠΎΠΌΡ Π½Π° Π»Π΅ΡΠ½ΠΈΡ
ΡΠ·ΡΠΊΠΎΠ²ΡΡ
ΠΊΡΡΡΠ°Ρ
, ΠΎΡΡΠ°ΠΆΠ°ΡΡΠΈΡ
ΠΌΠΎΡΠΈΠ²Ρ ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΉ ΠΊΠΎΠΌΠΌΡΠ½ΠΈΠΊΠ°ΡΠΈΠΈ. Π Π°ΡΠΊΡΡΡΠ° ΡΠΏΠ΅ΡΠΈΡΠΈΠΊΠ° ΠΏΡΠ΅ΠΏΠΎΠ΄Π°Π²Π°Π½ΠΈΡ ΡΡΡΡΠΊΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ° ΡΡΡΠ΄Π΅Π½ΡΠ°ΠΌ-ΠΈΠ½ΠΎΡΡΡΠ°Π½ΡΠ°ΠΌ Π² ΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΌ ΠΏΠΎΠ»Π΅ Π£ΠΊΡΠ°ΠΈΠ½Ρ. ΠΠΊΡΡΠ°Π»ΡΠ½ΠΎΡΡΡ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΠ΅ΡΡΡ Π²ΠΎΠ·ΡΠ°ΡΡΠ°ΡΡΠ΅ΠΉ Π°ΠΊΠ°Π΄Π΅ΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΌΠΎΠ±ΠΈΠ»ΡΠ½ΠΎΡΡΡΡ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² ΠΈ Π½Π΅ΠΎΠ±Ρ
ΠΎΠ΄ΠΈΠΌΠΎΡΡΡΡ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠΊΠΈ ΡΠΎΠ²ΡΠ΅ΠΌΠ΅Π½Π½ΡΡ
ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°ΡΠ΅Π»ΡΠ½ΡΡ
ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠΉ Π΄Π»Ρ ΠΈΡ
ΠΎΠ±ΡΡΠ΅Π½ΠΈΡ. Π¦Π΅Π»Ρ ΡΡΠ°ΡΡΠΈ β ΠΏΡΠ΅Π΄ΡΡΠ°Π²ΠΈΡΡ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ½ΡΠΉ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄ Π² ΠΏΡΠ΅ΠΏΠΎΠ΄Π°Π²Π°Π½ΠΈΠΈ ΡΡΡΡΠΊΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ° ΠΊΠ°ΠΊ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΠΎΠ³ΠΎ Π½Π° Π»Π΅ΡΠ½ΠΈΡ
ΡΠ·ΡΠΊΠΎΠ²ΡΡ
ΠΊΡΡΡΠ°Ρ
, ΠΏΡΠΈ ΠΊΠΎΡΠΎΡΠΎΠΌ ΡΡΠΈΡΡΠ²Π°ΡΡΡΡ ΠΊΡΠ»ΡΡΡΡΠ½ΡΠ΅ Π·Π°ΠΏΡΠΎΡΡ ΠΎΠ±ΡΡΠ°Π΅ΠΌΡΡ
ΠΈ ΠΌΠΎΡΠΈΠ²Ρ ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΉ ΠΊΠΎΠΌΠΌΡΠ½ΠΈΠΊΠ°ΡΠΈΠΈ. ΠΠ°ΡΠ΅ΡΠΈΠ°Π»Ρ ΠΈ ΠΌΠ΅ΡΠΎΠ΄Ρ: ΠΌΠ΅ΡΠΎΠ΄ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠΌ ΠΎΠ±ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ Π½Π°ΡΡΠΎΡΡΠ΅Π³ΠΎ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΡΠ²Π»ΡΡΡΡΡ ΡΠ°ΡΡΠ½Π°Ρ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠ° ΠΏΡΠ΅ΠΏΠΎΠ΄Π°Π²Π°Π½ΠΈΡ ΡΡΡΡΠΊΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ° ΠΊΠ°ΠΊ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΠΎΠ³ΠΎ ΠΈ ΠΌΠΎΠ΄Π΅Π»ΠΈ ΡΠ°Π·Π²ΠΈΡΠΈΡ ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΉ ΠΊΠΎΠΌΠΏΠ΅ΡΠ΅Π½ΡΠΈΠΈ. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ ΡΡΠ΅Π±Π½ΡΠ΅ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Ρ Π΄Π»Ρ ΠΏΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΏΡΠ΅ΠΏΠΎΠ΄Π°Π²Π°Π½ΠΈΡ ΡΡΡΡΠΊΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ°; ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½Ρ ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅Π½Π½ΡΠ΅ ΠΈ ΠΊΠΎΠ»ΠΈΡΠ΅ΡΡΠ²Π΅Π½Π½ΡΠ΅ ΠΌΠ΅ΡΠΎΠ΄Ρ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΌΠΎΡΠΈΠ²ΠΎΠ² ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΉ ΠΊΠΎΠΌΠΌΡΠ½ΠΈΠΊΠ°ΡΠΈΠΈ (ΠΏΠΈΡΡΠΌΠ΅Π½Π½ΡΠ΅ ΠΎΠΏΡΠΎΡΡ ΠΈ ΡΡΡΠ½ΡΠ΅ ΠΈΠ½ΡΠ΅ΡΠ²ΡΡ ΠΏΠΎ ΠΊΠ»ΡΡΠ΅Π²ΡΠΌ ΡΠ΅ΠΌΠ°ΠΌ). Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ: Π² ΠΏΡΠΎΡΠ΅ΡΡΠ΅ ΡΠ°Π±ΠΎΡΡ ΡΠΎ ΡΠ»ΡΡΠ°ΡΠ΅Π»ΡΠΌΠΈ ΡΠ·ΡΠΊΠΎΠ²ΡΡ
ΠΊΡΡΡΠΎΠ² β ΡΡΡΠ΄Π΅Π½ΡΠ°ΠΌΠΈ Π°Π²ΡΡΡΠΈΠΉΡΠΊΠΈΡ
ΡΠ½ΠΈΠ²Π΅ΡΡΠΈΡΠ΅ΡΠΎΠ² β ΠΏΠΎΠ»ΡΡΠ΅Π½Ρ ΠΈ ΠΈΠ·ΡΡΠ΅Π½Ρ Π΄Π°Π½Π½ΡΠ΅ ΠΎ ΡΠ°ΠΊΡΠΎΡΠ°Ρ
ΠΌΠΎΡΠΈΠ²Π°ΡΠΈΠΈ ΡΡΠ°ΡΠΈΡ
ΡΡ, Π½Π°ΠΈΠ±ΠΎΠ»Π΅Π΅ Π·Π½Π°ΡΠΈΠΌΡΠ΅ Π΄Π»Ρ Π½ΠΈΡ
ΡΠ΅ΠΌΡ ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠ³ΠΎ Π΄ΠΈΠ°Π»ΠΎΠ³Π°, Π²Π°ΠΆΠ½ΡΠ΅ Π°ΡΠΏΠ΅ΠΊΡΡ ΡΡΡΡΠΊΠΎΠΉ Π³ΡΠ°ΠΌΠΌΠ°ΡΠΈΠΊΠΈ, Π° ΡΠ°ΠΊΠΆΠ΅ Π΄Π°Π½Π½ΡΠ΅ ΠΎ Π½Π°ΠΈΠ±ΠΎΠ»Π΅Π΅ Π²ΠΎΡΡΡΠ΅Π±ΠΎΠ²Π°Π½Π½ΡΡ
Π·Π½Π°Π½ΠΈΡΡ
ΠΎΠ± Π£ΠΊΡΠ°ΠΈΠ½Π΅. ΠΠ½Π°Π»ΠΈΠ· ΠΏΠΎΠ»ΡΡΠ΅Π½Π½ΡΡ
Π΄Π°Π½Π½ΡΡ
, ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½Π½ΡΠΉ Π°Π²ΡΠΎΡΠ°ΠΌΠΈ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ, ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΠ» ΠΎΠΏΡΠΈΠΌΠΈΠ·ΠΈΡΠΎΠ²Π°ΡΡ ΡΠΎΠ΄Π΅ΡΠΆΠ°Π½ΠΈΠ΅ ΡΡΠ΅Π±Π½ΠΎΠ³ΠΎ ΠΏΡΠΎΡΠ΅ΡΡΠ° ΠΈ ΠΏΠΎΠ²ΡΡΠΈΡΡ Π΅Π³ΠΎ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ. ΠΠ±ΡΡΠΆΠ΄Π΅Π½ΠΈΠ΅ ΠΈ Π·Π°ΠΊΠ»ΡΡΠ΅Π½ΠΈΡ: ΠΎΠ±ΡΡΠ΅Π½ΠΈΠ΅ ΡΡΡΡΠΊΠΎΠΌΡ ΡΠ·ΡΠΊΡ ΠΈΠ½ΠΎΡΡΡΠ°Π½ΡΠ΅Π² ΠΏΡΠ΅Π΄ΠΏΠΎΠ»Π°Π³Π°Π΅Ρ ΠΏΠ°ΡΠ°Π»Π»Π΅Π»ΡΠ½ΠΎΠ΅ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΠΈΡ
ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΉ ΠΊΠΎΠΌΠΏΠ΅ΡΠ΅Π½ΡΠΈΠΈ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΏΠΎΠ½ΠΈΠΌΠ°Π½ΠΈΡ ΠΌΠ΅ΡΡΠ½ΡΡ
ΠΊΡΠ»ΡΡΡΡΠ½ΡΡ
ΡΠ΅Π°Π»ΠΈΠΉ. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Π½ΡΠΉ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄ ΠΊ ΠΏΡΠ΅ΠΏΠΎΠ΄Π°Π²Π°Π½ΠΈΡ ΡΡΡΡΠΊΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ° ΠΊΠ°ΠΊ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΠΎΠ³ΠΎ Π² ΡΠ°ΠΌΠΊΠ°Ρ
ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΡ Π»Π΅ΡΠ½ΠΈΡ
ΡΠ·ΡΠΊΠΎΠ²ΡΡ
ΠΊΡΡΡΠΎΠ² ΠΎΠ±Π΅ΡΠΏΠ΅ΡΠΈΠ²Π°Π΅Ρ Π½Π΅ ΡΠΎΠ»ΡΠΊΠΎ ΠΏΡΠΎΡΠ½ΠΎΠ΅ ΡΡΠ²ΠΎΠ΅Π½ΠΈΠ΅ ΡΠ·ΡΠΊΠΎΠ²ΠΎΠ³ΠΎ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Π° ΡΡΡΠ΄Π΅Π½ΡΠ°ΠΌΠΈ-ΠΈΠ½ΠΎΡΡΡΠ°Π½ΡΠ°ΠΌΠΈ ΠΈ ΡΡΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎΠ΅ ΡΠ»ΡΡΡΠ΅Π½ΠΈΠ΅ ΠΈΡ
ΡΡΠΎΠ²Π½Ρ Π²Π»Π°Π΄Π΅Π½ΠΈΡ ΡΡΡΡΠΊΠΈΠΌ ΡΠ·ΡΠΊΠΎΠΌ, Π½ΠΎ ΠΈ Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠ΅ ΠΏΠΎΠ²ΡΡΠ΅Π½ΠΈΠ΅ ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΉ ΠΊΠΎΠΌΠΏΠ΅ΡΠ΅Π½ΡΠΈΠΈ ΠΎΠ±ΡΡΠ°Π΅ΠΌΡΡ
Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ ΡΠ°Π·Π½ΠΎΠΎΠ±ΡΠ°Π·Π½ΡΡ
ΠΎΠ±ΡΡΠ°ΡΡΠΈΡ
ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠΉ ΠΈ Π°ΠΊΡΠΈΠ²Π½ΠΎΠΉ ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΉ ΠΊΠΎΠΌΠΌΡΠ½ΠΈΠΊΠ°ΡΠΈΠΈ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΡΡ
ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² Ρ Π½ΠΎΡΠΈΡΠ΅Π»ΡΠΌΠΈ ΡΡΡΡΠΊΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ° ΠΏΡΠΈ ΡΠ°Π±ΠΎΡΠ΅ Π² ΡΠ°Π½Π΄Π΅ΠΌΠ΅. ΠΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ Π·Π½Π°ΡΠ΅Π½ΠΈΠ΅ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΠ΅ΡΡΡ ΡΠ΅ΠΌ, ΡΡΠΎ ΠΏΡΠ΅Π΄Π»Π°Π³Π°Π΅ΠΌΡΠΉ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄ ΠΌΠΎΠΆΠ΅Ρ Π½Π°ΠΉΡΠΈ ΡΠΈΡΠΎΠΊΠΎΠ΅ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ ΠΏΡΠΈ ΠΎΠ±ΡΡΠ΅Π½ΠΈΠΈ ΠΈΠ½ΠΎΡΡΡΠ°Π½ΡΠ΅Π² Π½Π° Π»Π΅ΡΠ½ΠΈΡ
ΡΠ·ΡΠΊΠΎΠ²ΡΡ
ΠΊΡΡΡΠ°Ρ
; ΠΏΠ΅ΡΡΠΏΠ΅ΠΊΡΠΈΠ²Ρ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΎΠ±ΡΡΠ»ΠΎΠ²Π»Π΅Π½Ρ Π½Π΅ΠΏΡΠ΅ΡΡΠ²Π½ΡΠΌ ΡΠ°Π·Π²ΠΈΡΠΈΠ΅ΠΌ Π΄Π°Π½Π½ΠΎΠΉ ΡΠΎΡΠΌΡ ΠΎΠ±ΡΡΠ΅Π½ΠΈΡ ΠΈ ΠΏΠΎΠ²ΡΡΠ΅Π½ΠΈΠ΅ΠΌ Π·Π½Π°ΡΠΈΠΌΠΎΡΡΠΈ ΠΌΠ΅ΠΆΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠΉ ΠΊΠΎΠΌΠΏΠ΅ΡΠ΅Π½ΡΠΈΠΈ Π² ΠΏΡΠ°ΠΊΡΠΈΠΊΠ΅ ΠΊΡΠ»ΡΡΡΡΠ½ΠΎΠ³ΠΎ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΡ
Theoretical backgrounds of nonlinear THz spectroscopy of semiconductor superlattices
We consider terahertz absorption and gain in a single miniband of
semiconductor superlattice subject to a bichromatic electric field in the most
general case of commensurate frequencies of the probe and pump fields. Using an
exact solution of Boltzmann transport equation, we show that in the
small-signal limit the formulas for absorption always contain two distinct
terms related to the parametric and incoherent interactions of miniband
electrons with the alternating pump field. It provides a theoretical background
for a control of THz gain without switching to the negative differential
conductivity state. For pedagogical reasons we present derivations of formulas
in detail.Comment: 14 page
Solution of the problem of catastrophic relaxation of homogeneous spin precession in superfluid He-B
The quantitative analysis of the "catastrophic relaxation" of the coherent
spin precession in He-B is presented. This phenomenon has been observed
below the temperature about 0.5 T as an abrupt shortening of the induction
signal decay. It is explained in terms of the decay instability of homogeneous
transverse NMR mode into spin waves of the longitudinal NMR. Recently the cross
interaction amplitude between the two modes has been calculated by Sourovtsev
and Fomin \cite{SF} for the so-called Brinkman-Smith configuration, i.e. for
the orientation of the orbital momentum of Cooper pairs along the magnetic
field, . In their treatment, the interaction is
caused by the anisotropy of the speed of the spin waves. We found that in the
more general case of the non-parallel orientation of corresponding to
the typical conditions of experiment, the spin-orbital interaction provides the
additional interaction between the modes. By analyzing experimental data we are
able to distinguish which contribution is dominating in different regimes.Comment: 6 pages, 1 figure, submited to JETP letter
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