JETP LettersPub Date : 2026-06-18DOI: 10.1134/S0021364026601016
I. V. Panyukov, E. S. Andrianov
{"title":"On Measurement of the Second-Order Coherence of Light–Matter Bose–Einstein Condensates with a Single Detector","authors":"I. V. Panyukov, E. S. Andrianov","doi":"10.1134/S0021364026601016","DOIUrl":"10.1134/S0021364026601016","url":null,"abstract":"<p>The second-order autocorrelation function, <span>({{g}^{{(2)}}}(0))</span>, measured in the Hanbury Brown–Twiss scheme is the strong indicator separating the thermal (incoherent) from the coherent state of light emitted by lasers or photon or polariton condensates. Consequently, <span>({{g}^{{(2)}}}(0))</span> can be used to determine if the Bose–Einstein condensate forms in the system. The fast dynamics of non-equilibrium light–matter Bose–Einstein condensate make implementing the Hanbury Brown–Twiss scheme challenging and expensive. A good time resolution requires single-photon detectors operating at cryogenic temperatures. An alternative approach to measuring <span>({{g}^{{(2)}}}(0))</span>, taken in many experiments, is to rely on the scheme with a single detector and measure the intensity fluctuations to directly obtain <span>({{g}^{{(2)}}}(0))</span>. In this paper, we show that the Hanbury Brown–Twiss scheme and the single detector scheme are not equivalent in the general case because we cannot directly use the intensity fluctuations measured in the single detector scheme to obtain <span>({{g}^{{(2)}}}(0))</span> of light emitted by a multi-mode system. Nevertheless, we develop a method allowing for the reconstruction of <span>({{g}^{{(2)}}}(0))</span> from the measurements in the single detector scheme for a multi-mode system with fast thermalization and illustrate it for a special case of non-equilibrium light–matter Bose–Einstein condensate.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 12","pages":"808 - 815"},"PeriodicalIF":1.1,"publicationDate":"2026-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364026601016.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-31DOI: 10.1134/S0021364026600679
D. A. Kurmachev, Z. D. Kvon, N. N. Mikhailov
{"title":"Fluctuating Conductance of Mesoscopic Conductors Based on a Highly Disordered Two-Dimensional Semimetal in an HgTe Quantum Well","authors":"D. A. Kurmachev, Z. D. Kvon, N. N. Mikhailov","doi":"10.1134/S0021364026600679","DOIUrl":"10.1134/S0021364026600679","url":null,"abstract":"<p>Fluctuations of dissipative and Hall conductance in submicron conductors based on highly disordered HgTe quantum wells with a semimetallic energy spectrum have been investigated for the first time, and a comparative analysis of their behavior with universal conductance fluctuations in the electron metal state has been carried out. It has been concluded that the highly disordered two-dimensional semimetal in the HgTe quantum well is characterized by the existence of anomalous fluctuations of the dissipative and Hall conductance, whose nature is not related to the well-known universal conductance fluctuations in a disordered metal.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 8","pages":"544 - 547"},"PeriodicalIF":1.3,"publicationDate":"2026-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364026600679.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148061235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-31DOI: 10.1134/S0021364026600631
N. A. Grigoryeva, A. A. Eliseev, P. E. Kazin, A. A. Semina, A. P. Chumakov, A. A. Eliseev, S. V. Grigoriev
{"title":"Synchrotron Small-Angle Scattering Study of Concentrated Ferrofluids Based on Strontium Hexaferrite Nanoparticles in a Magnetic Field","authors":"N. A. Grigoryeva, A. A. Eliseev, P. E. Kazin, A. A. Semina, A. P. Chumakov, A. A. Eliseev, S. V. Grigoriev","doi":"10.1134/S0021364026600631","DOIUrl":"10.1134/S0021364026600631","url":null,"abstract":"<p>The structural composition of a concentrated aqueous solution of 50 × 5-nm plate-shaped ferrimagnetic nanoparticles of strontium hexaferrite (SrFe<sub>12</sub>O<sub>19</sub>) in a magnetic field has been studied using synchrotron small-angle scattering. A characteristic feature of these magnetic fluids is the formation of randomly oriented periodic structures even in the absence of a magnetic field. Two-dimensional maps of the synchrotron small-angle scattering intensity show isotropic scattering in zero field and growth of a series of diffraction reflections along the direction of the applied magnetic field at <i>Q</i> = <i>nq</i><sub><i>b</i></sub>, where <i>q</i><sub><i>b</i></sub> ≈ 0.226 nm<sup>–1</sup> (period ~27.8 nm), which is due to the formation and orientation of nanoplate chains along the field. The analysis of the broadening of diffraction reflections has shown that the coherence of the chains even in extremely high magnetic fields, is 8–10 periods. However, this does not limit the length of the chain, but is due to disorientation and the dispersion of particle sizes. The degree of orientation of the segments is determined by the azimuthal width and intensity of the Bragg peaks. The chains of nanoplates are rotated toward the field direction with the field increase in the range <i>H</i> < 70 Oe (isotropic fluid–one-dimensional nematic transition); they form an intermediate state in the range 70 Oe < <i>H</i> < 300 Oe and a smectic (three-dimensional) phase at <i>H</i> > 300 Oe. The intermediate state is characterized by a logarithmic dependence of the intensity and width of the Bragg peak on the magnetic field, which presumably indicates a self-organized criticality state of the magnetic colloid.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 8","pages":"548 - 555"},"PeriodicalIF":1.3,"publicationDate":"2026-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364026600631.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148061240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-31DOI: 10.1134/S0021364026600904
V. A. Tomilin, A. M. Rostom, L. V. Il’ichev
{"title":"Geometric Phase of the Two-Particle Bethe Wavefunction","authors":"V. A. Tomilin, A. M. Rostom, L. V. Il’ichev","doi":"10.1134/S0021364026600904","DOIUrl":"10.1134/S0021364026600904","url":null,"abstract":"<p>The problem of generating a geometric phase in a system of a pair of interacting bosons confined in a spatial configuration of a narrow ring with a localized potential defect has been considered. The geometric phase arises due to variation of defect parameters. The interaction between particles has been taken into account within the Lieb–Liniger model. The energy spectrum has been found and its dependence on the problem parameters has been described. It has been shown that the interaction leads to an increase in the geometric phase for the selected contour of variation of the defect parameters. The motivation is dictated by the previously proposed ideas of a quantum gyroscope and a quantum accelerometer based on atomic Bose–Einstein condensates.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 8","pages":"566 - 572"},"PeriodicalIF":1.3,"publicationDate":"2026-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364026600904.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148061236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-31DOI: 10.1134/S0021364026600849
A. A. Maksimov, I. I. Tartakovskii, N. A. Abdullaev, Z. S. Aliev, N. T. Mamedov
{"title":"Raman Scattering and Spin–Phonon Coupling in Crystals of the Magnetic Topological Insulator MnBi2Te4","authors":"A. A. Maksimov, I. I. Tartakovskii, N. A. Abdullaev, Z. S. Aliev, N. T. Mamedov","doi":"10.1134/S0021364026600849","DOIUrl":"10.1134/S0021364026600849","url":null,"abstract":"<p>Raman spectra of MnBi<sub>2</sub>Te<sub>4</sub> magnetic topological insulator crystals have been experimentally studied at temperatures from liquid helium to room temperature. Features of the behavior of a phonon with the <span>(A_{{1g}}^{2})</span> symmetry in MnBi<sub>2</sub>Te<sub>4</sub> at temperatures below and above the antiferromagnetic phase transition temperature has been discovered and studied in detail for the first time. These features demonstrate the strong influence of the spin–phonon interaction with the magnetic degrees of freedom of the topological insulator on the frequency and intensity of the phonon.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 8","pages":"535 - 539"},"PeriodicalIF":1.3,"publicationDate":"2026-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364026600849.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148061239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-31DOI: 10.1134/S0021364026600771
R. Kh. Zhukavin, V. D. Kukotenko, P. A. Bushuikin, Yu. Yu. Choporova, N. D. Osintseva, K. A. Kovalevsky, V. V. Tsyplenkov, V. V. Gerasimov, N. Dessmann, N. V. Abrosimov, V. N. Shastin
{"title":"Photon Echo in Uniaxially Stressed Germanium with Antimony Donors","authors":"R. Kh. Zhukavin, V. D. Kukotenko, P. A. Bushuikin, Yu. Yu. Choporova, N. D. Osintseva, K. A. Kovalevsky, V. V. Tsyplenkov, V. V. Gerasimov, N. Dessmann, N. V. Abrosimov, V. N. Shastin","doi":"10.1134/S0021364026600771","DOIUrl":"10.1134/S0021364026600771","url":null,"abstract":"<p>In an <i>n</i>-Ge crystal uniaxially stressed along the [111] crystallographic direction, the photon echo effect has been demonstrated, and the coherence relaxation time <i>T</i><sub>2</sub> has been estimated at ~300 ps. Nonlinear polarization leading to the effect appears due to antimony donors. Uniaxial deformation of the crystal, which is responsible for valley splitting of the donor states, significantly increases the coherence time and leads to the possibility of implementing the effect.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 8","pages":"529 - 534"},"PeriodicalIF":1.3,"publicationDate":"2026-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364026600771.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148061238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-31DOI: 10.1134/S0021364026600576
G. E. Rizaev, M. V. Levus, T. A. Dick, L. V. Seleznev
{"title":"Forward and Backward Lasing from an Ultraviolet Filament in Argon","authors":"G. E. Rizaev, M. V. Levus, T. A. Dick, L. V. Seleznev","doi":"10.1134/S0021364026600576","DOIUrl":"10.1134/S0021364026600576","url":null,"abstract":"<p>Lasing of atomic argon induced by filamentation of ultraviolet femtosecond laser pulses at 250 nm has been experimentally studied. Emission on the <span>(4p to 4s)</span> transitions (763.5, 801.5, and 842.5 nm) is observed to propagate both in the forward direction, along the laser pulse, and in the backward direction. An energy threshold of ~90 μJ is identified, above which the emission intensity increases sharply. The forward lasing energy exceeds the backward one by nearly an order of magnitude. The spatial profile of the emission consists of concentric rings with an angular divergence below 10 mrad. Based on estimates of the gain length, the gain coefficient of the medium is approximately 0.1 cm<sup>–1</sup>.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 8","pages":"540 - 543"},"PeriodicalIF":1.3,"publicationDate":"2026-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148061234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-31DOI: 10.1134/S0021364026600655
I. O. Kinyaevskiy, M. V. Ionin, A. V. Koribut, Ya. V. Grudtsyn, Yu. M. Klimachev, D. V. Badikov
{"title":"“Two-Color” Difference Frequency Generation Due to Type-I and Type-II Phase Matching in a Nonlinear BaGa2GeS6 Crystal Pumped by Femtosecond Ti:Sapphire Laser Pulses","authors":"I. O. Kinyaevskiy, M. V. Ionin, A. V. Koribut, Ya. V. Grudtsyn, Yu. M. Klimachev, D. V. Badikov","doi":"10.1134/S0021364026600655","DOIUrl":"10.1134/S0021364026600655","url":null,"abstract":"<p>The difference frequency generation of femtosecond Ti:sapphire laser pulses in the wavelength range of 5‒10 μm in a 2.46-mm-long nonlinear BaGa<sub>2</sub>GeS<sub>6</sub> crystal has been experimentally studied. The energy of difference frequency radiation pulses has reached 23 μJ. It has been found that “two-color” difference frequency generation occurs in BaGa<sub>2</sub>GeS<sub>6</sub> simultaneously due to type-I and type-II phase matching, leading to the appearance of two ~0.5 μm wide spectral bands in the mid-infrared range separated by 1.5–2 μm. The influence of the polar and azimuthal angles of BaGa<sub>2</sub>GeS<sub>6</sub> on the spectral and energy characteristics of the two-color radiation has been demonstrated. The resulting two-color radiation can be used for remote gas analysis by the differential absorption method.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 8","pages":"514 - 520"},"PeriodicalIF":1.3,"publicationDate":"2026-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148061237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-12DOI: 10.1134/S0021364026600886
M. S. Shustin, M. N. Potkina, A. D. Fedoseev, D. M. Dzebisashvili
{"title":"Analytical Profiles of Skyrmion Bags","authors":"M. S. Shustin, M. N. Potkina, A. D. Fedoseev, D. M. Dzebisashvili","doi":"10.1134/S0021364026600886","DOIUrl":"10.1134/S0021364026600886","url":null,"abstract":"<p>Topologically nontrivial localized 2D magnetic states with high topological charge (<span>({text{|}}Q{text{|}} > 1)</span>) have attracted significant attention in the last decade, driven by their experimental and numerical discovery. In this work, we propose an analytical ansatz capable of describing both axially symmetric <span>(kpi )</span>-skyrmions and <span>({{C}_{g}})</span>-symmetric skyrmion bags, with a straightforward extension to a wide range of other multi-skyrmion textures. By comparing with numerical micromagnetic simulations, we show that the proposed ansatz describes skyrmion bags with accuracy sufficient for practical applications.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 10","pages":"706 - 713"},"PeriodicalIF":1.1,"publicationDate":"2026-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364026600886.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148349770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
JETP LettersPub Date : 2026-05-12DOI: 10.1134/S0021364025608437
E. V. Luschevskaya, O. V. Teryaev, E. A. Dorenskaya, S. Y. Alimagomedova, Z. V. Khaidukov
{"title":"Magnetic Moment of K*0 Mesons in SU(3) Lattice Gauge Theory","authors":"E. V. Luschevskaya, O. V. Teryaev, E. A. Dorenskaya, S. Y. Alimagomedova, Z. V. Khaidukov","doi":"10.1134/S0021364025608437","DOIUrl":"10.1134/S0021364025608437","url":null,"abstract":"<p>We calculate the energies and investigate the physical properties of the neutral vector <i>K</i>*<sup>0</sup> mesons in external strong abelian magnetic field. We explore how the magnetic moment of the neutral vector <i>K</i>* mesons depends on the ratio of the bare strange and light quark masses <span>({{m}_{s}}{text{/}}{{m}_{d}})</span>. The extrapolation of <span>(g)</span>-factor to the physical pion mass was performed at <span>({{m}_{s}}{text{/}}{{m}_{d}} = 20)</span>. We also calculated the magnetic dipole polarizability of <i>K</i>*<sup>0</sup>-meson for the <span>({{s}_{z}} = - 1)</span> case.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"123 10","pages":"653 - 660"},"PeriodicalIF":1.1,"publicationDate":"2026-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364025608437.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148349721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}