Journal of Physics: Condensed Matter最新文献

{"title":"Pairing phase favored by magnetic frustration.","authors":"A Krindges, C V Morais, M Schmidt, F M Zimmer","doi":"10.1088/1361-648X/ad922b","DOIUrl":"10.1088/1361-648X/ad922b","url":null,"abstract":"<p><p>The interplay between magnetic frustration and pairing is investigated by adopting a BCS-like pairing mechanism on the frustratedJ1-J2Ising model on the square lattice. The ground-state and thermal phase transitions of the model are analyzed using a fermionic formulation within a CMF method. In this approach, the lattice system is divided into identical clusters, where the intracluster dynamic is exactly solved, and the intercluster interactions are replaced by self-consistent mean fields. We introduce a framework with two pairing couplings: an intracluster local coupling,<i>g</i>, which controls the electron pairing and its mobility within the clusters, and an intercluster coupling,<i>g</i>', which adjusts the pairing mechanism between clusters. Tuningg'/gallows evaluating how the pairing phase evolves from a weak pairing coupling between clusters (clustered system) to a strong one (g'→g, homogeneous system). In the range0⩽g'/g⩽1, we find that a gradual increase ing'/gfavors the pairing phase and induces a change in criticality. In particular, our results reveal the presence of tricriticality for a certain range ofg'/g. In addition, an increase in competing magnetic interactions weakens the magnetic orders, causing the pairing phase to occur at lower strengths of pairing interactions, especially wheng'=g. Therefore, our findings support that magnetic frustration favors the pairing phase, contributing to the onset of a superconducting state.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142622555","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}

{"title":"Finite-frequency noise, Fano factor, Δ<i>T</i>-noise and cross-correlations in double quantum dots.","authors":"A Crépieux, T Q Duong, M Lavagna","doi":"10.1088/1361-648X/ad92d4","DOIUrl":"10.1088/1361-648X/ad92d4","url":null,"abstract":"<p><p>A theoretical study on electrical current fluctuations in a double quantum dot connected to electronic reservoirs is presented, with the aim of deriving the finite-frequency noise, the Fano factor and the Δ<i>T</i>-noise. We establish a general expression for the noise in terms of Green functions in the double quantum dot and self-energies in the reservoirs. This result is then applied to model double quantum dots in various situations. For a non-interacting double quantum dot, we highlight several interesting features in the physical properties of this system. In particular, we demonstrate the possibility of obtaining a significant reduction in zero-frequency noise and Fano factor either when the system is placed in a given operating regime, or when a temperature gradient is applied between the two reservoirs, resulting in a negative Δ<i>T</i>-noise being generated. In addition, in the vicinity of honeycomb vertices, a sign change is observed in the finite-frequency cross-correlator between the two reservoirs, in contrast to what is obtained for the zero-frequency cross-correlator, which remains negative throughout the(ε1,ε2)-plane,ε1,2being the level energies in each of the two dots. By using an approximate first-level numerical approach, we finally study how the finite-frequency noise in a double quantum dot evolves under the influence of Coulomb interactions.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142622370","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}

{"title":"Distinct spectral line shifts in the Raman lines' Stokes and anti-Stokes components with temperature in the liquid crystalline system 4DBA.","authors":"Anoop Thomas, Chandan Bhai Patel, Ranjan K Singh, Kunwar Vikram","doi":"10.1088/1361-648X/ad95d4","DOIUrl":"10.1088/1361-648X/ad95d4","url":null,"abstract":"<p><p>An anomalous Raman phenomenon (ARP) refers to a scenario in which the Stokes and anti-Stokes frequencies of a Raman mode are different. Here we report that ARP introduces different line shifts in Stokes and anti-Stokes frequencies in 4-Decyloxy Benzoic acid with temperature across two thermally driven structural transitions: the smectic (S) to nematic (N) phase transition at 375 K and the nematic (N) to isotropic (I) transition at 390 K. Four Raman modes near 663, 773, 1128, and 1168 cm^-1shift towards higher frequencies (blueshift) in the Stokes frequency and towards lower frequencies (redshift) in the anti-Stokes frequency with rise in temperature near S to N phase transitions. However, in the isotropic liquid phase, both the Stokes and anti-Stokes components exhibit a redshift as temperature increases, without any noticeable distinct spectral lineshifts. Our studies bring out the importance of phonon band structure in ARP.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142686508","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}

{"title":"Exploring moiré skyrmions in twisted double bilayer and double trilayerCrI3.","authors":"Bilal Jabakhanji, Doried Ghader","doi":"10.1088/1361-648X/ad9536","DOIUrl":"10.1088/1361-648X/ad9536","url":null,"abstract":"<p><p>Moiré magnets have emerged as intriguing platforms for hosting exotic magnetic states due to the competing interactions within these materials. Recent experiments have reported noncollinear magnetic states in moiréCrI3, particularly focusing on twisted double bilayer (tDB) and double trilayer (tDT) configurations. However, atomistic simulations of moiréCrI3have largely been limited to the bilayer case. Here, we use stochastic Landau-Lifshitz-Gilbert simulations to investigate skyrmion nucleation in tDB and tDTCrI3and to estimate the threshold Dzyaloshinskii-Moriya interaction (th-DMI) required for their stabilization. Our findings show that the th-DMI decreases significantly with reduced twist angles. Above this threshold, three skyrmions nucleate at the monoclinic regions of the moiré supercell, randomly distributing across the interfacial layers and imprinting onto adjacent layers. Additionally, a substrate-induced DMI further reduces the th-DMI without affecting skyrmion localization. These results suggest that small twist angles and substrate-induced DMI can facilitate skyrmion formation in moiré structures.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142682053","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}

{"title":"Porous Haldane model: topological phase transitions and flat bands.","authors":"Fan Yang, Yi-Xuan Ling, Xu-Hui Yan, Lu Qi, Xiuyun Zhang, Ying Han, Ai-Lei He","doi":"10.1088/1361-648X/ad9723","DOIUrl":"10.1088/1361-648X/ad9723","url":null,"abstract":"<p><p>To investigate the influence of nanoholes on Chern insulators (CIs), we propose a porous Haldane model that considers the nearest-neighbor (NN) hoppings and next-NN (NNN) hoppings with staggered magnetic fluxes. This model supports multiple topological phases with different filling factors. At 2/5 filling, CI phases withC=±1,<i>C</i> = 2,C=±3,C=±4and higher-order topological insulator (HOTI) appear. At 9/20 filling, CI withC=±1,<i>C</i> = 2,<i>C</i> = 3, and HOTI phases are obtained. At half-filling, this model exhibits CI withC=±1,<i>C</i> = 2, andC=-3and HOTI phases. Unlike conventional HOTIs, these HOTI phases host gapless edge states and robust corner states which are characterized by a quantized quadrupole. Additionally, there is a topological flat band (TFB) with a flatness ratio about 13 with the NN and NNN hoppings. Based on the TFB model, we further investigate aν=1/2fractional CI state with hard-core bosons filling.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142716599","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}

{"title":"Evolution of tunable energy bandgap and magnetic anisotropy in Mn substituted ferrimagnetic nickel-chromates.","authors":"A Datta, T Sarkar, M Roy-Chowdhury, P Tiwari, H Singh, J K Dey, S Thota","doi":"10.1088/1361-648X/ad9537","DOIUrl":"10.1088/1361-648X/ad9537","url":null,"abstract":"<p><p>We report a detailed study on the composition (<i>x</i>) dependence of structural, electronic, magnetic, and optical studies of nickel chromate spinel (NiCr₂O₄) at various levels of Mn substitution at B sites. No significant structural distortion from cubic symmetry<i>Fd-</i>3m was noticed for all the compositions in the range 0 ⩽<i>x</i>⩽ 1 of Ni(Cr_1-<i>x</i>Mn<i>_x</i>)₂O₄. However, there is significant alteration in the bond angles<i>∠</i>B<i>-</i>O<i>-</i>B (90.51°-93.86°) and<i>∠</i>A<i>-</i>O<i>-</i>B (122.48°-124.90°) (both of which follow completely opposite trend with increasing<i>x</i>) and bond lengths A<i>-</i>O (1.82-1.94 Å) and B<i>-</i>O (2.02-2.08 Å). The corresponding lattice parameter (<i>a</i>) follows Vegard's law (8.32 ± 0.001 Å ⩽<i>a</i>⩽ 8.45 ± 0.001Å). The electronic structure determined from the<i>x-</i>ray photoelectron spectroscopy reveals the divalent nature of Ni (with spin-orbit splitting energy Δ ∼ 17.62 eV). While the Cr and Mn are stable with trivalent electronic states having Δ<i>=</i>8 and 11.7 eV, respectively. These results are in consonance with the cationic distribution (Ni)_A[(Cr_1-<i>x</i>Mn<i>_x</i>)₂]_BO₄obtained from the Rietveld refinement analysis. Interestingly, the current series shows a direct bandgap (<i>E</i>_G) semiconducting nature in which<i>E</i>_Gvaries from 1.16 to 2.40 eV within the range of<i>x</i>= 0.85-0. Such variation of<i>E</i>_G(<i>x</i>) is consistent with the compositional variation of the crystal structure data with anomalous change between<i>x</i>= 0.25 and 0.6. Beyond this range, the<i>E</i>_gmode (140 cm^-1) in Raman spectra arising from Mn-O octahedral decreases continuously and vanishes at higher Mn concentrations. Our analysis shows that all the investigated compounds show long-range ferrimagnetic ordering below the Néel temperature,<i>T</i>_FNdue to the unequal magnetic moments of the cations. However, both the ordering temperature<i>T</i>_FNand saturation magnetization (<i>M</i>_S) increases progressively from 73.3 K (1500 emu mol^-1) to 116 K (3600 emu mol^-1) with increasing the Mn content from 0 to 1, yet the maximum anisotropy (<i>H_K</i>~4.5 kOe,<i>K</i>₁~2.5 × 10⁴erg cc^-1) shows an opposite trend with<i>x</i>. Such variation is ascribed to the altered magnetic superexchange interactions between the cations located at A and B sites following the trend<i>J</i>_BB><i>J</i>_AB><i>J</i>_AA, (<i>J</i>_BB/<i>k</i>_B=13.36 K).</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142682086","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}

{"title":"Lateral size dependence of photoconductivity in TMD networks.","authors":"D Olaya-Cortes, L Ramos, T Rubio, J P Pabon, Y Hernandez","doi":"10.1088/1361-648X/ad965a","DOIUrl":"10.1088/1361-648X/ad965a","url":null,"abstract":"<p><p>Photoconductivity is an important feature of semiconductors that finds major attention in the fields of solar cells, hydrogen and oxygen evolution reactions, and photodetectors. This feature involves a change of density of charge carriers induced by light, which is dependent on the generation of light-induced carriers and the recombination of excitons. This phenomenon has been observed in transition metal dichalcogenides (TMDs) since 2010; however, when printing such materials on flexible substrates, they form networks that would exhibit distinct transport characteristics compared to isolated TMDs crystals. In this work, TMD nanosheets are printed by vacuum filtering and their photoconductivity was measured by using a xenon lamp inside an obscure chamber. Molybdenum disulfide-based devices show higher responsivity as compared with tungsten disulfide devices, which is attributed to an increased light absorption and hydroxyl groups attached to the surface of the MoS₂networks that enhance the photoconductivity by increasing the carrier lifetimes. Furthermore, the responsivity of the devices behaves similarly to the conductivity, which is modeled as networks of pairs of nanosheets and junctions through percolative paths. Finally, this is the first report that shows that the response time of the devices increases with lateral size.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142693205","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}

{"title":"An unusual phase transition in a non-Hermitian Su-Schrieffer-Heeger model.","authors":"A Niveth, S Karthiga, M Senthilvelan","doi":"10.1088/1361-648X/ad9448","DOIUrl":"10.1088/1361-648X/ad9448","url":null,"abstract":"<p><p>This article studies a non-Hermitian Su-Schrieffer-Heeger model which has periodically staggered Hermitian and non-Hermitian dimers. The changes in topological phases of the considered chiral symmetric model with respect to the introduced non-Hermiticity are studied where we find that the system supports only complex eigenspectra for all values of<i>u</i> ≠ 0 and it stabilizes only non-trivial insulating phase for higher loss-gain strength. Even if the system acts as a trivial insulator in the Hermitian limit, the increase in loss-gain strength induces phase transition to non-trivial insulating phase through a (gapless) semi-metallic phase. Interesting phenomenon is observed in the case where Hermitian system acts as a non-trivial insulator. In such a situation, the introduced non-Hermiticity neither leaves the non-trivial phase undisturbed nor induces switching to trivial phase. Rather, it shows transition from non-trivial insulating phase to the same where it is mediated by the stabilization of (non-trivial) semi-metallic phase. This unusual transition between the non-trivial insulating phases through non-trivial semi-metallic phase gives rise to a question regarding the topological states of the system under open boundary conditions. So, we analyze the possibility of stable edge states in these two non-trivial insulating phases and check the characteristic difference between them. In addition, we study the nature of topological states in the case of non-trivial gapless (semi-metallic) region.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142667507","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}

{"title":"Fluids with power-law repulsion: Hyperuniformity and energy fluctuations.","authors":"H Diamant, E C Oǧuz","doi":"10.1088/1361-648X/ad912d","DOIUrl":"10.1088/1361-648X/ad912d","url":null,"abstract":"<p><p>We revisit the equilibrium statistical mechanics of a classical fluid of point-like particles with repulsive power-law pair interactions, focusing on density and energy fluctuations at finite temperature. Such long-range interactions, decaying with inter-particle distance<i>r</i>as1/rsin<i>d</i>dimensions, are known to fall into two qualitatively different categories. For<i>s</i> < <i>d</i>('strongly' long-range interactions) there are screening of correlations and suppression of large-wavelength density fluctuations (hyperuniformity). These effects eliminate density modes with arbitrarily large energy. For<i>s</i> > <i>d</i>('weakly' long-range interactions) screening and hyperuniformity do not occur. Using scaling arguments, variational analysis, and Monte Carlo simulations, we find another qualitative distinction. Fors⩾d/2the strong repulsion at short distances leads to enhanced small-wavelength density fluctuations, decorrelating particle positions. This prevents indefinitely negative entropy and large energy fluctuations. The distinct behaviors fors⩾d/2ands<d/2give rise to qualitatively different dependencies of the entropy, heat capacity, and energy fluctuations on temperature and density. We investigate the effect of introducing an upper cutoff distance in the pair-potential. The effect of the cutoff on energy fluctuations is strong fors<d/2and negligible fors⩾d/2.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142622414","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}

{"title":"Spin injection from a magnetically near-compensated state in GdFeCo and inverse spin Hall effect in electron-hole compensated metal YH₂.","authors":"Ikuo Yamazaki, Yukihiro Koinuma, Tatsuro Hanajiri, Pham Van Thach, Sina Ranjbar, Satoshi Sumi, Hiroyuki Awano, Osamu Nakamura, Shigehiko Hasegawa, Masamichi Sakai","doi":"10.1088/1361-648X/ad9371","DOIUrl":"10.1088/1361-648X/ad9371","url":null,"abstract":"<p><p>Rare-earth-transition-metal (RE-TM) ferrimagnets are excellent materials for spin encode/decode operations via spin transport in nonmagnetic regions. This superior performance stems from two key factors. First, the antiferromagnetic coupling between RE4f and TM3d sublattices reduces both the spin-transfer-torque switching time and inter-device magnetic-coupling. Second, the RE-TM ferrimagnets function as spin injectors/ejectors, with the TM3d sublattice solely responsible for carrier spin polarization (<i>p</i>), similar to conventional ferromagnetic metals. We performed spin transport experiments using the sign change of<i>p</i>in RE-TM, which exhibits a positive value above the magnetization compensation temperature and a negative value below it. We measured temperature dependencies of the transverse resistances (RT) of electron-hole compensated metal YH₂under out-of-plane spin-polarized current injection/ejection from GdFeCo (Gd:Fe:Co = 25:66:9). The abrupt change in loop polarity of the out-of-plane field dependence ofRTin YH₂between 290 and 300 K, which aligns with the out-of-field curve of the polar Kerr rotation in GdFeCo electrodes, strongly suggests that the observedRTresults from the inverse spin Hall effect (ISHE) in YH₂. We analytically formulated ISHE in terms of the electron and hole spin currents injected from the spin sources, enabling regression analysis to assess the spin transport characteristics of a GdFeCo/YH₂/GdFeCo magnetic double heterostructure. To explain the observed Hall voltages, enhancements in both the spin diffusion length of YH₂and the spin injection efficiency are necessary.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142639263","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}