E. A. Martínez, A. M. Lucero, E. D. Cantero, N. Biškup, A. Orte, E. A. Sánchez, M. Romera, N. M. Nemes, J. L. Martínez, M. Varela, O. Grizzi, F. Y. Bruno
The two-dimensional electron gas (2DEG) found in KTaO3-based interfaces has garnered attention due to its remarkable electronic properties. In this study, we investigated the conducting system embedded at the Si3N4/Al//KTO(110) heterostructure. We demonstrate that the Al/KTO interface supports a conducting system, with the Si3N4 passivation layer acting as a barrier to oxygen diffusion, enabling ex-situ characterization. Our findings reveal that the mobility and carrier density of the system can be tuned by varying the Al layer thickness. Using scanning transmission electron microscopy, electron energy-loss spectroscopy, X-ray photoemission spectroscopy, and time-of-flight secondary ion mass spectrometry, we characterized the structural and chemical composition of the interface. We found that the Al layer fully oxidizes into AlOx, drawing oxygen from the KTaO3 substrate. The oxygen depletion zone extends 3-5 nm into the substrate and correlates to the Al thickness. Heterostructures with thicker Al layers exhibit higher carrier densities but lower mobilities, likely due to interactions with the oxygen vacancies that act as scattering centers. These findings highlight the importance of considering the effect and extent of the oxygen depletion zone when designing and modeling two-dimensional electron systems in complex oxides.
{"title":"High stability 2D electron gases formed in Si3N4/Al//KTaO3 heterostructures: synthesis and in-depth interfacial characterization","authors":"E. A. Martínez, A. M. Lucero, E. D. Cantero, N. Biškup, A. Orte, E. A. Sánchez, M. Romera, N. M. Nemes, J. L. Martínez, M. Varela, O. Grizzi, F. Y. Bruno","doi":"arxiv-2409.11893","DOIUrl":"https://doi.org/arxiv-2409.11893","url":null,"abstract":"The two-dimensional electron gas (2DEG) found in KTaO3-based interfaces has\u0000garnered attention due to its remarkable electronic properties. In this study,\u0000we investigated the conducting system embedded at the Si3N4/Al//KTO(110)\u0000heterostructure. We demonstrate that the Al/KTO interface supports a conducting\u0000system, with the Si3N4 passivation layer acting as a barrier to oxygen\u0000diffusion, enabling ex-situ characterization. Our findings reveal that the\u0000mobility and carrier density of the system can be tuned by varying the Al layer\u0000thickness. Using scanning transmission electron microscopy, electron\u0000energy-loss spectroscopy, X-ray photoemission spectroscopy, and time-of-flight\u0000secondary ion mass spectrometry, we characterized the structural and chemical\u0000composition of the interface. We found that the Al layer fully oxidizes into\u0000AlOx, drawing oxygen from the KTaO3 substrate. The oxygen depletion zone\u0000extends 3-5 nm into the substrate and correlates to the Al thickness.\u0000Heterostructures with thicker Al layers exhibit higher carrier densities but\u0000lower mobilities, likely due to interactions with the oxygen vacancies that act\u0000as scattering centers. These findings highlight the importance of considering\u0000the effect and extent of the oxygen depletion zone when designing and modeling\u0000two-dimensional electron systems in complex oxides.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"160 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We show that the two-dimensional $mathbb{Z}_2$ invariant for time-reversal invariant insulators can be formulated in terms of the boundary-condition dependence of the ground state wavefunction for both non-interacting and strongly-correlated insulators. By introducing a family of quasi-single particle states associated to the many-body ground state of an insulator, we show that the $mathbb{Z}_2$ invariant can be expressed as the integral of a certain Berry connection over half the space of boundary conditions, providing an alternative expression to the formulations that appear in [Lee et al., Phys. Rev. Lett. $textbf{100}$, 186807 (2008)]. We show the equivalence of the different many-body formulations of the invariant, and show how they reduce to known band-theoretic results for Slater determinant ground states. Finally, we apply our results to analytically calculate the invariant for the Kane-Mele model with nonlocal (orbital) Hatsugai-Kohmoto (HK) interactions. This rigorously establishes the topological nontriviality of the Kane-Mele model with HK interactions, and represents one of the few exact calculations of the $mathbb{Z}_2$ invariant for a strongly-interacting system.
{"title":"Computing the $mathbb{Z}_2$ Invariant in Two-Dimensional Strongly-Correlated Systems","authors":"Sounak Sinha, Barry Bradlyn","doi":"arxiv-2409.12120","DOIUrl":"https://doi.org/arxiv-2409.12120","url":null,"abstract":"We show that the two-dimensional $mathbb{Z}_2$ invariant for time-reversal\u0000invariant insulators can be formulated in terms of the boundary-condition\u0000dependence of the ground state wavefunction for both non-interacting and\u0000strongly-correlated insulators. By introducing a family of quasi-single\u0000particle states associated to the many-body ground state of an insulator, we\u0000show that the $mathbb{Z}_2$ invariant can be expressed as the integral of a\u0000certain Berry connection over half the space of boundary conditions, providing\u0000an alternative expression to the formulations that appear in [Lee et al., Phys.\u0000Rev. Lett. $textbf{100}$, 186807 (2008)]. We show the equivalence of the\u0000different many-body formulations of the invariant, and show how they reduce to\u0000known band-theoretic results for Slater determinant ground states. Finally, we\u0000apply our results to analytically calculate the invariant for the Kane-Mele\u0000model with nonlocal (orbital) Hatsugai-Kohmoto (HK) interactions. This\u0000rigorously establishes the topological nontriviality of the Kane-Mele model\u0000with HK interactions, and represents one of the few exact calculations of the\u0000$mathbb{Z}_2$ invariant for a strongly-interacting system.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"abs/2206.05846 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Liam Watson, Iolanda Di Bernardo, James Blyth, Benjamin Lowe, Thi-Hai-Yen Vu, Daniel McEwen, Mark T. Edmonds, Anton Tadich, Michael S. Fuhrer
The strong electron-electron interaction in transition metal dichalcogenides (TMDs) gives rise to phenomena such as strong exciton and trion binding and excitonic condensation, as well as large negative exchange and correlation contributions to the electron energies, resulting in negative electronic compressibility. Here we use angle-resolved photoemission spectroscopy to demonstrate a striking effect of negative electronic compressibility in semiconducting TMD MoS2 on the charge transfer to and from a partial overlayer of monolayer semimetallic WTe2. We track the changes in binding energy of the valence bands of both WTe2 and MoS2 as a function of surface transfer doping with donor (K) and acceptor (F4-TCNQ) species. Donor doping increases the binding energy of the MoS2 valence band, as expected, while counterintuitively reducing the binding energy of the WTe2 valence bands and core levels. The inverse effect is observed for acceptor doping, where a typical reduction in the MoS2 binding energies is accopanied by an unexpected increase in those of WTe2. The observations imply a reversal of the expected charge transfer; donor (acceptor) deposition decreases (increases) the carrier density in the WTe2 adlayer. The charge transfer reversal is a direct consequence of the negative electronic compressibility of the MoS2 surface layer, for which addition (subtraction) of charge leads to attraction (repulsion) of further charge from neighbouring layers. These findings highlight the importance of many-body interactions for the electrons in transition metal dichalcogenides and underscore the potential for exploring strongly correlated quantum states in two-dimensional semiconductors.
{"title":"Reversal of charge transfer doping on the negative electronic compressibility surface of MoS2","authors":"Liam Watson, Iolanda Di Bernardo, James Blyth, Benjamin Lowe, Thi-Hai-Yen Vu, Daniel McEwen, Mark T. Edmonds, Anton Tadich, Michael S. Fuhrer","doi":"arxiv-2409.11886","DOIUrl":"https://doi.org/arxiv-2409.11886","url":null,"abstract":"The strong electron-electron interaction in transition metal dichalcogenides\u0000(TMDs) gives rise to phenomena such as strong exciton and trion binding and\u0000excitonic condensation, as well as large negative exchange and correlation\u0000contributions to the electron energies, resulting in negative electronic\u0000compressibility. Here we use angle-resolved photoemission spectroscopy to\u0000demonstrate a striking effect of negative electronic compressibility in\u0000semiconducting TMD MoS2 on the charge transfer to and from a partial overlayer\u0000of monolayer semimetallic WTe2. We track the changes in binding energy of the\u0000valence bands of both WTe2 and MoS2 as a function of surface transfer doping\u0000with donor (K) and acceptor (F4-TCNQ) species. Donor doping increases the\u0000binding energy of the MoS2 valence band, as expected, while counterintuitively\u0000reducing the binding energy of the WTe2 valence bands and core levels. The\u0000inverse effect is observed for acceptor doping, where a typical reduction in\u0000the MoS2 binding energies is accopanied by an unexpected increase in those of\u0000WTe2. The observations imply a reversal of the expected charge transfer; donor\u0000(acceptor) deposition decreases (increases) the carrier density in the WTe2\u0000adlayer. The charge transfer reversal is a direct consequence of the negative\u0000electronic compressibility of the MoS2 surface layer, for which addition\u0000(subtraction) of charge leads to attraction (repulsion) of further charge from\u0000neighbouring layers. These findings highlight the importance of many-body\u0000interactions for the electrons in transition metal dichalcogenides and\u0000underscore the potential for exploring strongly correlated quantum states in\u0000two-dimensional semiconductors.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Avital Fried, Ouriel Gotesdyner, Irena Feldman, Amit Kanigel, Amos Sharoni
The ramp reversal memory (RRM) is a non-volatile memory effect previously observed in correlated oxides exhibiting temperature-driven metal-insulator transitions (MITs). In essence, when a system displaying RRM is heated to a specific temperature within the MIT regime - where metallic and insulating domains coexist - and then cooled by reversing the temperature ramp, the resistance increases in the subsequent heating cycle. Crucially, this increase occurs only in the vicinity of the reversal temperature, indicating that the system 'remembers' this temperature. However, this memory is erased in the next heating loop. While such an effect could potentially manifest in various systems, to date, it has only been reported in thin films of correlated transition metal oxides, including VO2, V2O3, and NdNiO3. In this work, we report the observation of RRM in macroscopic crystals of the layered material 1T-TaS2, which undergoes an MIT near 190 K along charge-density wave transitions. Our findings provide compelling evidence that RRM is a general phenomenon, extending beyond the previously studied oxides. Interestingly, the RRM in TaS2 displays significantly different characteristics: it is observed when reversing from cooling to heating (as opposed to heating to cooling), and its magnitude - representing the 'strength' of the memory - is nearly an order of magnitude larger than in correlated oxides. While we discuss potential mechanisms for the RRM in TaS2, a comprehensive first-principles model is still lacking. We hope that this study will prompt further investigation into the underlying mechanisms of ramp reversal memory, enhancing our understanding of this intriguing phenomenon.
{"title":"Ramp reversal memory in bulk crystals of 1T-TaS2","authors":"Avital Fried, Ouriel Gotesdyner, Irena Feldman, Amit Kanigel, Amos Sharoni","doi":"arxiv-2409.11977","DOIUrl":"https://doi.org/arxiv-2409.11977","url":null,"abstract":"The ramp reversal memory (RRM) is a non-volatile memory effect previously\u0000observed in correlated oxides exhibiting temperature-driven metal-insulator\u0000transitions (MITs). In essence, when a system displaying RRM is heated to a\u0000specific temperature within the MIT regime - where metallic and insulating\u0000domains coexist - and then cooled by reversing the temperature ramp, the\u0000resistance increases in the subsequent heating cycle. Crucially, this increase\u0000occurs only in the vicinity of the reversal temperature, indicating that the\u0000system 'remembers' this temperature. However, this memory is erased in the next\u0000heating loop. While such an effect could potentially manifest in various\u0000systems, to date, it has only been reported in thin films of correlated\u0000transition metal oxides, including VO2, V2O3, and NdNiO3. In this work, we\u0000report the observation of RRM in macroscopic crystals of the layered material\u00001T-TaS2, which undergoes an MIT near 190 K along charge-density wave\u0000transitions. Our findings provide compelling evidence that RRM is a general\u0000phenomenon, extending beyond the previously studied oxides. Interestingly, the\u0000RRM in TaS2 displays significantly different characteristics: it is observed\u0000when reversing from cooling to heating (as opposed to heating to cooling), and\u0000its magnitude - representing the 'strength' of the memory - is nearly an order\u0000of magnitude larger than in correlated oxides. While we discuss potential\u0000mechanisms for the RRM in TaS2, a comprehensive first-principles model is still\u0000lacking. We hope that this study will prompt further investigation into the\u0000underlying mechanisms of ramp reversal memory, enhancing our understanding of\u0000this intriguing phenomenon.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Khanenko, D. Hafner, K. Semeniuk, J. Banda, T. Luehmann, F. Baertl, T. Kotte, J. Wosnitza, G. Zwicknagl, C. Geibel, J. F. Landaeta, S. Khim, E. Hassinger, M. Brando
Unconventional superconductivity in heavy-fermion systems appears often near magnetic quantum critical points (QCPs). This seems to be the case also for CeRh2As2 (Tc $approx$ 0.31 K). CeRh2As2 shows two superconducting (SC) phases, SC1 and SC2, for a magnetic field along the c axis of the tetragonal unit cell, but only the SC1 phase is observed for a field along the basal plane. Furthermore, another ordered state (phase-I) is observed below T0 $approx$ 0.48 K whose nature is still unclear: Thermodynamic and magnetic measurements pointed to a non magnetic multipolar state, but recent $mu$SR and NQR/NMR experiments have clearly detected antiferromagnetic (AFM) order below T0 . Also, quasi-two-dimensional AFM fluctuations were observed in NMR and neutron-scattering experiments above T0. The proximity of a QCP is indicated by non-Fermi-liquid (NFL) behavior observed above the ordered states in both specific heat $C(T)/T propto T^{-0.6}$ and resistivity $rho(T) propto T^{0.5}$. These T-dependencies are not compatible with any generic AFM QCP. Because of the strong magnetic-field anisotropy of both the SC phase and phase I, it is possible to study a field-induced SC QCP as well a phase-I QCP by varying the angle $alpha$ between the field and the c axis. Thus, by examining the behavior of the electronic specific-heat coefficient C(T)/T across these QCPs, we can determine which phase is associated with the NFL behavior. Here, we present low-temperature specific-heat measurements taken in a magnetic field as high as 21 T applied at several angles $alpha$. We observe that the NFL behavior does very weakly depend on the field and on the angle $alpha$, a result that is at odd with that observations in standard magnetic QCPs. This suggests a nonmagnetic origin of the quantum critical fluctuations.
{"title":"Origin of the non-Fermi-liquid behavior in CeRh2As2","authors":"P. Khanenko, D. Hafner, K. Semeniuk, J. Banda, T. Luehmann, F. Baertl, T. Kotte, J. Wosnitza, G. Zwicknagl, C. Geibel, J. F. Landaeta, S. Khim, E. Hassinger, M. Brando","doi":"arxiv-2409.11894","DOIUrl":"https://doi.org/arxiv-2409.11894","url":null,"abstract":"Unconventional superconductivity in heavy-fermion systems appears often near\u0000magnetic quantum critical points (QCPs). This seems to be the case also for\u0000CeRh2As2 (Tc $approx$ 0.31 K). CeRh2As2 shows two superconducting (SC) phases,\u0000SC1 and SC2, for a magnetic field along the c axis of the tetragonal unit cell,\u0000but only the SC1 phase is observed for a field along the basal plane.\u0000Furthermore, another ordered state (phase-I) is observed below T0 $approx$\u00000.48 K whose nature is still unclear: Thermodynamic and magnetic measurements\u0000pointed to a non magnetic multipolar state, but recent $mu$SR and NQR/NMR\u0000experiments have clearly detected antiferromagnetic (AFM) order below T0 .\u0000Also, quasi-two-dimensional AFM fluctuations were observed in NMR and\u0000neutron-scattering experiments above T0. The proximity of a QCP is indicated by\u0000non-Fermi-liquid (NFL) behavior observed above the ordered states in both\u0000specific heat $C(T)/T propto T^{-0.6}$ and resistivity $rho(T) propto\u0000T^{0.5}$. These T-dependencies are not compatible with any generic AFM QCP.\u0000Because of the strong magnetic-field anisotropy of both the SC phase and phase\u0000I, it is possible to study a field-induced SC QCP as well a phase-I QCP by\u0000varying the angle $alpha$ between the field and the c axis. Thus, by examining\u0000the behavior of the electronic specific-heat coefficient C(T)/T across these\u0000QCPs, we can determine which phase is associated with the NFL behavior. Here,\u0000we present low-temperature specific-heat measurements taken in a magnetic field\u0000as high as 21 T applied at several angles $alpha$. We observe that the NFL\u0000behavior does very weakly depend on the field and on the angle $alpha$, a\u0000result that is at odd with that observations in standard magnetic QCPs. This\u0000suggests a nonmagnetic origin of the quantum critical fluctuations.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aitor Calvo-Fernández, María Blanco-Rey, Asier Eiguren
Exploiting symmetries in the numerical renormalization group (NRG) method significantly enhances performance by improving accuracy, increasing computational speed, and optimizing memory efficiency. Published codes focus on continuous rotations and unitary groups, which generally are not applicable to systems with strong crystal-field effects. The PointGroupNRG code implements symmetries related to discrete rotation groups, which are defined by the user in terms of Clebsch-Gordan coefficients, together with particle conservation and spin rotation symmetries. In this paper we present a new version of the code that extends the available finite groups, previously limited to simply reducible point groups, in a way that all point and double groups become accessible. It also includes the full spin-orbital rotation group. Moreover, to improve the code's flexibility for impurities with complex interactions, this new version allows to choose between a standard Anderson Hamiltonian for the impurity or, as another novel feature, an ionic model that requires only the spectrum and the impurity Lehmann amplitudes.
{"title":"Numerical renormalization group calculations for magnetic impurity systems with spin-orbit coupling and crystal-field effects","authors":"Aitor Calvo-Fernández, María Blanco-Rey, Asier Eiguren","doi":"arxiv-2409.12050","DOIUrl":"https://doi.org/arxiv-2409.12050","url":null,"abstract":"Exploiting symmetries in the numerical renormalization group (NRG) method\u0000significantly enhances performance by improving accuracy, increasing\u0000computational speed, and optimizing memory efficiency. Published codes focus on\u0000continuous rotations and unitary groups, which generally are not applicable to\u0000systems with strong crystal-field effects. The PointGroupNRG code implements\u0000symmetries related to discrete rotation groups, which are defined by the user\u0000in terms of Clebsch-Gordan coefficients, together with particle conservation\u0000and spin rotation symmetries. In this paper we present a new version of the\u0000code that extends the available finite groups, previously limited to simply\u0000reducible point groups, in a way that all point and double groups become\u0000accessible. It also includes the full spin-orbital rotation group. Moreover, to\u0000improve the code's flexibility for impurities with complex interactions, this\u0000new version allows to choose between a standard Anderson Hamiltonian for the\u0000impurity or, as another novel feature, an ionic model that requires only the\u0000spectrum and the impurity Lehmann amplitudes.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"212 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vertex corrections from the transversal particle-hole channel, so-called $pi$-tons, are generic in models for strongly correlated electron systems and can lead to a displaced Drude peak (DDP). Here, we derive the analytical expression for these $pi$-tons, and how they affect the optical conductivity as a function of correlation length $xi$, fermion lifetime $tau$, temperature $T$, and coupling strength to spin or charge fluctuations $g$. In particular, for $Trightarrow T_c$, the critical temperature for antiferromagnetic or charge ordering, the dc vertex correction is algebraic $sigma_{VERT}^{dc}propto xi sim (T-T_c)^{-nu}$ in one dimension and logarithmic $sigma_{VERT}^{dc}propto lnxi sim nu ln (T-T_c)$ in two dimensions. Here, $nu$ is the critical exponent for the correlation length. If we have the exponential scaling $xi sim e^{1/T}$ of an ideal two-dimensional system, the DDP becomes more pronounced with increasing $T$ but fades away at low temperatures where only a broadening of the Drude peak remains, as it is observed experimentally. Further, we find the maximum of the DPP to be given by the inverse lifetime: $omega_{DDP} sim 1/tau$. These characteristic dependencies can guide experiments to evidence $pi$-tons in actual materials.
{"title":"Analytical expression for $π$-ton vertex contributions to the optical conductivity","authors":"Juraj Krsnik, Anna Kauch, Karsten Held","doi":"arxiv-2409.11158","DOIUrl":"https://doi.org/arxiv-2409.11158","url":null,"abstract":"Vertex corrections from the transversal particle-hole channel, so-called\u0000$pi$-tons, are generic in models for strongly correlated electron systems and\u0000can lead to a displaced Drude peak (DDP). Here, we derive the analytical\u0000expression for these $pi$-tons, and how they affect the optical conductivity\u0000as a function of correlation length $xi$, fermion lifetime $tau$, temperature\u0000$T$, and coupling strength to spin or charge fluctuations $g$. In particular,\u0000for $Trightarrow T_c$, the critical temperature for antiferromagnetic or\u0000charge ordering, the dc vertex correction is algebraic\u0000$sigma_{VERT}^{dc}propto xi sim (T-T_c)^{-nu}$ in one dimension and\u0000logarithmic $sigma_{VERT}^{dc}propto lnxi sim nu ln (T-T_c)$ in two\u0000dimensions. Here, $nu$ is the critical exponent for the correlation length. If\u0000we have the exponential scaling $xi sim e^{1/T}$ of an ideal two-dimensional\u0000system, the DDP becomes more pronounced with increasing $T$ but fades away at\u0000low temperatures where only a broadening of the Drude peak remains, as it is\u0000observed experimentally. Further, we find the maximum of the DPP to be given by\u0000the inverse lifetime: $omega_{DDP} sim 1/tau$. These characteristic\u0000dependencies can guide experiments to evidence $pi$-tons in actual materials.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. K. Karn, Kapil Kumar, Geet Awana, Kunal Yadav, S. Patnaik, V. P. S. Awana
In this article, we report the synthesis of a single crystalline gray Arsenic (As) via the Bismuth flux method. The as-grown sample has a Rhombohedral structure as the most stable one. Its XRD (X-ray Diffractometry) pattern ensures a single phase of the grown crystal with space group R-3m. The observed sharp XRD peaks on mechanically exfoliated thin flakes ensured the high crystallinity with growth direction along the c-axis. The EDAX (Energy Dispersive X-ray Analysis) endorses the stoichiometric purity of the as-grown As single crystal. To study the vibrational mode, the Raman spectra are recorded, which show peaks at 196.2 cm-1 and 255.74 cm-1, identified as Eg and A1g modes by DFT calculations. The sample is further characterized by electronic and magneto-transport measurements. The resistivity vs temperature measurement illustrates its metallic nature in the temperature range of 2K to 300K. The measured residual resistivity ratio of the sample is 180, which endorses the high quality of the as-synthesized As single crystal. The RH measurement elucidates huge observed magnetoresistance (MR), along with SdH oscillations, which indicate the presence of topological surface states. The topological nature of As is also confirmed by first principle calculations. Not only orbit projected bands show signatures of band inversion but also the Z2invariant value(1,111) calculated by Wilson loop method affirms As to be a strong topological insulator (TI).
在本文中，我们报告了通过铋通量法合成单晶灰色砷（As）的过程。生长后的样品具有最稳定的斜方晶体结构。其 XRD（X 射线衍射测量法）图样显示生长出的晶体为单相，空间群为 R-3m。在机械剥离薄片上观察到的尖锐 XRD 峰确保了沿 c 轴生长方向的高结晶度。能量色散 X 射线分析（EDAX）证实了所生长的砷单晶的化学纯度。为了研究振动模式，记录了拉曼光谱，其中在 196.2 cm-1 和 255.74 cm-1 处出现了峰值，通过 DFT 计算确定为 Eg 和 A1g 模式。通过电子和磁传输测量进一步确定了样品的特性。电阻率与温度的关系测量说明了它在 2K 至 300K 温度范围内的金属性质。测得的样品残余电阻率比为 180，这表明合成的 As 单晶质量很高。剩余电阻率测量结果阐明了所观察到的巨大磁阻（MR）以及 SdHoscillations，这表明存在拓扑表面态。第一原理计算也证实了 As 的拓扑性质。不仅轨道投影带显示了带反转的特征，而且用威尔逊环方法计算出的 Z2 不变值（1,111）也证实了 As 是一种强拓扑绝缘体（TI）。
{"title":"Magneto transport and first principle study of strong topological insulator gray Arsenic","authors":"N. K. Karn, Kapil Kumar, Geet Awana, Kunal Yadav, S. Patnaik, V. P. S. Awana","doi":"arxiv-2409.11016","DOIUrl":"https://doi.org/arxiv-2409.11016","url":null,"abstract":"In this article, we report the synthesis of a single crystalline gray Arsenic\u0000(As) via the Bismuth flux method. The as-grown sample has a Rhombohedral\u0000structure as the most stable one. Its XRD (X-ray Diffractometry) pattern\u0000ensures a single phase of the grown crystal with space group R-3m. The observed\u0000sharp XRD peaks on mechanically exfoliated thin flakes ensured the high\u0000crystallinity with growth direction along the c-axis. The EDAX (Energy\u0000Dispersive X-ray Analysis) endorses the stoichiometric purity of the as-grown\u0000As single crystal. To study the vibrational mode, the Raman spectra are\u0000recorded, which show peaks at 196.2 cm-1 and 255.74 cm-1, identified as Eg and\u0000A1g modes by DFT calculations. The sample is further characterized by\u0000electronic and magneto-transport measurements. The resistivity vs temperature\u0000measurement illustrates its metallic nature in the temperature range of 2K to\u0000300K. The measured residual resistivity ratio of the sample is 180, which\u0000endorses the high quality of the as-synthesized As single crystal. The RH\u0000measurement elucidates huge observed magnetoresistance (MR), along with SdH\u0000oscillations, which indicate the presence of topological surface states. The\u0000topological nature of As is also confirmed by first principle calculations. Not\u0000only orbit projected bands show signatures of band inversion but also the\u0000Z2invariant value(1,111) calculated by Wilson loop method affirms As to be a\u0000strong topological insulator (TI).","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"195 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The magnetic solitons such as chiral solitons, magnetic skyrmions, and magnetic hopfions, exhibiting particlelike nature widely emerge in magnets depending on spatial dimension. As their number directly gives rise to an impact on magnetic properties and electronic properties, it is of great importance to control the number of solitons. However, a systematic study on dynamical processes to control the number of solitons, particularly by adding the desired number of solitons to the ground state exhibiting periodic arrangements of solitons, has been limited thus far. Here, we theoretically perform the systematic analysis for the dynamical control of the number of chiral solitons in monoaxial chiral magnets by effectively utilizing the edge modes whose excitation is localized near the edges. By studying the dynamical process associated with this edge mode in an applied rotating magnetic field by using the Landau-Lifshitz-Gilbert equation, we show that multiple soliton penetrations can take place until the system reaches the nonequilibrium steady state, and the number of infiltrated solitons successively increases with the amplitude of the rotating magnetic field after surpassing the threshold. We also clarify that the threshold amplitude of the rotating magnetic field can be reduced through the static magnetic field. Our results reveal that the desired number of solitons can be added within a certain range by taking advantage of the edge modes that appear without any special processing at the edges of the system. These results contribute to the development of an experimental way to control the number of solitons and are expected to be further applied to a wide range of magnetic solitons, not limited to chiral solitons.
{"title":"Soliton penetration from edges in a monoaxial chiral magnet","authors":"Kotaro Shimizu, Shun Okumura, Yasuyuki Kato, Yukitoshi Motome","doi":"arxiv-2409.10842","DOIUrl":"https://doi.org/arxiv-2409.10842","url":null,"abstract":"The magnetic solitons such as chiral solitons, magnetic skyrmions, and\u0000magnetic hopfions, exhibiting particlelike nature widely emerge in magnets\u0000depending on spatial dimension. As their number directly gives rise to an\u0000impact on magnetic properties and electronic properties, it is of great\u0000importance to control the number of solitons. However, a systematic study on\u0000dynamical processes to control the number of solitons, particularly by adding\u0000the desired number of solitons to the ground state exhibiting periodic\u0000arrangements of solitons, has been limited thus far. Here, we theoretically\u0000perform the systematic analysis for the dynamical control of the number of\u0000chiral solitons in monoaxial chiral magnets by effectively utilizing the edge\u0000modes whose excitation is localized near the edges. By studying the dynamical\u0000process associated with this edge mode in an applied rotating magnetic field by\u0000using the Landau-Lifshitz-Gilbert equation, we show that multiple soliton\u0000penetrations can take place until the system reaches the nonequilibrium steady\u0000state, and the number of infiltrated solitons successively increases with the\u0000amplitude of the rotating magnetic field after surpassing the threshold. We\u0000also clarify that the threshold amplitude of the rotating magnetic field can be\u0000reduced through the static magnetic field. Our results reveal that the desired\u0000number of solitons can be added within a certain range by taking advantage of\u0000the edge modes that appear without any special processing at the edges of the\u0000system. These results contribute to the development of an experimental way to\u0000control the number of solitons and are expected to be further applied to a wide\u0000range of magnetic solitons, not limited to chiral solitons.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shot-noise measures the correlations of fluctuations of current for a voltage applied much larger than the temperature and reveals aspects of correlations in fermions beyond those revealed in the conductivity. Recent measurements of shot-noise in the quantum-critical region of the heavy-fermion compound YbRh$_2$Si$_2$ (YRS) have presented a conceptual challenge to old theory and those devised following the experiments. Since the measured resistivity and the specific heat in YRS follow the predictions of marginal Fermi liquid (MFL) theory, we use it to calculate noise using the method developed by Nagaev. We get fair agreement with the magnitude and temperature dependence in the experiments using parameters from resistivity measurements. To achieve this, we find it necessary that the collisions between fermions by exchanging the MFL fluctuations conserve energy but lose momentum through Umklapp scattering and that the fermions and their fluctuations are locally in mutual equilibrium. %and that the self-energy rides the local chemical potential. At low temperatures, impurity scattering determines the noise and at high temperatures the MFL scattering. We show that the noise for MFL scattering for high T alone is the same as the Johnson-Nyquist noise, which in this case is temperature independent. Therefore the Fano factor crosses over to $0$ at high temperatures independent of the voltage applied.
{"title":"Shot Noise near Quantum-Criticality","authors":"Srinivas Raghu, Chandra M. Varma","doi":"arxiv-2409.10798","DOIUrl":"https://doi.org/arxiv-2409.10798","url":null,"abstract":"Shot-noise measures the correlations of fluctuations of current for a voltage\u0000applied much larger than the temperature and reveals aspects of correlations in\u0000fermions beyond those revealed in the conductivity. Recent measurements of\u0000shot-noise in the quantum-critical region of the heavy-fermion compound\u0000YbRh$_2$Si$_2$ (YRS) have presented a conceptual challenge to old theory and\u0000those devised following the experiments. Since the measured resistivity and the\u0000specific heat in YRS follow the predictions of marginal Fermi liquid (MFL)\u0000theory, we use it to calculate noise using the method developed by Nagaev. We\u0000get fair agreement with the magnitude and temperature dependence in the\u0000experiments using parameters from resistivity measurements. To achieve this, we\u0000find it necessary that the collisions between fermions by exchanging the MFL\u0000fluctuations conserve energy but lose momentum through Umklapp scattering and\u0000that the fermions and their fluctuations are locally in mutual equilibrium.\u0000%and that the self-energy rides the local chemical potential. At low\u0000temperatures, impurity scattering determines the noise and at high temperatures\u0000the MFL scattering. We show that the noise for MFL scattering for high T alone\u0000is the same as the Johnson-Nyquist noise, which in this case is temperature\u0000independent. Therefore the Fano factor crosses over to $0$ at high temperatures\u0000independent of the voltage applied.","PeriodicalId":501171,"journal":{"name":"arXiv - PHYS - Strongly Correlated Electrons","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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