Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userObservation of dynamic charge stripes in Tm0.19Yb0.81B12 at the metal-insulator transition
104
0
0.0
(
0
)
Added by
Nikolay Sluchanko E
Publication date
2018
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
Higher accuracy low temperature charge transport measurements in combination with precise X-ray diffraction experiment have allowed detecting the symmetry lowering in the single domain Tm0.19Yb0.81B12 crystals of the family of dodecaborides with metal-insulator transition. Basing on the fine structure analysis we discover formation of dynamic charge stripes within the semiconducting matrix of Tm0.19Yb0.81B12. The charge dynamics in these metallic nano-size conducting channels is characterized by broad-band optical spectroscopy that allowed estimating the frequency (~2.4 10^11 Hz) of quantum motion of the charge carriers. It is suggested that caused by cooperative Jahn-Teller effect in the boron sub-lattice, the large amplitude rattling modes of the Tm and Yb ions are responsible for modulation of the conduction band along [110] direction through the variation of 5d-2p hybridization of electron states.
rate research
Read More
The insulator-to-metal transition continues to be a challenging subject, especially when electronic correlations are strong. In layered compounds, such as La2-xSrxNiO4 and La2-xBaxCuO4, the doped charge carriers can segregate into periodically-spaced charge stripes separating narrow domains of antiferromagnetic order. Although there have been theoretical proposals of dynamically fluctuating stripes, direct spectroscopic evidence of charge-stripe fluctuations has been lacking. Here we report the detection of critical lattice fluctuations, driven by charge-stripe correlations, in La2-xSrxNiO4 using inelastic neutron scattering. This scattering is detected at large momentum transfers where the magnetic form factor suppresses the spin fluctuation signal. The lattice fluctuations associated with the dynamic charge stripes are narrow in q and broad in energy. They are strongest near the charge stripe melting temperature. Our results open the way towards the quantitative theory of dynamic stripes and for directly detecting dynamical charge stripes in other strongly-correlated systems, including high-temperature superconductors such as La2-xSrxCuO4.
The model strongly correlated electron system Ho0.8Lu0.2B12 which demonstrates a cooperative Jahn-Teller instability of the boron sub-lattice in combination with rattling modes of Ho(Lu) ions, dynamic charge stripes and unusual antiferromagnetic (AF) ground state has been studied in detail at low temperatures by magnetoresistance, magnetization and heat capacity measurements. Based on received results it turns out that the angular H-fi-T magnetic phase diagrams of this non-equilibrium AF metal can be reconstructed in the form of a Maltese cross. The dramatic AF ground state symmetry lowering of this dodecaboride with fcc crystal structure can be attributed to the redistribution of conduction electrons which leave the RKKY oscillations of the electron spin density to participate in the dynamic charge stripes providing with extraordinary changes in the indirect exchange interaction between magnetic moments of Ho3+ ions and resulting in the emergence of a number of various magnetic phases. It is also shown that the two main contributions to magnetoresistance in the complex AF phase, the (i) positive linear on magnetic field and the (ii) negative quadratic component can be separated and analyzed quantitatively, correspondingly, in terms of charge carrier scattering on spin density wave (5d) component of the magnetic structure and on local 4f-5d spin fluctuations of holmium sites.
Precise angle-resolved magnetoresistance and magnetization measurements have revealed (i) strong charge transport and magnetic anisotropy and (ii) emergence of a huge number of magnetic phases in the ground state of TmB12 antiferromagnetic metal with fcc crystal structure and dynamic charge stripes. By analyzing the angular H-fi magnetic phase diagrams reconstructed from experimental angle-resolved magnetoresistance and magnetization data we argue that the symmetry lowering is a consequence of suppression of the indirect Ruderman- Kittel-Kasuya-Yosida (RKKY) exchange along 110 directions between nearest neighboring magnetic moments of Tm3+ ions and subsequent redistribution of conduction electrons to quantum fluctuations of the electron density (stripes). Magnetoresistance components are discussed in terms of charge scattering on the spin density wave, itinerant ferromagnetic nano-domains and on-site Tm3+ spin fluctuations.
5d transition metal oxides offer new opportunities to test our understanding of the interplay of correlation effects and spin-orbit interactions in materials in the absence of a single dominant interaction. The subtle balance between solid-state interactions can result in new mechanisms that minimize the interaction energy, and in material properties of potential use for applications. We focus here on the 5d transition metal oxide NaOsO3, a strong candidate for the realization of a magnetically driven transition from a metallic to an insulating state exploiting the so-called Slater mechanism. Experimental results are derived from non-resonant and resonant x-ray single crystal diffraction at the Os L-edges. A change in the crystallographic symmetry does not accompany the metal-insulator transition in the Slater mechanism and, indeed, we find no evidence of such a change in NaOsO3. An equally important experimental observation is the emergence of the (300) Bragg peak in the resonant condition with the onset of magnetic order. The intensity of this space-group forbidden Bragg peak continuously increases with decreasing temperature in line with the square of intensity observed for an allowed magnetic Bragg peak. Our main experimental results, the absence of crystal symmetry breaking and the emergence of a space-group forbidden Bragg peak with developing magnetic order, support the use of the Slater mechanism to interpret the metal-insulator transition in NaOsO3. We successfully describe our experimental results with simulations of the electronic structure and, also, with an atomic model based on the established symmetry of the crystal and magnetic structure.
It has been proposed that an extended version of the Hubbard model which potentially hosts rich possibilities of correlated physics may be well simulated by the transition metal dichalcogenide (TMD) moir{e} heterostructures. Motivated by recent reports of continuous metal insulator transition (MIT) at half filling, as well as correlated insulators at various fractional fillings in TMD moir{e} heterostructures, we propose a theory for the potentially continuous MIT with fractionalized electric charges. The charge fractionalization at the MIT will lead to experimental observable effects, such as a large universal resistivity jump and interaction driven bad metal at the MIT, as well as special scaling of the quasi-particle weight with the tuning parameter. These predictions are different from previously proposed theory for continuous MIT.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
