scholarly journals Universal size-dependent nonlinear charge transport in single crystals of the Mott insulator Ca2RuO4

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
G. Avallone ◽  
R. Fermin ◽  
K. Lahabi ◽  
V. Granata ◽  
R. Fittipaldi ◽  
...  
Keyword(s):  
Sample Size ◽  
Single Crystals ◽  
Current Density ◽  
Equilibrium Phase ◽  
Mott Insulator ◽  
Metallic Phase ◽  
Tuning Parameter ◽  
Strongly Correlated Electron ◽  
Simultaneous Application ◽  
Correlated Electron

AbstractThe surprisingly low current density required for inducing the insulator to metal transition has made Ca2RuO4 an attractive candidate material for developing Mott-based electronics devices. The mechanism driving the resistive switching, however, remains a controversial topic in the field of strongly correlated electron systems. Here we probe an uncovered region of phase space by studying high-purity Ca2RuO4 single crystals, using the sample size as principal tuning parameter. Upon reducing the crystal size, we find a four orders of magnitude increase in the current density required for driving Ca2RuO4 out of the insulating state into a non-equilibrium phase which is the precursor to the fully metallic phase. By integrating a microscopic platinum thermometer and performing thermal simulations, we gain insight into the local temperature during simultaneous application of current and establish that the size dependence is not a result of Joule heating. The findings suggest an inhomogeneous current distribution in the nominally homogeneous crystal. Our study calls for a reexamination of the interplay between sample size, charge current, and temperature in driving Ca2RuO4 towards the Mott insulator to metal transition.

scholarly journals The Ancient Romans’ Route to Charge Density Waves in Cuprates

2019 ◽  
Vol 4 (2) ◽  
pp. 60 ◽  
Author(s):  
Sergio Caprara
Keyword(s):  
Charge Density ◽  
Density Wave ◽  
Metallic Phase ◽  
Charge Density Waves ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Density Waves ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron

An account is given of the main steps that led the research group in Rome, to which the author belongs, to the formulation of the charge-density-wave scenario for high- T c superconducting cuprates. The early finding of the generic tendency of strongly correlated electron systems with short range interactions to undergo electron phase separation was subsequently contrasted with the homogenizing effect of the long-range Coulomb interaction. The two effects can find a compromise in the formation of incommensurate charge density waves. These charge density waves are inherently dynamical and are overdamped as a consequence of the possibility to decay in electron-hole pairs, yet tend to maintain a (quantum) critical character, which is mirrored in their marked momentum and frequency dependence and in their strong variation with temperature and doping. These dynamical incommensurate charge density waves act as mediators of pairing lading to high- T c superconductivity, and provide the scattering mechanism that produces the observed violation of the Fermi-liquid paradigm in the metallic phase.

scholarly journals Indication of Strongly Correlated Electron Transport and Mott Insulator in Disordered Multilayer Ferritin Structures (DMFS)

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4527
Author(s):  
Christopher Rourk ◽  
Yunbo Huang ◽  
Minjing Chen ◽  
Cai Shen
Keyword(s):  
Quantum Dots ◽  
Electron Transport ◽  
Transition Metal ◽  
Strongly Correlated Electrons ◽  
Mott Insulator ◽  
Material Behavior ◽  
Correlated Electrons ◽  
Strongly Correlated ◽  
Strongly Correlated Electron ◽  
Correlated Electron

Electron tunneling in ferritin and between ferritin cores (a transition metal (iron) oxide storage protein) in disordered arrays has been extensively documented, but the electrical behavior of those structures in circuits with more than two electrodes has not been studied. Tests of devices using a layer-by-layer deposition process for forming multilayer arrays of ferritin that have been previously reported indicate that strongly correlated electron transport is occurring, consistent with models of electron transport in quantum dots. Strongly correlated electrons–electrons that engage in strong electron-electron interactions have been observed in transition metal oxides and quantum dots and can create unusual material behavior that is difficult to model, such as switching between a low resistance metal state and a high resistance Mott insulator state. This paper reports the results of the effect of various degrees of structural homogeneity on the electrical characteristics of these ferritin arrays. These results demonstrate for the first time that these structures can provide a switching function associated with the circuit that they are contained within, consistent with the observed behavior of strongly correlated electrons and Mott insulators.

scholarly journals Quantum billiards with correlated electrons confined in triangular transition metal dichalcogenide monolayer nanostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jan Ravnik ◽  
Yevhenii Vaskivskyi ◽  
Jaka Vodeb ◽  
Polona Aupič ◽  
Igor Vaskivskyi ◽  
...  
Keyword(s):  
Transition Metal ◽  
Quantum Interference ◽  
Equilibrium Phase ◽  
Atomic Scale ◽  
Localized States ◽  
Correlated Electrons ◽  
Transition Metal Dichalcogenide ◽  
Strongly Correlated Electron ◽  
Correlated Electron ◽  
Unit Cells

AbstractForcing systems through fast non-equilibrium phase transitions offers the opportunity to study new states of quantum matter that self-assemble in their wake. Here we study the quantum interference effects of correlated electrons confined in monolayer quantum nanostructures, created by femtosecond laser-induced quench through a first-order polytype structural transition in a layered transition-metal dichalcogenide material. Scanning tunnelling microscopy of the electrons confined within equilateral triangles, whose dimensions are a few crystal unit cells on the side, reveals that the trajectories are strongly modified from free-electron states both by electronic correlations and confinement. Comparison of experiments with theoretical predictions of strongly correlated electron behaviour reveals that the confining geometry destabilizes the Wigner/Mott crystal ground state, resulting in mixed itinerant and correlation-localized states intertwined on a length scale of 1 nm. The work opens the path toward understanding the quantum transport of electrons confined in atomic-scale monolayer structures based on correlated-electron-materials.

scholarly journals Propagation of shear stress in strongly interacting metallic Fermi liquids enhances transmission of terahertz radiation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
D. Valentinis ◽  
J. Zaanen ◽  
D. van der Marel
Keyword(s):  
Shear Stress ◽  
Terahertz Radiation ◽  
Fermi Liquid ◽  
Zero Sound ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
Collisionless Regime ◽  
Propagating Shear ◽  
Mass Enhancement

AbstractA highlight of Fermi-liquid phenomenology, as explored in neutral $$^3$$ 3 He, is the observation that in the collisionless regime shear stress propagates as if one is dealing with the transverse phonon of a solid. The existence of this “transverse zero sound” requires that the quasiparticle mass enhancement exceeds a critical value. Could such a propagating shear stress also exist in strongly correlated electron systems? Despite some noticeable differences with the neutral case in the Galilean continuum, we arrive at the verdict that transverse zero sound should be generic for mass enhancement higher than 3. We present an experimental setup that should be exquisitely sensitive in this regard: the transmission of terahertz radiation through a thin slab of heavy-fermion material will be strongly enhanced at low temperature and accompanied by giant oscillations, which reflect the interference between light itself and the “material photon” being the actual manifestation of transverse zero sound in the charged Fermi liquid.

scholarly journals Electrical transport properties and Kondo effect in La1−xPrxNiO3−δ thin films

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Van Hien-Hoang ◽  
Nak-Kwan Chung ◽  
Heon-Jung Kim
Keyword(s):  
Thin Films ◽  
Electrical Transport ◽  
Kondo Effect ◽  
Magnetic Moments ◽  
Structural Disorder ◽  
Strongly Correlated ◽  
Electrical Transport Properties ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron

AbstractThe Kondo effect has been a topic of intense study because of its significant contribution to the development of theories and understanding of strongly correlated electron systems. In this work, we show that the Kondo effect is at work in La1−xPrxNiO3−δ (0 ≤ x ≤ 0.6) thin films. At low temperatures, the local magnetic moments of the 3d eg electrons in Ni2+, which form because of oxygen vacancies, interact strongly with itinerant electrons, giving rise to an upturn in resistivity with x ≥ 0.2. Observation of negative magnetoresistance, described by the Khosla and Fisher model, further supports the Kondo picture. This case represents a rare example of the Kondo effect, where Ni2+ acts as an impurity in the background of Ni3+. We suggest that when Ni2+ does not participate in the regular lattice, it provides the local magnetic moments needed to scatter the conduction electrons in the Kondo effect. These results offer insights into emergent transport behaviors in metallic nickelates with mixed Ni3+ and Ni2+ ions, as well as structural disorder.

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