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4.0
Jun 7, 2022
06/22
by
T Clay
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21
Feb 13, 2020
02/20
by
T Clay
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eye 21
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Oct 8, 2019
10/19
by
T Clay
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eye 57
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0
0.0
Jul 21, 2022
07/22
by
T Clay
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eye 0
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2
2.0
Jul 13, 2022
07/22
by
T Clay
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eye 2
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0
0.0
Jul 21, 2022
07/22
by
T Clay
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Oct 9, 2019
10/19
by
T Clay
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eye 15
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2
2.0
Jun 7, 2022
06/22
by
T Clay
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eye 2
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15
Oct 17, 2019
10/19
by
B T Clay
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eye 15
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Jul 19, 2013
07/13
by
Albert T. Clay
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Jul 20, 2013
07/13
by
R. T. Clay; S. Mazumdar
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Strong co-operative interactions occur between four different broken symmetries involving charge-ordering and bond distortions in the quarter-filled correlated zigzag electron ladder. The ground state is singlet, with spin gap several times larger than in the spin-Peierls state of the one-dimensional quarter-filled chain with the same parameters. We propose the quarter-filled zigzag electron ladder model for several different organic charge-transfer solids with coupled pairs of...
Source: http://arxiv.org/abs/cond-mat/0406525v2
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4.0
Jun 30, 2018
06/18
by
S. Mazumdar; R. T. Clay
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Attempts to explain correlated-electron superconductivity have largely focused on the proximity of the superconducting state to antiferromagnetism. Yet, there exist many correlated-electron systems that exhibit insulator-superconducting transitions where the insulating state exhibits spatial broken symmetry different from antiferromagnetism. Here we focus on a subset of such compounds which are seemingly very different in which specific chemical stoichiometries play a distinct role, and small...
Topics: Superconductivity, Strongly Correlated Electrons, Condensed Matter
Source: http://arxiv.org/abs/1403.2262
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Sep 18, 2013
09/13
by
R. T. Clay; S. Mazumdar
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Comment on Phys. Rev. Lett. 86, 2086 (2001)
Source: http://arxiv.org/abs/cond-mat/0105595v1
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Sep 21, 2013
09/13
by
R. T. Clay; S. Mazumdar
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eye 60
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Strong commensurate antiferromagnetism proximate to superconductivity is found in some members of the kappa-(ET) family, while a spin gap (SG) is found in the theta-(ET). Both kappa- and theta-(ET) materials have frustrated triangular lattice structures. We show from calculations of spin-spin correlations within the effective half-filled band triangular lattice proposed for the kappa-ET, as well as for the real lattice, that long range AFM order is not obtained as a consequence of this...
Source: http://arxiv.org/abs/cond-mat/0407334v2
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Sep 20, 2013
09/13
by
S. Mazumdar; R. T. Clay
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eye 58
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We demonstrate a robust frustration-driven charge-order to superconductivity transition in the half-filled negative-U extended Hubbard model. Superconductivity extends over a broad region of the parameter space. We argue that the model provides the correct insight to understanding unconventional superconductivity in the organic charge-transfer solids and other quarter-filled systems.
Source: http://arxiv.org/abs/0802.1011v1
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Sep 17, 2013
09/13
by
R. T. Clay; S. Mazumdar
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We show that the proposed zig--zag charge--ordering model for alpha'--NaV2O5 is incompatible with a single transition that induces both charge--ordering and spin gap. We introduce a two--band model for alpha'--NaV2O5 within which the simultaneous charge--spin order transition is driven principally by electron-phonon interactions. The spin gap is due to the formation of local dimers, thus explaining the weak magnetic effect on this transition.
Source: http://arxiv.org/abs/cond-mat/0305479v1
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Sep 18, 2013
09/13
by
R. T. Clay; R. P. Hardikar
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We present a detailed numerical study of the Hubbard-Holstein model in one dimension at half filling, including full finite-frequency quantum phonons. At half filling, the effects of the electron-phonon and electron-electron interactions compete, with the Holstein phonon coupling acting as an effective negative Hubbard onsite interaction U that promotes on-site electron pairs and a Peierls charge-density wave state. Most previous work on this model has assumed that only Peierls or U>0 Mott...
Source: http://arxiv.org/abs/cond-mat/0505184v2
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Sep 20, 2013
09/13
by
R. P. Hardikar; R. T. Clay
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The Hubbard-Holstein model is one of the simplest to incorporate both electron-electron and electron-phonon interactions. In one dimension at half filling the Holstein electron-phonon coupling promotes onsite pairs of electrons and a Peierls charge density wave while the Hubbard onsite Coulomb repulsion U promotes antiferromagnetic correlations and a Mott insulating state. Recent numerical studies have found a possible third intermediate phase between Peierls and Mott states. From direct...
Source: http://arxiv.org/abs/cond-mat/0612273v2
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15
Oct 30, 2020
10/20
by
T Clay; G H E Hopkins
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eye 15
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Jul 24, 2013
07/13
by
S. Mazumdar; R. T. Clay; H. Li
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eye 44
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We show that superconductivity is absent within the 1/2-filled band triangular lattice repulsive Hubbard model that has been proposed for organic charge-transfer solids. We posit that organic superconductivity is rather reached from a Bond-Charge Density Wave that either constitutes the insulating state proximate to superconductivity, or is extremely close in energy to the antiferromagnetic state, and replaces the latter under pressure. The Bond-Charge Density Wave can be described within an...
Source: http://arxiv.org/abs/0807.4523v1
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Sep 22, 2013
09/13
by
H. Li; R. T. Clay; S. Mazumdar
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The competition between antiferromagnetic and spin-singlet ground states within quantum spin models and the 1/2-filled band Hubbard model has received intense scrutiny. Here we demonstrate a frustration-induced transition from N\'{e}el antiferromagnetism to spin-singlet in the interacting 1/4-filled band on an anisotropic triangular lattice. While the antiferromagnetic state has equal charge densities 0.5 on all sites, the spin-singlet state is a paired-electron crystal, with pairs of...
Source: http://arxiv.org/abs/0908.4109v2
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Sep 18, 2013
09/13
by
S. Dayal; R. T. Clay; S. Mazumdar
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eye 54
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We present many-body calculations of superconducting pair-pair correlations in the ground state of the half-filled band Hubbard model on large anisotropic triangular lattices. Our calculations cover nearly the complete range of anisotropies between the square and isotropic triangular lattice limits. We find that the superconducting pair-pair correlations decrease monotonically with increasing onsite Hubbard interaction U for inter-pair distances greater than nearest neighbor. For the large...
Source: http://arxiv.org/abs/1201.5139v2
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47
Sep 23, 2013
09/13
by
N. Gomes; R. T. Clay; S. Mazumdar
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A frustrated, effective 1/2-filled band Hubbard-Heisenberg model has been proposed to describe the strongly dimerized charge-transfer solid families kappa-(ET)_2X and Z[Pd(dmit)_2]_2. In addition to unconventional superconductivity these materials also exhibit antiferromagnetism, candidate spin-liquid phases, and in the case of Z=EtMe_3P, a so-called valence-bond solid phase. We show that neither superconductivity nor the valence-bond solid phase occurs within the Hubbard-Heisenberg model,...
Source: http://arxiv.org/abs/1305.0843v1
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Sep 19, 2013
09/13
by
R. T. Clay; H. Li; S. Mazumdar
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eye 47
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We describe the Paired Electron Crystal (PEC) which occurs in the interacting frustrated two-dimensional 1/4-filled band. The PEC is a charge-ordered state with nearest-neighbor spin singlets separated by pairs of vacant sites, and can be thought of as a bipolaron density wave. The PEC has been experimentally observed in the insulating state proximate to superconductivity in the organic charge-transfer solids. Increased frustration drives a PEC-to-superconductor transition in these systems.
Source: http://arxiv.org/abs/0910.2728v1
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Sep 23, 2013
09/13
by
H. Li; R. T. Clay; S. Mazumdar
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A natural explanation for the carrier concentration-dependent electronic behavior in the layered cobaltates emerges within correlated-electron Hamiltonians with finite on-site and significant nearest neighbor hole-hole Coulomb repulsions. The nearest neighbor repulsion decreases hole double-occupancy below hole density 1/3, but increases the same at higher hole densities. Our conclusion is valid for both single-band and three-band extended Hubbard Hamiltonians, and sheds light on...
Source: http://arxiv.org/abs/1012.3118v2
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Sep 18, 2013
09/13
by
R. T. Clay; S. Mazumdar; H. Li
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eye 55
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We suggest that superconductivity (SC) in the organic charge transfer solids (CTS) is reached from a Bond-Charge Density Wave (BCDW). We discuss an effective model for the BCDW to SC transition, an attractive U extended Hubbard Hamiltonian with repulsive nearest neighbor interaction V. We discuss experimental consequences of the theory for different classes of CTS superconductors as well as related inorganic materials.
Source: http://arxiv.org/abs/0809.1583v1
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Sep 22, 2013
09/13
by
R. T. Clay; H. Li; S. Mazumdar
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eye 41
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We report exact calculations of magnetic and superconducting pair-pair correlations for the half-filled band Hubbard model on an anisotropic triangular lattice. Our results for the magnetic phases are similar to those obtained with other techniques. The superconducting pair-pair correlations at distances beyond nearest neighbor decrease monotonically with increasing Hubbard interaction U for all anisotropy, indicating the absence of frustration-driven superconductivity within the model.
Source: http://arxiv.org/abs/0805.0590v1
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Sep 19, 2013
09/13
by
R. T. Clay; S. Mazumdar; D. K. Campbell
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eye 58
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Previous work has demonstrated the existence of soliton defect states with charges +/- e/2 in the limits of zero and of infinite on-site Coulomb interactions in the one-dimensional (1D) quarter-filled band. For large but finite on-site Coulomb interaction, the low temperature 2k_F bond distortion that occurs within the 4k_F bond-distorted phase is accompanied by charge-ordering on the sites. We show that a ``re-integerization'' of the defect charge occurs in this bond-charge density wave (BCDW)...
Source: http://arxiv.org/abs/cond-mat/0010272v1
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133
Jul 20, 2013
07/13
by
S. Mazumdar; R. T. Clay; D. K. Campbell
texts
eye 133
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Two-dimensional (2D) strongly correlated electron systems underlie many of the most important phenomena in contemporary condensed matter physics, including the Quantum Hall Effect (QHE), ``high T_c'' superconductivity, and possible exotic conducting states in silicon MOSFETs. We demonstrate the existence of yet another exotic ground state in strongly correlated, 2D electronic materials: a novel, insulating bond-order/charge density wave state (BCDW) in the commensurate 1/4-filled band that...
Source: http://arxiv.org/abs/cond-mat/9910164v1
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71
Sep 18, 2013
09/13
by
R. T. Clay; R. P. Hardikar; S. Mazumdar
texts
eye 71
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It is known that within the interacting electron model Hamiltonian for the one-dimensional 1/4-filled band, the singlet ground state is a Wigner crystal only if the nearest neighbor electron-electron repulsion is larger than a critical value. We show that this critical nearest neighbor Coulomb interaction is different for each spin subspace, with the critical value decreasing with increasing spin. As a consequence, with the lowering of temperature, there can occur a transition from a Wigner...
Source: http://arxiv.org/abs/0704.1656v2
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58
Sep 21, 2013
09/13
by
R. T. Clay; S. Mazumdar; D. K. Campbell
texts
eye 58
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We investigate theoretically charge ordered states on the anisotropic triangular lattice characteristic of the theta-(BEDT-TTF)_2 X materials. Using exact diagonalization studies, we establish that the charge order (CO) pattern corresponds to a ``horizontal'' stripe structure, with ...1100... CO along the two directions with larger electron hopping (p-directions), and ...1010... CO along the third direction (c-direction). The CO is accompanied by co-operative bond dimerizations along all three...
Source: http://arxiv.org/abs/cond-mat/0203266v1
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5.0
Jun 30, 2018
06/18
by
A. B. Ward; R. T. Clay; S. Mazumdar
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eye 5
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Yoshimi et al. [arXiv:1110.3573] have attempted to explain the pressure(P)-dependent behavior of Fabre salts which exhibit charge order (CO), antiferromagnetic (AFM), and spin-Peierls (SP) phases. Experiments find two AFM phases, AFM1 at large P and AFM2 at small P. Yoshimi et al. suggest that there also exist two distinct zero-temperature SP phases, SP1 and SP2. Here we point out that the occurrence of two distinct SP phases contradicts experiments, and is found because of unrealistic model...
Topics: Strongly Correlated Electrons, Condensed Matter
Source: http://arxiv.org/abs/1403.0120
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37
Sep 19, 2013
09/13
by
S. Mazumdar; R. T. Clay; D. K. Campbell
texts
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Charge and spin-orderings in the 1/4-filled organic CT solids are of strong interest, especially in view of their possible relations to organic superconductivity. We show that the charge order (CO) in both 1D and 2D CT solids is of the ...1100... type, in contradiction to mean field prediction of >...1010... CO. We present detailed computations for metal-insulator and magnetic insulator-insulator transitions in the theta-ET materials. Complete agreement with experiments in several theta...
Source: http://arxiv.org/abs/cond-mat/0209410v1
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68
Sep 22, 2013
09/13
by
S. Mazumdar; R. T. Clay; D. K. Campbell
texts
eye 68
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We report two surprising results regarding the nature of the spatial broken symmetries in the two-dimensional (2D), quarter-filled band with strong electron-electron interactions. First, in direct contradiction to the predictions of one-electron theory, we find a coexisting ``bond-order and charge density wave'' (BCDW) insulating ground state in the 2D rectangular lattice for all anisotropies, including the isotropic limit. Second, we find that the BCDW further coexists with a spin-density wave...
Source: http://arxiv.org/abs/cond-mat/0003200v2
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80
Sep 23, 2013
09/13
by
R. T. Clay; S. Dayal; H. Li; S. Mazumdar
texts
eye 80
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The occurrence of antiferromagnetism in kappa-(ET)_2X can be understood within an effective 1/2-filled band with dimers of ET molecules containing one hole each. We argue that while this effective model can describe the presence of antiferromagnetism, a complete description for these materials requires the correct carrier density of one-half per molecule. For dimerized and strongly frustrated 1/4-filled lattices we show that a singlet-paired state coexisting with charge ordering occurs that we...
Source: http://arxiv.org/abs/1111.5666v1
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52
Sep 18, 2013
09/13
by
S. Dayal; R. T. Clay; H. Li; S. Mazumdar
texts
eye 52
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We present a study of the effects of simultaneous charge- and spin-frustration on the two-dimensional strongly correlated quarter-filled band on an anisotropic triangular lattice. The broken-symmetry states that dominate in the weakly frustrated region near the rectangular lattice limit are the well known antiferromagnetic state with in-phase lattice dimerization along one direction, and the Wigner crystal state with the checkerboard charge order. For moderate to strong frustration, however,...
Source: http://arxiv.org/abs/1102.1731v1
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3.0
Jun 29, 2018
06/18
by
R. T. Clay; A. B. Ward; N. Gomes; S. Mazumdar
texts
eye 3
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Metal-insulator transition accompanied by charge-ordering has been widely investigated in quasi-one-dimensional conductors, including in particular organic charge-transfer solids. Among such materials the 1/4-filled band charge-transfer solids are of strong interest, because of the commensurate nature of the charge-ordering in these systems. The period-four charge-order pattern ...1100... here is accompanied by two distinct bond distortion patterns, giving rise to bond-charge-density waves...
Topics: Condensed Matter, Strongly Correlated Electrons
Source: http://arxiv.org/abs/1608.07599
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67
Sep 22, 2013
09/13
by
S. Mazumdar; S. Ramasesha; R. T. Clay; D. K. Campbell
texts
eye 67
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Recent experiments indicate that the spin-density waves (SDWs) in (TMTTF)_2Br, (TMTSF)_2PF_6 and alpha-(BEDT-TTF)_2MHg(SCN)_4 are highly unconventional and coexist with charge-density waves (CDWs). We present a microscopic theory of this unusual CDW-SDW coexistence. A complete understanding requires the explicit inclusion of strong Coulomb interactions, lattice discreteness, the anisotropic two-dimensional nature of the lattice, and the correct bandfilling within the starting Hamiltonian.
Source: http://arxiv.org/abs/cond-mat/9807308v1
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47
Sep 21, 2013
09/13
by
R. T. Clay; J. P. Song; S. Dayal; S. Mazumdar
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eye 47
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We consider the simplest example of lattice frustration in the 1/4-filled band, a one-dimensional chain with next-nearest neighbor interactions. For this zigzag ladder with electron-electron as well as electron-phonon interactions we present numerical results for ground state as well as thermodynamic properties. In this system the ground state bond distortion pattern is independent of electron-electron interaction strength. The spin gap in the ground state of the zigzag ladder increases with...
Source: http://arxiv.org/abs/1108.4169v2
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3.0
Jun 29, 2018
06/18
by
W. Wasanthi De Silva; N. Gomes; S. Mazumdar; R. T. Clay
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eye 3
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We present the results of precise correlated-electron calculations on the monomer lattices of the organic charge-transfer solids $\kappa$-(BEDT-TTF)$_2$X for 32 and 64 molecular sites. Our calculations are for band parameters corresponding to X = Cu[N(CN)$_2$]Cl and Cu$_2$(CN)$_3$, which are semiconducting antiferromagnetic and quantum spin liquid, respectively, at ambient pressure. We have performed our calculations for variable electron densities $\rho$ per BEDT-TTF molecule, with $\rho$...
Topics: Superconductivity, Condensed Matter, Strongly Correlated Electrons
Source: http://arxiv.org/abs/1602.08480
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73
Sep 17, 2013
09/13
by
R. T. Clay; H. Li; S. Sarkar; S. Mazumdar; T. Saha-Dasgupta
texts
eye 73
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It has been suggested that the metal-insulator transitions in a number of spinel materials with partially-filled t_2g d-orbitals can be explained as orbitally-driven Peierls instabilities. Motivated by these suggestions, we examine theoretically the possibility of formation of such orbitally-driven states within a simplified theoretical model, a two-dimensional checkerboard lattice with two directional metal orbitals per atomic site. We include orbital ordering and inter-atom electron-phonon...
Source: http://arxiv.org/abs/1003.2367v2
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53
Sep 24, 2013
09/13
by
M. Ashida; Y. Taguchi; Y. Tokura; R. T. Clay; S. Mazumdar; Yu. P. Svirko; M. Kuwata-Gonokami
texts
eye 53
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Femtosecond pump-probe measurements find pronounced dimensionality dependence of the optical nonlinearity in cuprates. Although the coherent two-photon absorption (TPA) and linear absorption bands nearly overlap in both quasi-one and two-dimensional (1D and 2D) cuprates, the TPA coefficient is one order of magnitude smaller in 2D than in 1D. Furthermore, picosecond recovery of optical transparency is observed in 1D cuprates, while the recovery in 2D involves relaxation channels with a time...
Source: http://arxiv.org/abs/cond-mat/0103233v1
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44
Sep 17, 2013
09/13
by
J. L. Musfeldt; S. Brown; S. Mazumdar; R. T. Clay; M. Mas-Torent; C. Rovira; J. C. Dias; R. T. Henriques; M. Almeida
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eye 44
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We measured the variable temperature infrared response of the spin ladder candidate (DTTTF)2Cu(mnt)2 in order to distinguish between two competing ladder models, rectangular versus zigzag, proposed for this family of materials. The distortion along the stack direction below 235 K is consistent with a doubling along b through the metal-insulator transition. While this would agree with either of the ladder models, the concomitant transverse distortion rules out the rectangular ladder model and...
Source: http://arxiv.org/abs/0711.1558v1
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322
Apr 18, 2019
04/19
by
ALBERT T. CLAY, Ph.D
texts
eye 322
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Title: Amarru the home of the Northern Semites . Author: ALBERT T. CLAY, Ph.D . Publication Date: 1909.
Topics: Amarru, Semites
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47
Apr 2, 2021
04/21
by
Hilprecht, H. V., and A. T. Clay
texts
eye 47
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None
Topics: Electronic Tools and Ancient Near East Archives (ETANA), Babylonian expedition of the University of...
