The Elusive Bose Metal

Phillips, Philip; Dalidovich, Denis

doi:10.1126/science.1088253

Cited by 160 publications

(192 citation statements)

References 55 publications

(105 reference statements)

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“…Both high mobility 2DEGs and highly disordered amorphous ultrathin metal films exhibit large positive magneto-resistance for in-plane magnetic fields at low temperatures [2]. This is consistent with theoretical arguments that attribute the existence of a metallic ground state to strong antiferromagnetic or singlet correlations between electrons [3] in the appropriate range of densities. When these correlations are quenched by the Zeeman energy in a magnetic field, the metallic state is lost, and the resulting insulator accounts for the large positive magnetoresistance.…”

supporting

confidence: 73%

Ambipolar Gate Effect and Low Temperature Magnetoresistance of UltrathinLa0.8Ca0.2M
Eblen‐Zayas
¹
,
Bhattacharya
²
,
Staley
³

et al. 2005
Phys. Rev. Lett.

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Ultrathin La0.8Ca0.2MnO3 films have been measured in a field-effect geometry. The electric field due to the gate produces a large ambipolar decrease in resistance at low temperatures. This is attributed to the development of a pseudogap in the density of states and the coupling of localized charge to strain. The gate effect and magnetoresitance are interpreted in a consistent framework. The implications for the low temperature behavior of a manganite film in the two dimensional limit are discussed.Ultrathin films of manganites present a unique opportunity for studying the low temperature properties of a half-metallic fully spin polarized electron gas in the twodimensional limit, with tunable disorder. In the past decade, there has been a resurgence of interest in the possible ground states of highly correlated two-dimensional electron gases (2DEGs) [1], especially regarding the existence of a metallic state at low temperatures. Both high mobility 2DEGs and highly disordered amorphous ultrathin metal films exhibit large positive magneto-resistance for in-plane magnetic fields at low temperatures [2]. This is consistent with theoretical arguments that attribute the existence of a metallic ground state to strong antiferromagnetic or singlet correlations between electrons [3] in the appropriate range of densities. When these correlations are quenched by the Zeeman energy in a magnetic field, the metallic state is lost, and the resulting insulator accounts for the large positive magnetoresistance. In the manganites, due to strong Hund's coupling between the core Mn spins and the conduction electrons, a fully spin-polarized electron gas is obtained at low temperatures in the ferromagnetic state. This does not allow for singlet correlations, and should result in an insulating ground state in the two-dimensional limit, even in the presence of very weak disorder. Furthermore, the strong cross-couplings between strain, charge and spin that exist in these systems make for unique features in their response to external perturbations. Localized electrons at the Mn 3+ sites cause lattice distortions via the JahnTeller effect, and as a result, strain fields develop within the lattice. When electrons are delocalized, either by better alignment of spins by an external magnetic field (double-exchange mechanism) or via changing the local density of charge (electrostatic gating), the strain is relieved and the resulting disorder potential is reduced.In this letter we investigate the low temperature properties of ultrathin films of La 0.8 Ca 0.2 MnO 3 (LCMO) to gate and magnetic fields. This composition of LCMO is close to the phase boundary between a ferromagnetic metal (FM) at higher Ca doping and a ferromagnetic charge ordered insulator (F-COI) at lower doping. Bulk single crystals of similar composition are believed to exist in a mixed phase with coexisting regions of insulating and metallic properties [4], with the behavior at low temperatures arising from percolation of metallic regions in the material. The samples are typicall...

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supporting

confidence: 73%

Ambipolar Gate Effect and Low Temperature Magnetoresistance of UltrathinLa0.8Ca0.2M
Eblen‐Zayas
¹
,
Bhattacharya
²
,
Staley
³

et al. 2005
Phys. Rev. Lett.

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“…We therefore consider the B = 1.5 T trace to represent a transitional state in the path the system takes from being a superconductor to an insulator. It is a matter of some debate whether this transitional state will develop into a full superconductor in the T = 0 limit [6,15,16,17]. Experimental realization of this limit is not possible.…”

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confidence: 99%

Experimental Evidence for a Collective Insulating State in Two-Dimensional Superconductors

et al. 2005

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We present the results of an experimental study of the current-voltage characteristics in strong magnetic field (B) of disordered, superconducting, thin-films of amorphous Indium-Oxide. As the B strength is increased superconductivity degrades, until a critical field (B c ) where the system is forced into an insulating state. We show that the differential conductance measured in the insulating phase vanishes abruptly below a well-defined temperature, resulting in a clear threshold for conduction. Our results indicate that a new collective state emerges in two-dimensional superconductors at high B.

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“…There, evidence was found supporting the existence of a spin liquid surrounded by two magnetically ordered states, namely, an antiferromagnetic (collinear) state at lower (higher) J 2 /J 1 . The spin-liquid phase was suggested to be gapless and characterized by a distinctive parameter dependent feature in the momentum distribution n(k), similar to a Bose surface, thus suggesting the presence of an exotic Bose metal [20,24,[26][27][28][29][30][31].…”

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confidence: 99%

Nature of the phases in the frustratedXYmodel on the honeycomb lattice

et al. 2013

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We study the phase diagram of the frustrated XY model on the honeycomb lattice by using accurate correlated wave functions and variational Monte Carlo simulations. Our results suggest that a spin-liquid state is energetically favorable in the region of intermediate frustration, intervening between two magnetically ordered phases. The latter ones are represented by classically ordered states supplemented with a long-range Jastrow factor, which includes relevant correlations and dramatically improves the description provided by the purely classical solution of the model. The construction of the spin-liquid state is based on a decomposition of the underlying bosonic particles in terms of spin-1/2 fermions (partons), with a Gutzwiller projection enforcing no single occupancy, as well as a long-range Jastrow factor.PACS numbers: 75.10. Kt, 67.85.Jk, 21.60.Fw, 75.10.Jm A quantum spin liquid is an exotic state in which strong quantum fluctuations (usually generated by frustration) preclude ordering or freezing, even at zero temperature [1]. Despite intensive theoretical and experimental research, finding quantum spin liquids in materials and in realistic spin models continues to be a challenge. A remarkable example where the existence of such a state has been inferred is the spin-1/2 kagome-lattice Heisenberg antiferromagnet, which has been extensively studied both theoretically and experimentally [1][2][3], even though the precise nature of the spin-liquid state (gapped vs gapless) is still under debate [3][4][5][6]. Another model that has recently received considerable attention for its potential to realize spin-liquid states is the spin-1/2 Heisenberg model on the honeycomb lattice, with nearest-neighbor (NN) J 1 and next-to-nearest neighbor (NNN) J 2 exchange interactions [7][8][9][10][11][12][13][14][15][16]. This is in part motivated by its close relation to the Hubbard model, for which the possibility of having a spin-liquid ground state has been under close scrutiny [17][18][19].A closely related spin model with a rich phase diagram and the promise to support a gapless spin liquid phase is the J 1 − J 2 spin-1/2 XY model on the honeycomb lattice [20,21], which is the main subject of this Rapid Communication. Its Hamiltonian can be written aswhere S α i is the αth component of the spin-1/2 operator at site i. This model can be thought of as a Haldane-Bose-Hubbard model [20,[22][23][24], i.e., the Haldane model [25] on the honeycomb lattice with NN hopping J 1 and complex NNN hopping |J 2 |e ıφ , where spinless fermions are replaced by hard-core bosons and φ = 0. Hard-core boson creation and annihilation operators can then be mapped onto spin operators ((1). The total number of bosons (N ) is related to the total magnetization in the spin language, since n i = S z i + 1/2. Here, we focus on the half-filled case, where N equals one half the number of sites (V ).This model was studied in Ref.[20] by means of exact diagonalization on small clusters. There, evidence was found supporting the existence of a spin liq...

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The Elusive Bose Metal

Cited by 160 publications

References 55 publications

Ambipolar Gate Effect and Low Temperature Magnetoresistance of UltrathinLa0.8Ca0.2M
Eblen‐Zayas
¹
,
Bhattacharya
²
,
Staley
³

et al. 2005
Phys. Rev. Lett.

Ambipolar Gate Effect and Low Temperature Magnetoresistance of UltrathinLa0.8Ca0.2M
Eblen‐Zayas
¹
,
Bhattacharya
²
,
Staley
³

et al. 2005
Phys. Rev. Lett.

Experimental Evidence for a Collective Insulating State in Two-Dimensional Superconductors

Nature of the phases in the frustratedXYmodel on the honeycomb lattice

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The Elusive Bose Metal

Cited by 160 publications

References 55 publications

Ambipolar Gate Effect and Low Temperature Magnetoresistance of UltrathinLa0.8Ca0.2MEblen‐Zayas1, Bhattacharya2, Staley3 et al. 2005Phys. Rev. Lett.

Ambipolar Gate Effect and Low Temperature Magnetoresistance of UltrathinLa0.8Ca0.2MEblen‐Zayas1, Bhattacharya2, Staley3 et al. 2005Phys. Rev. Lett.

Experimental Evidence for a Collective Insulating State in Two-Dimensional Superconductors

Nature of the phases in the frustratedXYmodel on the honeycomb lattice

Contact Info

Product

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Ambipolar Gate Effect and Low Temperature Magnetoresistance of UltrathinLa0.8Ca0.2M
Eblen‐Zayas
¹
,
Bhattacharya
²
,
Staley
³

et al. 2005
Phys. Rev. Lett.

Ambipolar Gate Effect and Low Temperature Magnetoresistance of UltrathinLa0.8Ca0.2M
Eblen‐Zayas
¹
,
Bhattacharya
²
,
Staley
³

et al. 2005
Phys. Rev. Lett.