Temperature and bath size in exact diagonalization dynamical mean field theory

Liebsch, A.; Ishida, Hiroshi

doi:10.1088/0953-8984/24/5/053201

Cited by 109 publications

(138 citation statements)

References 105 publications

Supporting

Mentioning

133

Contrasting

Order By: Relevance

“…We then apply the standard finite-T ED algorithm of Ref. 62, with gradually increasing the temperature from T = 0. In the algorithm, we optimize the bath parameters at each temperature by minimizing the distance function, ).…”

Section: Methodsmentioning

confidence: 99%

Hidden fermionic excitation in the superconductivity of the strongly attractive Hubbard model

et al. 2015

View full text Add to dashboard Cite

We scrutinize the real-frequency structure of the self-energy in the superconducting state of the attractive Hubbard model within the dynamical mean-field theory. Within the strong-coupling superconducting phase which has been understood in terms of the Bose-Einstein condensation in the literature, we find two qualitatively different regions crossing over each other. In one region close to zero temperature, the self-energy depends on the frequency only weakly at low energy. On the other hand, in the region close to the critical temperature, the self-energy shows a pole structure. The latter region becomes more dominant as the interaction becomes stronger. We reveal that the self-energy pole in the latter region is generated by a coupling to a hidden fermionic excitation. The hidden fermion persists in the normal state, where it yields a pseudogap. We compare these properties with those of the repulsive Hubbard model relevant for high-temperature cuprate superconductors, showing that hidden fermions are a key common ingredient in strongly correlated superconductivity.PACS numbers: 67.85. Lm, 71.10.Fd A range of metals show superconductivity below a critical temperature (T c ), at which paired electrons acquire a spatial coherence. In conventional superconductors, the pairing mechanism is well described by the Bardeen-CooperSchrieffer (BCS) theory [1]. However, the BCS theory does not straightforwardly apply when the attractive interaction between electrons is strong. In this case, the electron pairing occurs at a temperature higher than T c and superconductivity arises when the electron pairs (regarded as composite bosons) go through the Bose-Einstein condensation (BEC) at a lower temperature [2]. Such superconductivity in the BEC regime has been explored for ultracold fermionic atom systems [3][4][5]. In fact, tightly-bound pairs [6] and an associated pseudogap behavior [7,8] have been observed for 40 K gas in the strongly-interacting region. A recent experiment also suggested that the superconductivity in FeSe is in the BCS-BEC crossover regime [9]. The preformed pairing has also been proposed in the context of cuprate high-T c superconductors [10,11]. Although it looks unlikely that the preformed pairing solely can explain the whole pseudogap behavior in the cuprates [12][13][14][15], it may be relevant in a region close to T c around the optimal doping [16,17].On the theoretical side, the crossover from BCS to BEC [5,[18][19][20] has been intensively studied with continuous [21][22][23][24][25][26][27] or lattice [28-41] fermion models, both of which give a similar phase diagram. The latter is, however, more tractable with numerical simulations and allows us to employ nonperturbative methods to study this problem. In particular, the dynamical mean-field theory (DMFT) [42], which becomes exact in infinite spatial dimensions, is a suitable tool to study dynamical properties of the lattice models. In fact, the DMFT and its extensions have been extensively applied to the attractive Hubbard model [43][44][45][4...

show abstract

Section: Methodsmentioning

confidence: 99%

Hidden fermionic excitation in the superconductivity of the strongly attractive Hubbard model

et al. 2015

View full text Add to dashboard Cite

show abstract

“…23. Here, we employ the Lanzcos algorithm to solve the local Green's function, and the bath parameters for the finite-size system are obtained by minimizing the following function 30 :…”

Section: Pacs Numbersmentioning

confidence: 99%

Proximity effects in a topological-insulator/Mott-insulator heterostructure

Ueda¹,

Kawakami²,

Sigrist³

2013

Phys. Rev. B

View full text Add to dashboard Cite

We investigate proximity effects in a correlated heterostructure of a two-dimensional Mott insulator (MI) and a topological insulator (TI) by employing inhomogeneous dynamical mean-field theory. We show that the edge state of the TI induces strongly renormalized mid-gap states inside the MI region, which still have a remnant of the helical energy-spectrum. The penetration of low-energy electrons, which is controlled by the interface tunneling V , largely enhances the electron mass inside the MI and also splits a single Dirac-cone at edge sites into the spatially-separated two Dirac-cones in the strong V region. PACS numbers:Remarkable progress has been made in the study of the topological insulator (TI) as a new class of materials characterized by an energy gap in the bulk but gapless edge (surface) states at its boundary 1-3 . In recent experiments, the observation of such TIs is reported for HgTe/CdTe quantum wells 2,4 and some bismuth compounds (such as Bi 2 Se 3 and Bi 1−x Sb x ) 5-8 , corresponding to two-and three-dimensional TIs, respectively. Edge states of TIs are protected by non-trivial topological properties of the electronic bulk spectrum, thereby being robust against small perturbations conserving timereversal symmetry, such as non-magnetic impurities 9 . Hence, as long as the bulk gap exists, the low-energy physics of the TI is dominated by the edge states.Heterostructures involving the TIs are currently the subject of intensive studies as they might have applications in future spintronics devices. They also provide a versatile platform for searching exotic interface phenomena, such as Majonara bound states 10,11 and anomalous magnetoresistance 12 . In particular, we would like to explore the interface physics which emerges in a heterostructure composed of a TI and strongly correlated materials, since the previous studies of TI have mainly focused on heterostructures involving non-interacting electrons.Regarding heterostructures with electron correlations, recent years have seen tremendous advances in producing high-quality interfaces composed of various materials such as band-insulator/Mott-insulator (BI/MI) or different types of band insulators. Unusual properties have been discovered at these interfaces, such as strongly confined metallic phases 13 , magnetism 14 , and superconductivity 15 to name a few. The occurrence of a metallic interface through electronic rearrangement is one of the intriguing features of the BI/MI heterostructures 16-21 . Naturally we may ask how the situation is modified when the band insulator is replaced by a topological insulator (TI). The interface metallic state should be influenced by the presence of topological edge states and the interplay between such edge states and the strong electron correlation can give rise to novel physical properties.In this study, we analyze the electronic properties at a two-dimensional heterostructure consisting of a paramagnetic Mott insulator (MI) and a TI, by using a rather simple microscopic model for both insulators of TI/MI hete...

show abstract

“…The presence of a spin liquid phase has been supported by other works [3][4][5] using quantum cluster methods [6], such as the Variational Cluster Approximation (VCA) [7,8], the Cluster Dynamical Impurity Approximation (CDIA) [8,9] and Cluster Dynamical Mean Field Theory (CDMFT) [10][11][12][13]. Quantum cluster methods have been used extensively in the last decade to refine our understanding of the Mott-Hubbard transition and of competing orders (magnetism, superconductivity) in strongly correlated materials.…”

Section: Introductionmentioning

confidence: 98%

Absence of Spin Liquid in Nonfrustrated Correlated Systems

Hassan

Sénéchal

2013

Phys. Rev. Lett.

View full text Add to dashboard Cite

The question of the existence of a spin liquid state in the half-filled Hubbard model on the honeycomb (aka graphene) lattice is revisited. The Variational Cluster Approximation (VCA), the Cluster Dynamical Mean Field Theory (CDMFT) and the Cluster Dynamical Impurity Approximation (CDIA) are applied to various cluster systems. Assuming that the spin liquid phase coincides with the Mott insulating phase in this non-frustrated system, we find that the Mott transition is pre-empted by a magnetic transition occuring at a lower value of the interaction U , and therefore the spin liquid phase does not occur. This conclusion is obtained using clusters with two bath orbitals connected to each boundary cluster site. We argue that using a single bath orbital per boundary site is insufficient and leads to the erroneous conclusion that the system is gapped for all nonzero values of U .

show abstract

Temperature and bath size in exact diagonalization dynamical mean field theory

Cited by 109 publications

References 105 publications

Hidden fermionic excitation in the superconductivity of the strongly attractive Hubbard model

Hidden fermionic excitation in the superconductivity of the strongly attractive Hubbard model

Proximity effects in a topological-insulator/Mott-insulator heterostructure

Absence of Spin Liquid in Nonfrustrated Correlated Systems

Contact Info

Product

Resources

About