Hidden Charge 2e Boson in Doped Mott Insulators: Field Theory of Mottness

We construct the low energy theory of a doped Mott insulator, such as the high-temperature superconductors, by explicitly integrating over the degrees of freedom far away from the chemical potential. For either hole or electron doping, a charge 2e bosonic field emerges at low energy. The charge 2e boson mediates dynamical spectral weight transfer across the Mott gap and creates a new charge e excitation by binding a hole. The result is a bifurcation of the electron dispersion below the chemical potential as observed recently in angle-resolved photoemission on Pb-doped Bi_2Sr_2CaCu_2O_{8+\delta} (Pb2212).Comment: 4 pages, 2 figures: Correct version to appear in PRL. Revisions include a derivation of the electron operator at low energies which reveals a branching structure seen recently in ARPES on Pb221

Doped Mott insulators are insulators: hole localization in the cuprates

We demonstrate that a Mott insulator lightly doped with holes is still an insulator at low temperature even without disorder. Hole localization obtains because the chemical potential lies in a pseudogap which has a vanishing density of states at zero temperature. The energy scale for the pseudogap is set by the nearest-neighbour singlet-triplet splitting. As this energy scale vanishes if transitions, virtual or otherwise, to the upper Hubbard band are not permitted, the fundamental length scale in the pseudogap regime is the average distance between doubly occupied sites. Consequently, the pseudogap is tied to the non-commutativity of the two limits $U\to\infty$ ($U$ the on-site Coulomb repulsion) and $L\to\infty$ (the system size).Comment: 4 pages, 3 .eps file

Exact Integration of the High Energy Scale in Doped Mott Insulators

We expand on our earlier work (cond-mat/0612130, Phys. Rev. Lett. {\bf 99}, 46404 (2007)) in which we constructed the exact low-energy theory of a doped Mott insulator by explicitly integrating (rather than projecting) out the degrees of freedom far away from the chemical potential. The exact low-energy theory contains degrees of freedom that cannot be obtained from projective schemes. In particular a new charge $\pm 2e$ bosonic field emerges at low energies that is not made out of elemental excitations. Such a field accounts for dynamical spectral weight transfer across the Mott gap. At half-filling, we show that two such excitations emerge which play a crucial role in preserving the Luttinger surface along which the single-particle Green function vanishes. In addition, the interactions with the bosonic fields defeat the artificial local SU(2) symmetry that is present in the Heisenberg model. We also apply this method to the Anderson-U impurity and show that in addition to the Kondo interaction, bosonic degrees of freedom appear as well. Finally, we show that as a result of the bosonic degree of freedom, the electron at low energies is in a linear superposition of two excitations--one arising from the standard projection into the low-energy sector and the other from the binding of a hole and the boson.Comment: Published veriso

Dual Representation: Reviewing the Republic of China’s Last Battle in the UN

[[abstract]]Current studies of Chinese representation in the United Nations assume that the Republic of China's expulsion was inevitable because of Chang Kai-shek's one China principle and Beings role in U.S. foreign policy. This paper provides another perspective on this event by mapping hoe the United States, using a two Chinas strategy, endeavored to secure Taipei's seat and how Chiang Kai-slick faithfully executed this plan.[[incitationindex]]SSCI[[booktype]]電子

Factors influencing consumers’ purchase intention on organic foods via a Theory of Planned Behaviour approach

Even though Asian countries are expected to become a dominant market for organic foods in the coming years, there are few studies which focused on young Asian consumers’ organic food purchase behaviour. This study aims to investigate how attitude, subjective norm, perceived behavioural control, and health concerns influence consumers’ intention to purchase and consume organic foods. A purposive sampling method was adopted for this study and a total of 289 usable questionnaires were collected for empirical testing of the postulated hypotheses using SPSS and structural equation modelling (SEM). The results showed that attitude, subjective norm, perceived behavioural control and health concern positively influenced intention. In addition, subjective norm positively influenced attitude while attitude played a partial mediation effect on the relationship between subjective norm and intention. Lastly, the theoretical and practical implications as well as the limitations of the study are discussed

Impact of familiarity and green image on satisfaction and loyalty among young green hotel's guests - a developing country's perspective

Familiarity and green image influencing travelers’ green hotel patronage have often been overlooked in previous research. The aim of this study was to examine the relationship of the two dimensions of familiarity and the two dimensions of image with the overall image, satisfaction, and loyalty. The theoretical research model used in this study was based on the stimulus–organism–response framework. The research design for this study employed a quantitative approach using a purposive sampling method involving 488 student responses. The tests of the proposed hypotheses were conducted using SPSS and AMOS. The results of the study showed that experiential familiarity and informational familiarity positively influenced cognitive image and affective image, respectively, while cognitive image had a positive influence on the affective image. In addition, cognitive and affective images have a positive influence on the overall image, and the overall image is shown to have a positive impact on satisfaction and loyalty. Finally, satisfaction was found to have a positive influence on loyalty, while satisfaction plays a partial meditation role in the relationship between overall image and loyalty

Influence of Playability on Perceived Game Software Quality: A Comparison Between Chinese and South Korean Gamers

The usability of ISO/IEC 25000 series SQuaRE and other existing software quality models seems unsuitable for unique software products such as game software. This study revealed that playability has a higher predictive capacity than usability for evaluating game software quality using a survey methodology involving 344 Chinese respondents and 142 South Korean respondents. Specifically, dimensions of playability in terms of enjoyable, exciting, fun, interesting, relaxing, novel, creative, convenient, curious, fantastic, stimulating, splendid, effective and attractive positively influenced both Chinese and South Korean game software users’ satisfaction. In addition, results show that there is a significant difference between Chinese and South Koreans in playability dimensions such as exciting, relaxing, novel, creative, convenient, curious, stimulating, splendid and attractive. This study extends the existing knowledge on how playability influenced game software users’ satisfaction and software quality, and limitations were also highlighted

Much Ado about Zeros: The Luttinger Surface and Mottness

We prove that the Mott insulating state is characterized by a divergence of the electron self energy at well-defined values of momenta in the first Brillouin zone. When particle-hole symmetry is present, the divergence obtains at the momenta of the Fermi surface for the corresponding non-interacting system. Such a divergence gives rise to a surface of zeros (the Luttinger surface) of the single-particle Green function and offers a single unifying principle of Mottness from which pseudogap phenomena, spectral weight transfer, and broad spectral features emerge in doped Mott insulators. We also show that only when particle-hole symmetry is present does the volume of the zero surface equal the particle density. We identify that the general breakdown of Luttinger's theorem in a Mott insulator arises from the breakdown of a perturbative expansion for the self energy in the single-particle Green function around the non-interacting limit. A modified version of Luttinger's theorem is derived for special cases.Comment: New version proves explicitly that only when particle-hole symmetry is present does the volume of the surface of zeros equal the particle density thereby generalising recent perturbative argument