Non-Fermi Liquid behavior at the Orbital Ordering Quantum Critical Point in the Two-Orbital Model

The critical behavior of a two-orbital model with degenerate $d_{xz}$ and $d_{yz}$ orbitals is investigated by multidimensional bosonization. We find that the corresponding bosonic theory has an overdamped collective mode with dynamical exponent $z=3$, which appears to be a general feature of a two-orbital model and becomes the dominant fluctuation in the vicinity of the orbital-ordering quantum critical point. Since the very existence of this $z=3$ overdamped collective mode induces non-Fermi liquid behavior near the quantum critical point, we conclude that a two-orbital model generally has a sizable area in the phase diagram showing non-Fermi liquid behavior. Furthermore, we show that the bosonic theory resembles the continuous model near the d-wave Pomeranchuk instability, suggesting that orbital order in a two-orbital model is identical to nematic order in a continuous model. Our results can be applied to systems with degenerate $d_{xz}$ and $d_{yz}$ orbitals such as iron-based superconductors and bilayer strontium ruthenates Sr$_3$Ru$_2$O$_7$.Comment: 5 pages, 2 figure

A study of travel behavior, travel preferences, and subjective well-being of older persons in Hong Kong

Demographic ageing of the population is now well established in Hong Kong and, as elsewhere, is raising increasing concerns about the basic needs and the well-being of older persons. Older individuals vary considerably and may try to enhance their well-being in different ways by a range of leisure activities. The gradually improving financial and physical status suggests travel as a potential leisure activity which might enhance individual well-being and quality of life of older persons. Previous research about travel has mainly involved marketing and sociological perspectives. The market research to date for investigating customer values of tourism and typologies of tourists in sociological studies largely ignored the subjective, dynamic, and intangible components of consumption experience. These components, however, are important for understanding travel needs of older persons. The aims of the current study were therefore to identify the characteristics of travel behavior and the main factors that contribute to a pleasurable trip of older persons to investigate travel preferences and travel needs of older persons. The concept of subjective well-being (SWB) which focuses on the positive affect, negative affect, and life satisfaction was found to be useful for understanding the conditions under which travel is desirable to older persons. Two focus groups were conducted to provide insights for the initial design of an in-depth questionnaire survey of 25 older persons age over 60 or above. Inclusion criteria were that respondents would perceive themselves to be able to travel financially and physically before they completed individual face-to-face interviews. By purposive sampling, respondents were selected from urban areas in Hong Kong from sources including social organizations, the researcher’s personal networks, a church, a university, parks, a shopping mall, and public areas in government buildings. After collecting and analyzing the data referring to principles of grounded theory, four patterns of travel behavior and outcome of travel regarding to individual well-being were found. Six aspects of travel preferences and nine factors which contribute to a pleasurable trip were identified. Travel needs of older persons were further investigated and implications for providing travel services for older persons to enhance their well-being were discussed