The Third Way of Thermal-Electric Conversion beyond Seebeck and Pyroelectric Effects

Thermal-electric conversion is crucial for smart energy control and harvesting, such as thermal sensing and waste heat recovering. So far, people are aware of only two ways of direct thermal-electric conversion, Seebeck and pyroelectric effects, each with distinct working conditions and limitations. Here, we report the third way of thermal-electric conversion beyond Seebeck and pyroelectric effects. In contrast to Seebeck effect that requires spatial temperature difference, the-third-way converts the time-dependent ambient temperature fluctuation into electricity, similar to the behavior of pyroelectricity. However, the-third-way is also distinct from pyroelectric effect in the sense that it does not require polar materials but applies to general conducting systems. We demonstrate that the-third-way results from the temperature-fluctuation-induced dynamical charge redistribution. It is a consequence of the fundamental nonequilibrium thermodynamics and has a deep connection to the topological phase in quantum mechanics. The findings expand our knowledge and provide new means of thermal-electric energy harvesting.Comment: 4 pages, 3 figure

Asymptotically AdS spacetimes with a timelike Kasner singularity

Exact solutions to Einstein's equations for holographic models are presented and studied. The IR geometry has a timelike cousin of the Kasner singularity, which is the less generic case of the BKL (Belinski-Khalatnikov-Lifshitz) singularity, and the UV is asymptotically AdS. This solution describes a holographic RG flow between them. The solution's appearance is an interpolation between the planar AdS black hole and the AdS soliton. The causality constraint is always satisfied. The entanglement entropy and Wilson loops are discussed. The boundary condition for the current-current correlation function and the Laplacian in the IR is examined. There is no infalling wave in the IR, but instead, there is a normalizable solution in the IR. In a special case, a hyperscaling-violating geometry is obtained after a dimensional reduction.Comment: 22 pages, 3 figures, jheppub; v2: more details added; v3: minor corrections, title changed; original title: "Analytic anisotropic solutions for holography

Effective potential calculation of the MSSM lightest CP-even Higgs boson mass

I summarize results of two-loop effective potential calculations of the lightest CP-even Higgs boson mass in the minimal supersymmetric standard model.Comment: 4 pages, 1 figur

Non-Reciprocal Geometric Wave Diode by Engineering Asymmetric Shapes of Nonlinear Materials

Unidirectional nonreciprocal transport is at the heart of many fundamental problems and applications in both science and technology. Here we study the novel design of wave diode devices by engineering asymmetric shapes of nonlinear materials to realize the function of non-reciprocal wave propagations. We first show analytical results revealing that both nonlinearity and asymmetry are necessary to induce such non-reciprocal (asymmetric) wave propagations. Detailed numerical simulations are further performed for a more realistic geometric wave diode model with typical asymmetric shape, where good non-reciprocal wave diode effect is demonstrated. Finally, we discuss the scalability of geometric wave diodes. The results open a flexible way for designing wave diodes efficiently simply through shape engineering of nonlinear materials, which may find broad implications in controlling energy, mass and information transports.Comment: 4 figure

One-dimensional holographic superconductor from AdS_3/CFT_2 correspondence

We obtain a holographical description of a superconductor by using the d=2 case of the AdS_{d+1}/CFT_d correspondence. The gravity system is a (2+1)-dimensional AdS black hole coupled to a Maxwell field and charged scalar. The dual (1+1)-dimensional superconductor will be strongly correlated. The characteristic exponents for vector perturbations at the boundary degenerate, which implies that d=2 is a critical dimension and the Green's function needs to be regularized. In the normal phase, the current-current correlation function and the conductivity can be analytically solved at zero chemical potential. The dc conductivity can be analytically solved at finite chemical potential. When we add a scalar hair to the black hole, a charged condensate happens at low temperatures. We compare our results with higher-dimensional cases.Comment: 22 pages, 7 figures; v2: minor corrections; v3: published versio

Cohomological Hall algebras, semicanonical bases and Donaldson-Thomas invariants for 22-dimensional Calabi-Yau categories (with an appendix by Ben Davison)

We discuss semicanonical bases from the point of view of Cohomological Hall algebras via the "dimensional reduction" from 3-dimensional Calabi-Yau categories to 2-dimensional ones. Also, we discuss the notion of motivic Donaldson-Thomas invariants (as defined by M. Kontsevich and Y. Soibelman) in the framework of 2-dimensional Calabi-Yau categories. In particular we propose a conjecture which allows one to define Kac polynomials for a 2-dimensional Calabi-Yau category (this is a theorem of S. Mozgovoy in the case of preprojective algebras).Comment: The revised version contains the Appendix written by Ben Davison about the relationship of Kontsevich-Soibelman product with the one of Schiffmann-Vassero

Asymmetric Andreev Reflection Induced Electrical and Thermal Hall-like Effects in Metal/Anisotropic Superconductor Junctions

By investigating the nonequilibrium transport across a metal/superconductor junction in both nonrelativistic and relativistic cases, we reveal that the asymmetric Andreev reflection with anisotropic superconductors is able to induce the electric and thermal Hall-like effect, in the absence of magnetic field. That is, a longitudinal electric voltage or temperature bias can induce transverse electric or thermal currents merely through the asymmetric Andreev reflection, respectively. In particular, a transverse thermoelectric effect, i.e., the Ettingshausen-like effect, is identified, although the conjugate Nernst effect is absent. The direction change of these electric and thermal Hall-like currents is also discussed. The Hall-like effects uncovered here do not require the conventional time-reversal symmetry breaking, but rather originate from the mirror symmetry breaking with respect to the interface normal due to the anisotropic paring symmetry of the superconductor.Comment: 5 pages, 3 figures, published as Phys. Rev. B 89, 064512 (2014). See also http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.06451