A companion problem book to the textbook "Building Physics," offering practical problems that demonstrate solutions common issues in building physics.

The vibrational anomalies of pentacene molecules have been investigated in conjunction with the high-energy excitonic features. Self-trapped excitons have been distinguished from the others.

The n-type organic semiconductor, β-phase single crystalline dichloro naphthalene diimide, Cl2–NDI, is investigated in a broad frequency range via optical spectroscopy. The temperature-dependent ab...

Organic layered charge-transfer salts κ -(BEDT-TTF) 2 X form highly frustrated lattices of molecular dimers in which strong correlations give rise to Mott insulating states situated close to the metal-to-insulator phase boundary. The salts κ -(BEDT-TTF) 2 Cu 2 (CN) 3 and κ -(BEDT-TTF) 2 Ag 2 (CN) 3 have been considered as prime candidates for a quantum spin liquid, while κ -(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl has been suggested as a prototypical charge-order-driven antiferromagnet. In this paper, we summarize and discuss several key results, including some not reported previously, obtained in search to clarify the competition of these two ground states. The origin of anomalous dielectric response found at low temperatures in all three salts is also discussed. We conclude by pointing out the relevant new insights into the role of frustration and random disorder in the suppression of magnetic ordering and formation of the spin liquid state.

The Mott insulator $\beta'$-EtMe$_3$Sb[Pd(dmit)$_2$]$_2$ belongs to a class of charge transfer solids with highly-frustrated triangular lattice of $S=1/2$ molecular dimers and a quantum-spin-liquid ground state. Our experimental and ab initio theoretical studies show the fingerprints of strong correlations and disorder, important role of cation-dimer bonding in charge redistribution, no sign of intra- and inter-dimer dipoles, and the decisive van der Waals contribution to inter-dimer interactions and the ground state structure. The latter consists of quasi-degenerate electronic states related to the different configurations of cation moieties which permit two different equally probable orientations. Upon reducing the temperature, the low-energy excitations slow down, indicating glassy signatures as the cation motion freezes out.

This book provides thorough coverage of the most important building physics phenomena: heat transfer, moisture, sound/acoustics, and illumination. Since the book is primarily aimed at engineers, it ad

The Mott insulator kappa-(BEDT-TTF)(2)Ag-2(CN)(3) forms a highly-frustrated triangular lattice of S = 1/2 dimers with a possible quantum-spin-liquid state. Our experimental and numerical studies reveal the emergence of a slight charge imbalance between crystallographically inequivalent sites, relaxor dielectric response, and hopping dc transport. In a broader perspective we conclude that the universal properties of strongly-correlated charge-transfer salts with spin liquid state are an anion-supported valence band and cyanide-induced quasidegenerate electronic configurations in the relaxed state. The generic low-energy excitations are caused by charged domain walls rather than by fluctuating electric dipoles. They give rise to glassy dynamics characteristic of dimerized Mott insulators, including the sibling compound kappa-(BEDT-TTF)(2)Cu-2(CN)3.

The Mott insulator $\ensuremath{\kappa}\ensuremath{-}{(\mathrm{BEDT}\ensuremath{-}\mathrm{TTF})}_{2}{\mathrm{Ag}}_{2}{(\mathrm{CN})}_{3}$ forms a highly-frustrated triangular lattice of $S=1/2$ dimers with a possible quantum-spin-liquid state. Our experimental and numerical studies reveal the emergence of a slight charge imbalance between crystallographically inequivalent sites, relaxor dielectric response, and hopping dc transport. In a broader perspective we conclude that the universal properties of strongly-correlated charge-transfer salts with spin liquid state are an anion-supported valence band and cyanide-induced quasidegenerate electronic configurations in the relaxed state. The generic low-energy excitations are caused by charged domain walls rather than by fluctuating electric dipoles. They give rise to glassy dynamics characteristic of dimerized Mott insulators, including the sibling compound $\ensuremath{\kappa}\ensuremath{-}(\text{BEDT}\ensuremath{-}\text{TTF}){}_{2}{\mathrm{Cu}}_{2}(\mathrm{CN}){}_{3}$.

Novel forms of the low-temperature phases in the two-dimensional molecular solids with competing interactions between charges, spins and lattice, in particular those featuring anomalous dielectric relaxation, have been the focus of intense activity in recent years. Open issues concern the nature of collective charge excitations as well as their coupling to applied ac and dc electric fields. The charge response is reasonably well understood by now in the charge-ordered phase with the formation of ferroelectric-like domains below the metal-to-insulator phase transition. Conversely, the dielectric response observed in dimer Mott insulator phases with no complete evidence for charge ordering is rather intriguing. We overview our recent results of anisotropic complex conductivity (dc – MHz) in the magnetic phase of κ - ( BEDT - TTF ) 2 Cu [ N ( CN ) 2 ] Cl and in the spin-liquid phase of κ - ( BEDT - TTF ) 2 Cu 2 ( CN ) 3 . We discuss possible explanations for the observed dynamics within current theoretical models and compare them with the well-known fingerprints of the spin density wave response to ac electric fields.

Novel forms of the low-temperature phases in the two-dimensional molecular solids with competing interactions between charges, spins and lattice, in particular those featuring anomalous dielectric relaxation, have been the focus of intense activity in recent years. Open issues concern the nature of collective charge excitations as well as their coupling to applied ac and dc electric fields. The charge response is reasonably well understood by now in the charge-ordered phase with the formation of ferroelectric-like domains below the metal-to-insulator phase transition [1, 2]. Conversely, the dielectric response observed in dimer Mott insulator phases with no charge ordering [3] is rather intriguing [4, 5, 6, 7]. In this presentation we review our in-depth study (dc conductivity, Hall effect and dielectric spectroscopy) of the anisotropic charge response in an unconventional Mott insulator with spin liquid kappa-(BEDT-TTF)2Cu2(CN)3. Variable-range hopping transport within molecular planes in dc limit and an anomalously broad anisotropic dielectric relaxation in audio-frequency range demonstrate the inherent heterogeneity present in nominally pure single crystals of kappa-(BEDT-TTF)2Cu2(CN)3. The relaxation bears fingerprints of relaxor ferroelectricity: a gradual slowing down becomes dominated by tunneling at low temperatures and at the bifurcation temperature anomalous features in dielectric constant, mean relaxation time and spectral broadening are detected. We argue that the observed behavior is due to a strong charge-spin-lattice coupling reflecting the gradual emergence of random potential and domain structure originated in the anion network. [1] T.Ivek et al., Phys.Rev.B83, 165128 (2011). [2] T.Ivek et al., Phys.Rev.B86, 245125 (2012). [3] K.Sedlmeier et al., Phys.Rev.B86, 245103 (2012). [4] M.Abdel-Jawad et al., Phys.Rev.B82, 125119 (2010). [5] S.Iguchi et al., Phys.Rev.B87, 075107 (2013). [6] P.Lunkenheimer et al., Nat. Mater. 11, 755 (2012). [7] S.Tomic et al., J.Phys.: Condens.Matter 25, 436004 (2013). [8] M.Pinteric et al., to be submitted (2014).

We have in detail characterized the anisotropic charge response of the dimer Mott insulator kappa-(BEDT-TTF)(2)Cu-2(CN)(3) by dc conductivity, Hall effect, and dielectric spectroscopy. At room temperature, the Hall coefficient is positive and close to the value expected from stoichiometry; the temperature behavior follows the dc resistivity rho(T). Within the planes the dc conductivity is well described by variable-range hopping in two dimensions; this model, however, fails for the out-of-plane direction. An unusually broad in-plane dielectric relaxation is detected below about 60 K; it slows down much faster than the dc conductivity following an Arrhenius law. At around 17 K, we can identify a pronounced dielectric anomaly concomitantly with anomalous features in the mean relaxation time and spectral broadening. The out-of-plane relaxation, on the other hand, shows a much weaker dielectric anomaly; it closely follows the temperature behavior of the respective dc resistivity. At lower temperatures, the dielectric constant becomes smaller both within and perpendicular to the planes; also, the relaxation levels off. The observed behavior bears features of relaxorlike ferroelectricity. Because heterogeneities impede its long-range development, only a weak-tunneling-like dynamics persists at low temperatures. We suggest that the random potential and domain structure gradually emerge due to the coupling to the anion network.

Belleville washer steel springs are characterized by a long fatigue life, better space utilization, low creep tendency, and high force bearing capacity with a small spring deflection. In the case of thicker springs, a greater force bearing and greater stiffness are obtained, but the deflection of the spring is reduced. In such a case, the fatigue life is reduced and there is a very high probability that a Belleville washer spring may fail in a brittle manner, causing additional damage to machinery. In order to prevent such a fracture of a Belleville washer, an elastomeric filling was used on both free surfaces of the spring. Experimental testing and numerical analyses show that enhanced loading characteristics were obtained when the elastomer filling was increasingly involved in the force bearing process. When the elastomer filling is compressed, the stresses in the Belleville washer steel are reduced, because the majority of the deflection stress is shared by the elastomer instead of the steel.

The electrodynamic response of the organic spin-liquid candidate $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ has been measured in an extremely wide energy range ($10^{-13}$ to 2 eV) as a function of temperature (5 to 300 K). Below the Mott gap, excitations from the un-gapped spinon continuum cause a considerable contribution to the infrared conductivity, as suggested by the U(1) gauge theory. At THz frequencies we can identify a power-law behavior $\sigma(\omega) \propto \omega^{\beta}$ with two distinct exponents $\beta$ that change from 0.9 to 1.3 at low temperatures. The corresponding crossover scales with temperature: $\hbar\omega_c \approx k_B T$. The observed exponents differ by more than a factor of 2 from the theoretically predicted ones. The findings are compared with those obtained on Herbertsmithites.

The Mott insulator κ-(BEDT-TTF)2Cu[N(CN)2]Cl consists of molecular dimers arranged on an anisotropic triangular lattice. At low temperatures a pronounced dielectric anomaly is observed, and eventually a canted antiferromagnetic ground state forms. Optical spectroscopy clearly rules out charge imbalance and the existence of quantum electric dipoles with a dipolar-spin coupling. Here we suggest a novel form of spin–charge coupling where the prominent in-plane dielectric response in κ-(BEDT-TTF)2Cu[N(CN)2]Cl is explained by short-range discommensurations of the antiferromagnetic phase in the temperature range 30 K < T < 50 K, and by relaxation of charged domain walls in the ferromagnetic structure at lower temperatures.