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In this paper, we report the measurements of specific heat of an amorphous Ti9.5Si90.5 alloy located very close to the critical point of the metal-insulator transition. In the presence of a magnetic field, the specific heat is dominated by the Schottky anomaly caused by magnetic moments associated with the dangling bonds in the matrix of amorphous Si. Subtraction of this contribution exposes the behavior of the electronic specific heat coefficient γ . The coefficient is temperature independent above 2 K and is, in order of magnitude, close to the value expected in the absence of electron-electron interactions. In the temperature range 0.4–1.5 K, the coefficient γ shows an anomalous downturn, which can be approximated by the dependence γ (T ) = γ0 ln(T/T0 ), with T0 ≈ 0.2 K. In a companion paper, we found that the Hall coefficient in Ti-Si alloys is affected by the electron-electron interaction up to much higher temperature of 150 K and also varies critically across the metal-insulator transition. We compare our results with theoretical predictions for three models, which can potentially explain the anomalous behavior of the specific heat: generalized nonlinear σ model, Coulomb glass, and many-body localization. 

Abstract We have employed state-of-the-art cross-correlation noise spectroscopy (CCNS) to study carrier dynamics in silicon heterojunction solar cells (SHJ SCs). These cells were composed of a light absorbing n -doped monocrystalline silicon wafer contacted by passivating layers of i - a -Si:H and doped a -Si:H selective contact layers. Using CCNS, we are able to resolve and characterize four separate noise contributions: (1) shot noise with Fano factor close to unity due to holes tunneling through the np-junction, (2) a 1/ f term connected to local potential fluctuations of charges trapped in a-Si:H defects, (3) generation-recombination noise with a time constant between 30 and 50 μs and attributed to recombination of holes at the interface between the ITO and n-a -Si:H window layer, and (4) a low-frequency generation-recombination term observed below 100 K which we assign to thermal emission over the ITO/ ni - a -Si:H interface barrier. These results not only indicate that CCNS is capable of reveling otherwise undetectable relaxation process in SHJ SCs and other multi-layer devices, but also that the technique has a spatial selectivity allowing for the identification of the layer or interface where these processes are taking place. 

The synthesis of a novel family of homoleptic COT-based heterotrimetallic self-assemblies bearing the formula [LnKCa(COT) 3 (THF) 3 ] (Ln( iii ) = Gd, Tb, Dy, Ho, Er, Tm, and Yb) is reported followed by their X-ray crystallographic and magnetic characterization. All crystals conform to the monoclinic P 2 1 / c space group with a slight compression of the unit cell from 3396.4(2) Å 3 to 3373.2(4) Å 3 along the series. All complexes exhibit a triple-decker structure having the Ln( iii ) and K( i ) ions sandwiched by three COT 2− ligands with an end-bound {Ca 2+ (THF) 3 } moiety to form a non-linear (153.5°) arrangement of three different metals. The COT 2− ligands act in a η 8 -mode with respect to all metal centers. A detailed structural comparison of this unique set of heterotrimetallic complexes has revealed consistent trends along the series. From Gd to Yb, the Ln to ring-centroid distance decreases from 1.961(3) Å to 1.827(2) Å. In contrast, the separation of K( i ) and Ca( ii ) ions from the COT-centroid (2.443(3) and 1.914(3) Å, respectively) is not affected by the change of Ln( iii ) ions. The magnetic property investigation of the [LnKCa(COT) 3 (THF) 3 ] series (Ln( iii ) = Gd, Tb, Dy, Ho, Er, and Tm) reveals that the Dy, Er, and Tm complexes display slow relaxation of their magnetization, in other words, single-molecule magnet (SMM) properties. This behaviour is dominated by thermally activated (Orbach-like) and quantum tunneling processes for [DyKCa(COT) 3 (THF) 3 ] in contrast to [ErKCa(COT) 3 (THF) 3 ], in which the thermally activated and Raman processes appear to be relevant. Details of the electronic structures and magnetic properties of these complexes are further clarified with the help of DFT and ab initio theoretical calculations. 

The consequences of four-electron addition to [8]cycloparaphenylene ([8]CPP, 1 ) have been evaluated crystallographically, revealing a significant core deformation. The structural analysis exposes an elliptical distortion observed upon electron transfer, with the deformation parameter (D.P.) increased by 28% in comparison with neutral [8]CPP. The C–C bond length alteration pattern also indicates a quinoidal structural rearrangement upon four-fold reduction. The large internal cavity of [8]CPP 4− allows the encapsulation of two {K + (THF) 2 } cationic moieties with two additional cations bound externally in the solid-state structure of [{K + (THF) 2 } 4 ([8]CPP 4− )]. The experimental structural data have been used as a benchmark for the comprehensive theoretical description of the geometric changes and electronic properties of the highly-charged [8]CPP 4− nanohoop in comparison with its neutral parent. While neutral [8]CPP and the [8]CPP 2− anion clearly show aromatic behavior of all six-membered rings, subsequent addition of two more electrons completely reverses their aromatic character to afford the highly-antiaromatic [8]CPP 4− anion, as evidenced by structural, topological, and magnetic descriptors. The disentanglement of electron transfer from metal binding effects allowed their contributions to the overall core perturbation of the negatively-charged [8]CPP to be revealed. Consequently, the internal coordination of potassium cations is identified as the main driving force for drastic elliptic distortion of the macrocyclic framework upon reduction. 

Cu( i ) and Au( i ) ions, capped with an N-heterocyclic carbene (NHC), react with (TMS) 3 P 7 (TMS = trimethyl-silyl) to afford an η 4 -coordinated anion [NHC Dipp Cu–P 7 (TMS)] − and a neutral trinuclear complex (NHC Dipp Au) 3 P 7 . Protecting the P 7 cage with the TMS groups is instrumental in controlling the course of these reactions.