Specific heat of 2-d electrons in strong magnetic field

It is shown that the specific heat of an ideal two-dimensional electron gas in strong magnetic field decreases exponentially at low temperatures.     

Specific heat of DyVO4 with applied magnetic field

The specific heat of DyVO₄ was measured as a function of temperature for various applied magnetic fields up to 8T. A quantitative analysis was undertaken using the so-called “compressible Ising model”. The general experimental behaviour was reproduced but discrepancies were observed for the highest fields, presumably due to the importance of short range order interactions which are not satisfactorily taken into account by the model.     

Heavy fermions in a high magnetic field

We give an overview on experimental studies performed in the last 25 years on heavy-fermion systems in a high magnetic field. The properties of field-induced magnetic transitions in heavy-fermion materials close to a quantum antiferromagnetic-to-paramagnetic instability are presented. Effects of a high magnetic field to the Fermi surface, in particular the splitting of spin-up and spin-down bands, are also considered. Finally, we review on recent advances on the study of non-centrosymmetric compounds and ferromagnetic superconductors in a high magnetic field.     

Parallel heat flux from low to high parallel temperature along a magnetic field line

In a long mean-free-path plasma where temperature anisotropy can be sustained, the parallel heat flux has two components with one associated with the parallel thermal energy and the other with the perpendicular thermal energy. In a kinetic simulation with magnetic flux expansion toward an absorbing boundary, the parallel heat flux of the parallel thermal energy is found to flow from a low to high parallel temperature region. This unusual behavior is understood with the help of an analytical calculation of the drift-kinetic model using the same upstream source in the simulation.     

Electron heat transport measured in a stochastic magnetic field

New profile measurements have allowed the electron thermal diffusivity profile to be estimated from power balance in the Madison Symmetric Torus where magnetic islands overlap and field lines are stochastic. The measurements show that (1) the electron energy transport is conductive not convective, (2) the measured thermal diffusivities are in good agreement with numerical simulations of stochastic transport, and (3) transport is greatly reduced near the reversal surface where magnetic diffusion is small.     

Specific heat of nanostructured superconducting tin in magnetic fields

Specific heat of tin nanoparticles, which are embedded in porous glass with average pore size ～7 nm, has been investigated in the low-temperature region in magnetic fields up to 2 T. The temperatures of the transition into the superconducting state in various magnetic fields have been determined for tin nanostructured in porous glass. The H _c -T _c phase diagram has been constructed. The upper critical field has been evaluated and the electronic specific heat coefficient and the Debye temperature have been refined. These results have been discussed within the structural model of tin nanoparticles in porous glass.     

Zero-energy state in graphene in a high magnetic field

The fate of the charge-neutral Dirac point in graphene in a high magnetic field H has been investigated at low temperatures (T approximately 0.3 K). In samples with small gate-voltage offset V0, the resistance R0 at the Dirac point diverges steeply with H, signaling a crossover to a state with a very large R0. The approach to this state is highly unusual. Despite the steep divergence in R0, the profile of R0 vs T in fixed H saturates to a T-independent value below 2 K, consistent with gapless charge-carrying excitations.     

Specific heat of magnetic and semiconductor quasiperiodic structures

We have performed a theoretical study of the specific heat C(T)$C(T)$, as a function of temperature, of magnetic and semiconductor quasiperiodic structures. The quasiperiodic structures considered here are constructed according to the Fibonacci, double-period and Thue–Morse quasiperiodic sequences. On one hand, we assume the magnetic structures composed of ferromagnetic films, each one described by the Heisenberg model. On the other hand, we consider semiconductor structures composed of slabs of AlN and GaN, which are characterized by the dielectric functions _εA(ω)${\epsilon }_A(\omega )$ and _εB(ω)${\epsilon }_B(\omega )$, and have thicknesses _da$d_a$ and _db$d_b$, respectively. Our results illustrate the effects of disorder on the oscillatory behavior of the specific heat in the low temperature regime.     

The excitonic spectrum of germanium in a high magnetic field

In recently reported experiments with uniaxially deformed germanium in a magnetic field [V. B. Timofeev and A. V. Chernenko, JETP Lett. 61, 617 (1995)], it was found that applying a magnetic field of sufficiently high intensity results in the appearance of a new line in the optical spectrum of the excitons. In the present paper a mechanism is proposed which can provide an explanation for this experimentally observed spectral feature. The new spectral line may be attributed to the formation of strongly bound biexcitonic molecules in the quantum state ³Π_u. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 6, 405–409 (25 March 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Intraexcitonic transitions in two-dimensional systems in a high magnetic field

The internal transitions of two-dimensional (2D) excitons in a high magnetic field B exhibit features due to the coupling of the internal and center-of-mass motions. A study is made of these features, and it is shown that for magnetoexcitons with a center-of-mass momentum K ≠0 the energies of the strong transitions decrease with increasing K, and the absorption spectra show weakly resolved transitions, whose total intensity depends strongly on the exciton statistics (distribution function). Pis’ma Zh. éksp. Teor. Fiz. 66, No. 9, 588–593 (10 November 1997)     

Specific heat of EuIn2P2 at high magnetic fields

We have carried out specific heat measurements on EuIn₂P₂ at high magnetic fields perpendicular to the c-axis in the hexagonal crystal structure in order to understand its thermal properties. The temperature dependence of the specific heat exhibits a clear λ-type anomaly due to a magnetic transition at , indicating that the magnetic transition is of second-order. The λ-type anomaly becomes markedly broader with increasing the magnetic field. This remarkable field-dependence is consistent with the results of previous magnetization measurements which suggest that Eu²⁺ magnetic moments align ferromagnetically perpendicular to the c-axis below T_C. In addition, a hump in the specific heat is observed around 7 K, which can be ascribed to the Zeeman splitting of the Eu²⁺ multiplet by internal magnetic fields.     

Specific features of infrared absorption in films materials subjected to a magnetic field

The reflection spectra and magnetorefractive effect (MRE) of metal (Co, CoFe), semiconductor (Si, GaAs), and granular and amorphous Co₃₀Ag₇₀ and Co₅₉Fe₅Ni₁₀Si₁₁B₁₅ films are studied in the IR spectral region at λ=2.5–25 μm. It is found that the IR optical properties of the ferromagnetic metal films can be described with regard to light absorption due to electron transitions in the two spin systems. The MRE is found to occur in both the ferromagnetic (Co, CoFe) and semiconductor (Si, GaAs) films. The amplitude and shape of the MRE are determined for the p and s polarizations of light. It is shown that, to a first approximation, the IR optical properties of the films with giant magnetoresistance can be described by the Drude theory, while the MRE is explained on the basis of a modified Hagen-Rubens relation. Variations in the IR reflection of semiconductor or amorphous metal films in the magnetic field are found to depend on the degree of polarization of localized electron states at the Fermi level.     

Specific heat study of an S = 1/2 alternating Heisenberg chain system: F5PNN in a magnetic field

We have measured the specific heat of an S = 1/2 antiferromagnetic alternating Heisenberg chain pentafulorophenyl nitronyl nitroxide in magnetic fields up to H > H(C2). This compound has a field-induced magnetic ordered (FIMO) phase between H(C1) and H(C2). Characteristic behaviors are observed depending on the magnetic field up to above H(C2) outside of the H-T boundary for the FIMO. The temperature and field dependence of the specific heat are qualitatively in good agreement with the theoretical calculation on an S = 1/2 two-leg ladder [Wang et al., Phys. Rev. Lett. 84, 5399 (2000)]]. This agreement suggests that the observed behaviors are related with the low-energy excitation in the Tomonaga-Luttinger liquid.     

The Wigner crystal in a semimetal film in a high magnetic field

The possibility of existance of a super-crystalline (Wigner) phase in a semimetal or impurity semiconductor film placed in a high magnetic field, is discussed and a comparison is made with a crystal in a three-dimensional specimen.

Such a phase exists in a succession of magnetic field or particle density intervals. The vibrational spectrum depends on magnetic field, while the bind energy is only density-dependent. The mean-square displacement x² of the particles in the lattice sites are also independent on the magnetic field over a wide temperature range.     

Quantum limit in a quasi-one-dimensional conductor in a high tilted magnetic field

Recently, we have suggested Fermi-liquid–non-Fermi-liquid angular crossovers that may exist in quasi-one-dimensional (Q1D) conductors in high tilted magnetic fields (see A. G. Lebed, Phys. Rev. Lett. 115, 157001 (2015)). All calculations in the Letter were done by using the quasiclassical Peierls substitution method, whose applicability in high magnetic fields was questionable. Here, we solve a fully quantum mechanical problem and show that the main qualitative conclusions of the work cited above are correct. In particular, we show that in high magnetic fields, applied along one of the two main crystallographic axis, we have 2D electron spectrum, whereas, for directions of high magnetic fields far from the axes, we have 1D electron spectrum. The latter is known to promote non-Fermi-liquid properties. As a result, we expect the existence of Fermi-liquid–non-Fermi-liquid angular crossovers or phase transitions. Electronic parameters of Q1D conductor (Per)₂Pt(mnt)₂ show that such transitions can appear in feasible high magnetic fields of the order of H ? 20–25 T.