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1.
A band mechanism for transport in single-crystal strontium titanate (STO) is used as a basis for estimating the parameters
characterizing the localization and redistribution of space charge in STO for T<100 K. A comparison of the experimental and calculated temperature dependences of the charge carrier concentration yield
an estimate for the location of the Fermi level in STO at T=4.2 K with E
F-E
v∼10 meV. The phenomena at metal/STO and YBCO/STO contacts are discussed.
Fiz. Tverd. Tela (St. Petersburg) 39, 349–352 (February 1997) 相似文献
2.
The static conductivity σ(E) and photoconductivity (PC) at radiation frequencies ħω=10 and 15 meV in Si doped with shallow impurities (density N=1016−6×1016 cm−3, ionization energy ε1≃45 meV) with compensation K=10−4−10−5 in electric fields E=10–250 V/cm are measured at liquid-helium temperatures T. Special measures are taken to prevent the high-frequency part of the background radiation (ħω>16 meV) from striking the
sample. It is found that the conductivity σ(E) is due to carrier motion along the D
− band, which is filled with carriers under the influence of the field E. In fields E<E
q
(E
q
≃100–200 V/cm) the carrier motion consists of hops along localized D
− states in a 10–15 meV energy band below the bottom of the free band (energy ε=ε1); for E>E
q
carriers drift along localized D
− states with energy ε∞ε1−10 meV. An explanation is proposed for the threshold behavior of the field dependence of the photo-and static conductivities.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 232–236 (25 August 1997) 相似文献
3.
The dynamics of formation of the macroscopically occupied polariton mode at the bottom of the polariton band E
LP(k = 0) and its spin polarization under the quasiresonant pulse excitation of excitons (E = E
X
) with large values of quasi-momentum have been studied in planar GaAs microcavities. It has been found that the growth in
the depth E
X
− E
LP(k = 0) of the polariton band leads to the change in the formation mechanism for the k = 0 condensate state from the direct parametric decay of the photoexcited mode (due to the polariton-polariton interaction)
to the dynamic condensation of polaritons, which results from the multiple scattering of polaritons by both phonons and polaritons.
At the same time, in microcavities with E
X
− E
LP(k = 0) > 3.5 meV, the direct decay of the photoexcited mode does not disappear, becoming an efficient mechanism for the filling
of the states located at the k-space ring, corresponding to the energies E
LP(k) ≈ E
X
− 2.6 meV. 相似文献
4.
S. V. Demishev A. V. Semeno N. E. Sluchanko N. A. Samarin J. Singleton A. Ardavan S. J. Blundell W. Hayes S. Kunii 《JETP Letters》1996,64(10):760-766
In undoped pure single crystals of the mixed valence compound SmB6 anomalous ESR absorption is observed in the frequency range v=40–120 GHz at temperatures of 1.8–4.2 K. The ESR for the case of the coherent ground state consists of two components corresponding
to g-factors g
1=1.907±0.003 and g
2=1.890±0.003. The amplitude of both ESR lines strongly depends on temperature in the temperature range studied: the amplitude
of the first line with g=g
1 increases and the amplitude of the second line decreases with temperature. A model based on consideration of intrinsic defects
in the SmB6 crystalline lattice, with a densit ∼1015−1016 cm−3, is suggested as an explanation for the anomalous ESR-behavior. In the frequency range v>70 GHz at T=4.2 K, in addition to the main ESR lines, a new magnetic resonance with a hysteretic field dependence is discovered.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 707–712 (25 November 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
5.
Results are presented from the first stage of studies on the passage of an electron beam with energy 100–500 eV in a magnetic
field of 300–700 Oe through the curvilinear solenoid of the KRéL unit, the latter being a prototype of the closing segment
of the Drakon stellarator system, in the plasma-beam discharge regime. The ion density at the end of the curvilinear part
of the chamber, n
i
≈8×108–1010 cm−3, the electron temperature T
e
≈4–15 eV, and the positions at which the beam hits the target for different distances from it to the electron source are determined
experimentally. The motion of the electron beam is computationally modeled with allowance for the space charge created by
the beam and the secondary plasma. From a comparison of the experimentally measured trajectories and trajectories calculated
for different values of the space charge, we have obtained an estimate for the unneutralized ion density of the order of 5×107 cm−3.
Zh. Tekh. Fiz. 69, 22–26 (February 1999) 相似文献
6.
E. V. Nefedova P. A. Alekseev E. S. Klement’ev V. N. Lazukov I. P. Sadikov M. N. Khlopkin M. B. Tsetlin E. S. Konovalova Yu. B. Paderno 《Journal of Experimental and Theoretical Physics》1999,88(3):565-573
The magnetic susceptibility, electrical resistance, specific heat, and thermal expansion coefficient of SmB6, Sm0.8B6, and Sm1–x
LaxB6 (x=0.1 and 0.2) are measured in the temperature range T=4–300 K. The dispersion curves of the acoustic phonon branches in lanthanum-doped samples are studied. A combined analysis
of the results confirms the existence of an activation gap in the electron density of states in both nonstoichiometric and
lanthanum-doped compounds. The anomalies in the electronic component of the thermal expansion coefficient are associated to
a considerable degree with the temperature variation of the valence and, like the magnetic susceptibility, reflect features
of the f-electron excitation spectrum. It is found that lanthanum doping does not lead to significant changes in the anomalies in
the phonon spectrum of SmB6. It is established that the homogeneous intermediate-valent state of the samarium ion is fairly stable and is maintained
when the perfection of the Sm sublattice is violated.
Zh. éksp. Teor. Fiz. 115, 1024–1038 (March 1999) 相似文献
7.
A. Yu. Yakubovskii S. V. Gudenko N. V. Anshukova A. I. Golovashkin L. I. Ivanova A. P. Rusakov 《Journal of Experimental and Theoretical Physics》1999,88(4):732-737
Electron paramagnetic resonance (EPR) spectra of samples of the systems Ba1−x
KxBiO3 and BaPbyBi1−y
O3 are investigated over wide ranges of composition and temperature. Two main lines in the EPR spectrum with factors g
1≈2.1 and g
2≈4.2 are found for all compositions. It is shown that the observed EPR line with g
2≈4.2 is due to oxygen ions. This probably indicates the presence of oxygen ions with different effective charges, i.e., the
existence of charge density waves in the oxygen-ion sublattice in addition to charge density waves in the bismuth sublattice.
Zh. éksp. Teor. Fiz. 115, 1326–1336 (April 1999) 相似文献
8.
The energy E of the system as a function of the gauge phase Φ is calculated by exact diagonalization in a two-dimensional Cu4O8 cluster and by the slave-boson method for large systems. It is shown that motion of carriers with charge 2e, i.e., Cooper pairs, is observed for certain values of the parameters in the Hamiltonian. This motion is identified from
the onset of a characteristic maximum of E(Φ) at Φ≈Φ0/2, where Φ0 is the flux quantum. The phase diagram is constructed and the range of values of the model parameters where the effect is
observed is determined.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 78–82 (25 January 1996) 相似文献
9.
I. V. Gasenkova M. K. Zhitinskaya S. A. Nemov T. E. Svechnikova 《Physics of the Solid State》1999,41(11):1805-1808
X-ray photoelectron spectroscopy is used to investigate the redistribution of the density of electronic states in the valence
band, and of the binding energies and chemical shifts of core levels in bismuth telluride caused by introduction of impurity
tin atoms. A substantial increase in the density of electronic states below the valence-band top at energies μ≈15–30 meV has been revealed. This feature in the energy spectrum accounts for the unusual behavior of the kinetic coefficients
in p-Bi2Te3:Sn crystals.
Fiz. Tverd. Tela (St. Petersburg) 41, 1969–1972 (November 1999) 相似文献
10.
V. I. Kadushkin 《Russian Physics Journal》2006,49(3):268-275
The volume (3D), quasi-two-dimentional (Q2D), and two-dimentional (2D) oscillations of degenerated electrons of the Shubnikov-de
Haase reluctance reveal common properties. The region of quantum oscillations is bounded (in the magnetic field) from below
by the weak field condition (ωcτt≤1) and from above by the quantum limit condition (ξF≥ħωc/2). The monotonic oscillation component is saturated for the occupied main conduction Em-subband and excitation Ep-subband of dimensional quantization for the Q2D and 2D electron systems in strong magnetic fields. The reluctance of the
Q2D system in the quantum limit changes according to a law ∼B
α with α ≈ 2.6–2.8. The oscillation amplitude is described by an exponential dependence on the magnetic field strength and
temperature, similarly to the 3D case. This is caused by the identity of physical conditions and the topology of resonant
escape of the Landau levels out of the Fermi surface.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 33–39, March, 2006. 相似文献
11.
The fundamental properties of the AlN and GaN compounds with a wurtzite structure under external hydrostatic pressure, uniaxial
mechanical stress σ⊥ along the hexagonal axis, and biaxial mechanical stress σ⊥ in the basal plane of the unit cell have been considered in terms of first-principles calculations in the frame-work of the
density functional theory. The pressures of the phase transitions from the structures of wurtzite and zinc blende to the structure
of rock salt have been obtained. The behavior of the structural parameters, interband transitions, and positions of the charge
neutrality level has been investigated. The calculated pressure coefficients of the band gap are as follows: ∂E
g
/∂p = 40.9 meV/GPa, −∂E
g
/∂σ
| = −4.2 meV/GPa, and −∂E
g
/∂σ
⊥ = 45.2 meV/GPa for AlN and ∂E
g
/∂p = 33.0 meV/GPa, −∂E
g
/∂σ
| = 23.6 meV/GPa, and −∂E
g
/∂σ
⊥ = 9.6 meV/GPa for GaN. The pressure coefficients of the charge neutrality level in almost all cases are substantially smaller
than the corresponding values obtained for the band gap E
g
. 相似文献
12.
F. T. Reis L. F. Santos R. F. Bianchi H. N. Cunha D. Mencaraglia R. M. Faria 《Applied Physics A: Materials Science & Processing》2009,96(4):909-914
In this paper, a detailed study of the capacitance spectra obtained from Au/doped-polyaniline/Al structures in the frequency
domain (0.05 Hz–10 MHz), and at different temperatures (150–340 K) is carried out. The capacitance spectra behavior in semiconductors
can be appropriately described by using abrupt cut-off models, since they assume that the electronic gap states that can follow
the ac modulation have response times varying rapidly with a certain abscissa, which is dependent on both temperature and
frequency. Two models based on the abrupt cut-off concept, formerly developed to describe inorganic semiconductor devices,
have been used to analyze the capacitance spectra of devices based on doped polyaniline (PANI), which is a well-known polymeric
semiconductor with innumerous potential technological applications. The application of these models allowed the determination
of significant parameters, such as Debye length (≈20 nm), position of bulk Fermi level (≈320 meV) and associated density of
states (≈2×1018 eV−1 cm−3), width of the space charge region (≈70 nm), built-in potential (≈780 meV), and the gap states’ distribution. 相似文献
13.
Karen B. Paul 《Central European Journal of Physics》2005,3(1):115-126
A monocrystal ofFe
3
O
4 is characterized by resistance, magnetoresistance and magnetic measurements in a temperature range from 4.2 K to 350 K and
magnetic field-cycling from −9 T to 9 T. The resistance measurements revealed a metal-insulator Verwey transition (VT) atT
v
=123.76 K with activation energy E=92.5 meV at T >T
v
and temperature-substitute for the activation energy below the VT,T
0=E/k
B
≈3800 K within 70 K–110K. The magnetotransport results independently verified the VT at 123.70 K, with discontinuous change
in the magnetic moment ΔM≈0.21 ΔM≈0.21μ
B
and resistance hysteresis, dependent on the magnetic field in a narrow temperature range of 0.4° around theT
v
. The magnetic characterization established self consistentlyT
v
as ≈123.67 K, the jump in the magnetization at the VT≈0.25μ
B
and confirmed, that the magnetocrystalline anisotropy is the main microscopic mechanism responsible for the magnetization
of the monocrystal (88%) with additional natural and imposed defects contributing as 12%. 相似文献
14.
A. V. Glushkov V. B. Kosarev I. T. Makarov I. E. Sleptsov S. A. Filippov 《JETP Letters》1998,67(6):383-388
Preliminary results are reported from an investigation of the temporal structure of the muon disk in extensive air showers
(EASs) with primary energy E
0≥6×1016eV at distances 100–1500 m from the axis. The investigation is performed at the Yakutsk array using the large muon detector,
which commenced operation in November 1995, with a planned area 184 m2 and a detection threshold E
μ≈0.5· sec θ GeV. For E
0>1018eV it is found that the thickness of the muon disk tends to decrease. This requires substantial changes in our notions of
the development of EASs.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 6, 361–366 (25 March 1998) 相似文献
15.
Anomalies of the low-temperature specific heat of the cuprates La2CuO4 and La2−x
MxCuO4 (M = Sr, Ba)
K. A. Kvavadze M. M. Nadareishvili G. G. Basiliya D. D. Igitkhanishvili L. A. Tarkhnishvili Sh. V. Dvali 《Physics of the Solid State》1997,39(6):897-900
The low-temperature specific heat of the cuprates La2CuO4, La2−x
MxCuO4 (M = Sr, Ba) in the temperature interval 2–45 K has been investigated by the technique of pulsed differential calorimetry.
It is found that the coefficient of the residual linear term in the specific heat remains constant in the entire experimental
temperature interval. It is shown that La atoms play a special role in the formation of the anomaly, associated with the specific
nature of the interaction of these atoms with their environment, in the acoustic region of the phonon spectrum of these objects
near 6 meV.
Fiz. Tverd. Tela (St. Petersburg) 39, 1000–1004 (June 1997) 相似文献
16.
A. A. Voronkov B. P. Gorshunov V. S. Nozdrin E. S. Zhukova T. Matsuoka K. Tanaka S. Miyasaka S. Tajima M. Dressel 《JETP Letters》2012,94(9):708-713
The spectra of the conductivity and dielectric constant of La1.87Sr0.13CuO4 cuprate have been directly measured in the frequency range of 0.3 to 1.2 THz (10–40 cm−1) and the temperature range of 5 to 300 K in the E | c polarization (the electric field vector of radiation is perpendicular to the copper-oxygen planes). Excitation has been observed
in the superconducting phase, and its nature has been attributed to the transverse optical excitation of the condensate of
Cooper pairs, which appears because Josephson junctions between CuO planes are modulated due to in-plane magnetic and charge
stripes. Additional quasiparticle absorption of unknown origin has been detected at frequencies below ≈15 cm−1 at liquid helium temperatures. 相似文献
17.
L. V. Nomerovannaya A. A. Makhnëv A. Yu. Rumyantsev 《Physics of the Solid State》1999,41(8):1322-1326
An ellipsometric method is used to study the dispersion of the real ɛ
1(ω) and imaginary ɛ
2(ω) parts of the complex dielectric permittivity of single-crystal La1−x
SrxMnO3 (x=0.1, 0.2, and 0.3) for energies from 100 meV to 5 eV at room temperature. It is found that, when lanthanum is replaced by
strontium, the optical spectrum changes fundamentally. A shift in the main features of the spectrum of initial LaMnO3 at 1.9 and 4.7 eV to lower energies takes place, as well as a partial redistribution of the optical-conductivity spectral
weight in the band gap region E<1.7 eV. For compositions with x=0.2 and 0.3, a fine structure of the interband absorption is observed against a background of non-Drude optical conductivity
at low energies.
Fiz. Tverd. Tela (St. Petersburg) 41, 1445–1449 (August 1999) 相似文献
18.
Low-temperature (120–180 K) relaxational effects are observed in oxygen-deficient RBa2Cu3O6+x
(R=Y, Tm, Lu) single crystals. Isothermal holding of the crystals after rapid cooling increases their resistance. The characteristic
times and the activation energy of the relaxation process, E
a
≈0.46 eV, are determined. The possible relation between the observed effects and the appearance of “electronic phase separation”
is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 10, 788–791 (25 May 1996) 相似文献
19.
Ya. G. Ponomarev S. A. Kuzmichev M. G. Mikheev M. V. Sudakova S. N. Tchesnokov T. E. Shanygina O. S. Volkova A. N. Vasiliev Th. Wolf 《Journal of Experimental and Theoretical Physics》2011,113(3):459-467
Current-voltage characteristics (CVCs) of Andreev superconductor-constriction-superconductor (ScS) contacts in polycrystalline
samples of FeSe with the critical temperature T
C = (12 ± 1) K have been measured using the break-junction technique. In Sharvin-type nanocontacts, two sets of subharmonic
gap structures were detected due to multiple Andreev reflections, indicating the existence of two nodeless superconducting
gaps Δ
L
= (2.75 ± 0.3) meV and Δ
S
= (0.8 ± 0.2) meV. Well-shaped CVCs for stacks of Andreev contacts with up to five contacts were observed due to the layered
structure of FeSe (the intrinsic multiple Andreev reflections effect). An additional fine structure in the CVCs of Andreev
ScS nanocontacts is attributed to the existence of a Leggett mode. A linear relation between the superconducting gap Δ
L
and the magnetic resonance energy E
magres ≈ 2Δ
L
is found to be valid for layered iron pnictides. 相似文献
20.
S. B. Vakhrushev A. A. Naberezhnov N. M. Okuneva B. N. Savenko 《Physics of the Solid State》1998,40(10):1728-1733
The temperature dependence of the intensity of the Bragg and the transverse component of quasi-elastic neutron scattering
from the single-crystal model relaxor PbMg1/3Nb2/3O3 (PMN) has been studied for various applied electric fields. It is shown that application of a field E>E
th ≈1.6 kV/cm increases the elastic scattering intensity and reduces the intensity of the transverse diffuse-scattering component
and that, below 230 K and for E>6 kV/cm, the elastic-scattering intensity saturates while the temperature-dependent part of the transverse diffuse-scattering
component becomes practically suppressed. The measured temperature and field dependences of the intensity of type (h00) and (hh0) Bragg reflections provide supportive evidence both for the presence of considerable lead-ion displacements relative to
the ideal perovskite sites and for the existence in strong electric fields of an induced transition to the ferroelectric phase
below 250 K.
Fiz. Tverd. Tela (St. Petersburg) 40, 1905–1910 (October 1998) 相似文献