| 1. |
- Fistul, M. V., et al.
(författare)
-
Radiation-induced quantum interference in low-dimensional n-p junctions
- 2010
-
Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 82:12
-
Tidskriftsartikel (refereegranskat)abstract
- We predict and analyze radiation-induced quantum interference effect in low-dimensional n-p junctions. This phenomenon manifests itself by large oscillations of the photocurrent as a function of the gate voltage or the frequency of the radiation. The oscillations result from the quantum interference between two electron paths accompanied by resonant absorption of photons. They resemble Ramsey quantum beating and Stueckelberg oscillations well known in atomic physics. The effect can be observed in one- and two-dimensional n-p junctions based on nanowires, carbon nanotubes, monolayer, or bilayer graphene nanoribbons.
|
|
| 2. |
- Naidyuk, Yu. G., et al.
(författare)
-
Stimulated emission and absorption of photons in magnetic point contacts
- 2012
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14
-
Tidskriftsartikel (refereegranskat)abstract
- Point contacts between high anisotropy ferromagnetic SmCo5 and normal metal Cu are used to achieve a strong spin-population inversion in the contact core. Subjected to microwave irradiation in resonance with the Zeeman splitting in Cu, the inverted spin population relaxes through stimulated spin-flip photon emission, detected as peaks in the point-contact resistance. Resonant spin-flip photon absorption is detected as resistance minima, corresponding to sourcing the photon field energy into the electrical circuit. These results demonstrate fundamental mechanisms that are potentially useful in designing metallic spin-based lasers.
|
|
| 3. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
-
Current-induced magnetic superstructures in exchange-spring devices
- 2012
-
Ingår i: Physical Review B. - 1098-0121. ; 86:1
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the potential to use a magnetothermoelectric instability that may be induced in a mesoscopic magnetic multilayer (F/f/F) to create and control magnetic superstructures. In the studied multilayer two strongly ferromagnetic layers (F) are coupled through a weakly ferromagnetic spacer (f) by an “exchange spring” with a temperature-dependent “spring constant” that can be varied by Joule heating caused by an electrical dc current. We show that in the current-in-plane configuration a distribution of the magnetization, which is homogeneous in the direction of the current flow, is unstable in the presence of an external magnetic field if the length L of the sample in this direction exceeds some critical value Lc∼10 μm. This spatial instability results in the spontaneous formation of a moving domain of magnetization directions, the length of which can be controlled by the bias voltage in the limit L≫Lc. Furthermore, we show that in such a situation the current-voltage characteristic has a plateau with hysteresis loops at its ends and demonstrate that if biased in the plateau region the studied device functions as an exponentially precise current stabilizer.
|
|
| 4. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
-
Dynamics of current-induced magnetic superstructures in exchange-spring devices
- 2012
-
Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 38:7, s. 626-632
-
Tidskriftsartikel (refereegranskat)abstract
- Thermoelectric manipulation of the magnetization of a magnetic layered stack in which a low-Curie temperature magnet is sandwiched between two strong magnets (exchange spring device) is considered. Controllable Joule heating produced by a current flowing in the plane of the magnetic stack (CIP configuration) induces a spatial magnetic and thermal structure along the current flow - a magnetothermal-electric domain (soliton). We show that such a structure can experience oscillatory in time dynamics if the magnetic stack is incorporated into an electric circuit in series with an inductor. The excitation of these magnetothermionic oscillations follow the scenario either of “soft” or “hard” instability: in the latter case oscillations arise if the initial perturbation is large enough. The frequency of the temporal oscillations is of the order of 105–107s–1 for current densities j∼106–107A/cm2.
|
|
| 5. |
- Kadigrobov, Anatoli M., 1937
(författare)
-
Electric instability in superconductor-normal conductor ring
- 2004
-
Ingår i: EUROPHYSICS LETTERS. - 0295-5075. ; 67:2, s. 273-279
-
Tidskriftsartikel (refereegranskat)abstract
- Non-linear electrodynamics of a ring-shaped Andreev interferometer (superconductor/normal conductor/ superconductor hybrid structure) coupled to a circuit of the dissipative current is investigated. The current-voltage characteristics (CVC) is demonstrated to be a series of loops with several branches intersecting at the CVC origin. The sensitivity of the transport current J(d) (or the applied voltage V) to a change of the external magnetic flux can be the same as the sensitivity of conventional SQUIDs. Spontaneous arising of coupled non-linear oscillations of the transport current, the Josephson current and the magnetic flux in Andreev interferometers are also predicted and investigated. The frequency of these oscillations can be varied in a wide range, while the maximal frequency can reach omega(max) similar to 10(12) s(-1).
|
|
| 6. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
-
Giant lasing effect in magnetic nanoconductors
- 2004
-
Ingår i: Europhysics Letters. - : IOP Publishing. - 1286-4854 .- 0295-5075. ; 67:6, s. 948-954
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a new principle for a compact solid-state laser in the 1–100 THz regime. This is a frequency range where attempts to fabricate small-size lasers up to now have met severe technical problems. The proposed laser is based on a new mechanism for creating spin-flip processes in ferromagnetic conductors. The mechanism is due to the interaction of light with conduction electrons; the interaction strength, being proportional to the large exchange energy, exceeds the Zeeman interaction by orders of magnitude. On the basis of this interaction, a giant lasing effect is predicted in a system where a population inversion has been created by tunneling injection of spin-polarized electrons from one ferromagnetic conductor to another—the magnetization of the two ferromagnets having different orientations. Using experimental data for ferromagnetic manganese perovskites with nearly 100% spin polarization, we show the laser frequency to be in the range 1–100 THz. The optical gain is estimated to be of order 107 cm−1, which exceeds the gain of conventional semiconductor lasers by 3 or 4 orders of magnitude. A relevant experimental study is proposed and discussed.
|
|
| 7. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
-
Giant lasing effect in magnetic point contacts and its detection by DC electrical measurements
- 2011
-
Ingår i: Proc. of SPIE. - 0277-786X. - 9780819484703 ; 7933
-
Konferensbidrag (refereegranskat)abstract
- We propose a new principle for a compact solid-state laser in 1-100 THz regime based on a new mechanism for creating spin-flip processes in ferromagnetic conductors. On the base of this mechanism, a giant lasing effect is predicted. The optical gain is estimated to exceed the optical gain of conventional semiconductor lasers by 4 or 5 orders of magnitude. We propose to use a point contact between ferromagnetic metals in order to create an inverted spin-population of hot electrons in the contact region. While point contact spectroscopy is an established technology the use of magnetic point contacts as a photon source is a new and potentially very useful application. We show that the generated photons conveniently can be detected by measuring the current through the illuminated point contact.
|
|
| 8. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
-
Giant oscillations of the density of states and the conductance in a ferromagnetic conductor coupled to two superconductors
- 2005
-
Ingår i: Progress in Ferromagnetism Research. - 1594543356 ; , s. 147-169
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Giant oscillations of the density of electronic states and the differential conductance of a superconductor-ferromagnet-superconductor structure are predicted for the case when the exchange energy, $I_0$, due to the interaction between the electron spin and the spontaneous moment of the ferromagnet is smaller than the superconductor energy gap, $\Delta$. The effect is due to the extremely large degeneration of the energy level $\epsilon = I_0$ when the superconductor phase difference $\phi$ is close to odd multiple of $\pi$ ($\epsilon$ is the electron energy measured from the Fermi-energy). This quantum interference effect persists even in long ferromagnetic bridges whose length much exceeds the ''magnetic length'' ($\hbar v_{F}/I_{0}$ in the ballistic regime and $\sqrt{\hbar D/I_0}$ in the diffusive regime; $D$ is the electron diffusion constant). The predicted effect allows a direct spectroscopy of Andreev levels in the ferromagnet as well as a direct measurement of the exchange energy,$I_0$
|
|
| 9. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
-
Hot electrons in magnetic point contacts as a photon source
- 2011
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- We propose to use a point contact between a ferromagnetic and a normal metal in the presence of a magnetic field for creating a large inverted spin population of hot electrons in the contact core. The key point of the proposal is that when these hot electrons relax by flipping their spin, microwave photons are emitted, with a frequency tunable by the applied magnetic field. While point contacts are an established technology, their use as a photon source is a new and potentially very useful application. We show that this photon emission process can be detected by means of transport spectroscopy and demonstrate stimulated emission of radiation in the 10–100 GHz range for a model point contact system using a minority-spin ferromagnetic injector. These results can potentially lead to new types of lasers based on spin injection in metals.
|
|
| 10. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
-
Joule heating and current-induced instabilities in magnetic nanocontacts
- 2006
-
Ingår i: Physical Review B. - 1098-0121 .- 1550-235X. ; 74:19
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the electrical current through a magnetic point contact in the limit of a strong inelastic scattering of electrons. In this limit local Joule heating of the contact region plays a decisive role in determining the transport properties of the point contact. We show that if an applied constant bias voltage exceeds a critical value, the stationary state of the system is unstable, and that periodic, nonharmonic oscillations in time of both the electrical current through the contact and the local temperature in the contact region develop spontaneously. Our estimations show that the necessary experimental conditions for observing such oscillations with characteristic frequencies in the range 10(8)-10(9) Hz can easily be met. We also show a possibility to manipulate upon the magnetization direction of a magnetic grain coupled through a point contact to a bulk ferromagnet by exciting the above-mentioned thermal-electric oscillations.
|
|
