55 research outputs found
THz transmission spectroscopy of charge carriers in semiconductor heterostructures under surface electric fields
No full textQuanteneinschränkung in Halbleiterheterostrukturen ist ein Phänomen, das zur Quantisierung der Leitungs- und Valenzbänder führt. Abhängig von der Art der Einschränkung in den Heterostrukturen, werden quasi-2D/1D Subbänder oder 0D-Sublevel erzeugt. Die Abstände zwischen diesen quantisierten Bändern oder Levels sind wichtige Parameter, die in den letzten Jahren für Geräteanwendungen perfektioniert wurden. Die meisten dieser Geräte bilden nieder-dimensionale Ladungsträger, die potentiell die Möglichkeit für optische Übergänge zwischen den Subbändern oder Sublevels innerhalb des Leitungsbandes und des Valenzbandes erlauben. Diese Übergänge befinden sich typischerweise im Infrarot-Bereich des elektromagnetischen Spektrums und können für die gewünschte Anwendung maßgeschneidert entwickelt werden. Somit ist ein genaues Verständnis und die Kontrolle solcher Intersubband- und Intersublevelübergänge nicht nur ein wichtiger Aspekt der Grundlagenforschung, sondern auch notwendig für Anwendungen.Quantum confinement in semiconductor nanostructures is a phenomenon which leads to the quantization of conduction and valence band. Depending on the type of confinement in the heterostructures, quasi-2D/1D subbands or 0D-sublevels are formed. The spacing between these quantized bands or levels are very important parameters, which have been perfected over the years into device applications. Most of these devices form low-dimensional charge-carriers, which potentially allow optical transitions between the subbands or sublevels within the conduction and valence bands in the nanostructures. These transitions typically lie in the infrared region of the electromagnetic spectrum and can be designed according to the application in demand. Thus a strong understanding and control of such intersubband or intersublevel transitions is not only an important aspect of fundamental research, but also a necessity for device applications
HETNET neighbour handover cell list optimization based on cognitive programmed threshold response
No full textExploring ultrafast dynamics of electrons in heavy fermions by THz time-domain spectroscopy
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Resource Allocation Strategy using optimal power control for mitigating two-tier interference in heterogeneous networks
No full textThe Missing Middle
Full text linkThough recent economic growth in India has increased productivity and living standards significantly, the need for more growth and more reform remains. Rapid growth of unskilled labor-intensive manufacturing combined with growth of productivity in agriculture is necessary to enable a more inclusive growth that raises living standards in rural areas and in non-agricultural employment of relatively unskilled labor. Indias comparative advantage in services does not preclude the need for a rapid-manufacturing growth phase of development due to the service sectors low contribution to output and its demand for educated and skilled, as opposed to unskilled, workers. The failure of manufacturing output and employment to grow more rapidly can be attributed to (1) regulations governing enterprises in the private sector and (2) regulations covering conditions of employment of labor. Reducing the barriers to entry of unskilled labor into manufacturing and relaxing some of the most restrictive labor laws would increase prospects for even faster growth than current high rates.India, economic growth, Labour Regulations
A perspective on nonlinearities in coherent magnetization dynamics
No full textThe recent thrust in ultrafast magnetization dynamics aims at extending spintronic functionalities to terahertz frequencies. Deterministic manipulation of magnetization at the corresponding ultrashort timescales requires minute control not only over the magnetization itself but also the reservoirs it is interacting with. Although the various intricate couplings between spins, phonons, and electrons-all of which are susceptible to ultrashort laser pulses-lead to many (often nonlinear) coupling routes, magnetization-dynamical nonlinearities have remained largely underexplored. In this Perspective, we highlight recent advances and foresee future developments in the rapidly evolving field of nonlinear magnetization dynamics. Given the elementary character of coherent excitations, we put particular emphasis on their nonlinearities. We briefly review theoretical aspects and assess excitation mechanisms to reach the nonlinear regime of magnetic excitations in a broad class of magnetic materials, such as ferromagnets, antiferromagnets, and ferrimagnets. We present an overview of the groundbreaking experiments that showcase the unique insights provided by magnetic nonlinearities. We conclude by discussing open challenges and opportunities that underpin the potential of nonlinear magnetization dynamics for the advancement of spintronics and cavity quantum electrodynamics with spin waves at terahertz frequencies
Quantum Confinement in High Electron Mobility Transistors in Different Types of Field Effect Transistors
No full textCritical slowing down near a magnetic quantum phase transition with fermionic breakdown
Full text linkA universal phenomenon in phase transitions is critical slowing down (CSD) - systems, after an initial perturbation, take an exceptionally long time to return to equilibrium. It is universally observed in the dynamics of bosonic excitations, like order-parameter collective modes, but it is not generally expected to occur for fermionic excitations because of the half-integer nature of the fermionic spin. Direct observation of CSD in fermionic excitations or quasiparticles would therefore be of fundamental significance. Here, we observe fermionic CSD in the heavy-fermion (HF) compound YbRhSi by terahertz time-domain spectroscopy. HFs are compound objects with a strongly enhanced effective mass, composed of itinerant and localized electronic states. We see that near the quantum phase transition in YbRhSi the build-up of spectral weight of the HFs towards the Kondo temperature K is followed by a logarithmic rise of the quasiparticle excitation rate on the heavy-Fermi-liquid side of the quantum phase transition below K. A critical two-band HF liquid theory shows that this is indicative of fermionic CSD. This CSD is a clear indication that the HF quasiparticles experience a breakdown near the quantum phase transition, and the critical exponent of this breakdown introduces a classification of fermionic quantum phase transitions analogous to thermodynamic phase transitions - solution to a long-standing problem.6 pages, 4 figures. Nature Phys. (2023
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