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Photon-Assisted Heat Generation by Electric Current in a Quantum Dot Attached to Ferromagnetic Leads
摘要： Heat generated by electric current in a quantum dot device contacting a phonon bath is studied using the non-equilibrium Green function technique. Spin-polarized current is generated owing to the Zeeman splitting of the dot level. The current’s strength and the spin polarization are further manipulated by changing the frequency of an applied photon field and the ferromagnetism on the leads. We find that the associated heat by this spin-polarized current emerges even if the bias voltage is smaller than the phonon energy quanta and obvious negative differential of the heat generation develops when the photon frequency exceeds that of the phonon. It is also found that both the strength and the resonant peaks’ position of the heat generation can be tuned by changing the value and the arrangement configurations of the magnetic moments of the two leads, and then provides an effective method to generate large spin-polarized current with weak heat. Such a result may be useful in designing low energy consumption spintronic devices.
关键词： quantum dot,heat generation,ferromagnetic leads,photon-assisted tunneling,spin-polarized current
更新于2025-09-23 15:19:57
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DC measurement of dressed states in a coupled 100?GHz resonator system using a single quasiparticle transistor as a sensitive microwave detector
摘要： We report on the on-chip detection of microwaves in the frequency range around 100 GHz. For the purpose of detection, we employ a discrete transport channel triggered in a superconducting single-electron transistor by photon-assisted tunneling of quasiparticles. The technique is applied to observe the spectrum of the dressed states of a model circuit quantum electrodynamics system consisting of a superconducting coplanar resonator coupled to a Josephson oscillator. The dressed states appear as typical resonance anticrossing exhibiting, in our case, an expectedly wide frequency splitting corresponding to the Jaynes–Cummings coupling strength, g=p (cid:2) 10 GHz. Due to the high decay rate, c (cid:2) 20–40 GHz, in the very transparent Josephson junctions used, the strong coupling limit, g (cid:3) c, which is required for qubit operation, is not achieved, and the photon population in the resonator is low, hni < 1. Remarkably, the continuous readout of the low population states demonstrates the high microwave sensitivity of the detector.
关键词： photon-assisted tunneling,dressed states,superconducting single-electron transistor,circuit quantum electrodynamics,microwave detection
更新于2025-09-12 10:27:22
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Direct and photon-assisted tunneling in resonant-cavity quantum-well light-emitting transistors
摘要： Tunneling in a transistor is a critical quantum process toward the next-generation, energy-efficient, high-speed data transfer for both electrical and optical communications. In this work, resonant-cavity quantum-well light-emitting transistors with tunneling collector junctions are designed and fabricated. Three distinctive tunneling mechanisms are clearly identified by the transistor optical output family curves, namely, electron direct tunneling (DT) from collector to base, electron DT from base to collector, and intra-cavity photon-assisted electron tunneling from base to collector. The device operations under both direct and photon-assisted tunneling are explained in detail by the intra-cavity quantum transition of electron-hole pair to photon dynamics. The tunnel junction and the corresponding carrier tunneling injection suggest the possibility of utilizing tunneling to achieve high-speed optoelectronics operations.
关键词： photon-assisted tunneling,optoelectronics,quantum-well,resonant-cavity,light-emitting,transistor,tunneling
更新于2025-09-04 15:30:14