Designing a highly efficient graphene quantum spin heat engine

Abstract

We design a quantum spin heat engine using spin polarized ballistic modes generated in a strained graphene monolayer doped with a magnetic impurity. We observe remarkably large efficiency and large thermoelectric figure of merit both for the charge as well as spin variants of the quantum heat engine. This suggests the use of this device as a highly efficient quantum heat engine for charge as well as spin based transport. Further, a comparison is drawn between the device characteristics of a graphene spin heat engine against a quantum spin Hall heat engine. The reason being edge modes because of their origin should give much better performance. In this respect we observe our graphene based spin heat engine can almost match the performance characteristics of a quantum spin Hall heat engine. Finally, we show that a pure spin current can be transported in our device in absence of any charge current.

Enhancement of the thermoelectric properties in bilayer graphene structures induced by Fano resonances

“…For instance, the maximum power at K is 0.5387 pW /K , while at K is 1.755 pW /K . These values are more than an order of magnitude higher than the ones reported in strained single layer graphene 54 . In fact, the maximum power of single barriers is a monotonous increasing function of the temperature.…”

“…In fact, this similarity between both conductances is what makes that the Seebeck coefficient shapes the ZT characteristics. However, the ZT values are not as high as in the case of strained single layer graphene with a spin flipper 54 , because is not proportional to the Lorenz number in the entire chemical potential energy range. Actually, this quantity attains large values in the energy regions in which is large as well, resulting in values of ZT up to 1.7.…”

“…The electronic thermal conductance is similar to the electrical conductance. However, the ratio of to GT is not at all the Lorenz number, resulting in values of ZT an order of magnitude lower than in strained single layer graphene 54 . More details about can be found in the supplementary information .…”

“…With the transport coefficients we can also compute straightforwardly the maximum power 54 and the efficiency at maximum power 54 To end this section, we will give the fundamentals to determine the density of states (DOS) of single and double barriers. This calculation will give us the possibility of know if the accumulation of electron states is related to the improvement of the thermoelectric response.…”

Modulating the Spin Seebeck Effect in Co2FeAl Heusler Alloy for Sensor Applications

“…However, usually, these systems present a high heat resistance, leading to limitations in biosensor applications [4]. On the other hand, thermoelectric effects based on spin dynamics have received increasing attention in recent past, not just to the great technological potential in power-saving electronic devices [5][6][7][8][9], but also for photodetectors [10,11], diode [12], and temperature sensor [13].…”