Do electrons jump from one wire to another if they are of different materials?

Question

I learnt from this answer to the question - Do electrons in a wire, actually jump across two metallic wires twisted together? - that electrons jump from one wire to another wire in contact, when electric current exists in both wires along the same direction, as shown below:

What happens if the two wires carrying current in the same direction are of different materials, say aluminium and copper, as given below?:

Will electrons jump from the copper wire to the aluminium wire and vice versa?

In the first case, the two wires are of the same material (say copper) and so at a given temperature, the drift speed of electrons as well as the lattice of the materials are same. So, it seems reasonable that electrons do jump from one wire to another.

But in the second case, since the wires are of different materials both drift speed and lattice of the materials are different in each wire. So, I think there must be some different in the way electrons drift between the two wires. Is this transfer kind of "one-way"? For example, will electrons flow only from the copper wire to the aluminium but not the other way round?

Let us assume that the two wires are in contact with each other (i.e., no oxide layer preventing electrical contact between them) and they are maintained at a constant potential difference. Is the combination of wires, simply a parallel or a more complicated one due to transfer of electrons between them?

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^{Note: The above question was closed as a duplicate of tranfser of electrons between two metals and a wire. However, I didn't find it useful.}

Answer 1

Yes, they can jump between different materials. This is used all the time when engineering setups where the experimentalist wants to induce some new properties on the electrons in one of the materials. These are called heterostructures, and for example you can induce superconductivity in a semiconductor by proximity coupling them. The idea is that the electrons in the semiconductor can hop onto the superconductor and then return as holes, thereby inducing an effective (weak) superconductivity term in the semiconductor.

If you google "superconductor-semiconductor heterostructure" you will get ton of results.

Answer 2

If electrons were not able to flow between two different conductors in contact with one another, we would not be able to make any connections in an electrical circuit that feeds loads. So obviously they can flow between conductors in contact with one another (twisted,or otherwise).

The term "jump" invokes the wrong impression that electrons need to leap through the air from one conductor to another, although as explained below arcing is possible at the conductor interface.

Although electrons don't have to "jump" between the conductors, it is more difficult for electrons to cross between two physically different conductors due to microscopic irregularities at the contact surfaces with points of contact and areas of non contact. Overall, this gives rise to what is referred to as contact resistance at the interface. Contact resistance, which is greater than the resistance of the conductor themselves, give rise to resistance heating, and sometimes overheating posing an ignition and fire hazard, particularly if electrical connections are not made properly. For this reason electrical connections are usually considered to be the weak links in an electrical circuit due to the possibility of overheating.

Incidentally, overheating was a problem for copper aluminum connections to to a combination of making poor connections and the partial incompatibility of the different materials.

Hope this helps.