What is an insulator in chemistry and how does it relate to superconductivity and quantum computing?

Factual Questions
1

Hi,

What is an insulator in chemistry and how does it relate to superconductivity and quantum computing?

I’ve been looking at articles on Han Purple and its properties. I haven’t found any satisfactory articles explaining its description as a

  1. 3-D insulator (what does that mean??) and the
  2. implications for superconductivity and quantum computing/science.

I look forward to your feedback.

2

I’m sure that someone more knowledgeable than me will chip in with more information but:

  1. An insulator is something that keeps things separated (in general terms). In daily life, we mostly use the word to refer to thermal insulators (which keep temperature differences from merging again). In physics and chemistry, I believe that the term mostly refers to electrical insulation (e.g., the rubber sheath on a power cable).

  2. I’ve only skimmed some articles, but the ones I’ve seen reference the 2D to 3D switch as being in superconductive states, not while operating as an insulator. But basically, if it’s working in 3D then it’s working like you would expect it to. If it’s working in 2D, then it’s not. From the description, I would suggest that what would happen is if you placed some electricity against it, if it’s in 3D mode, then the electricity will flow through the material in all directions. In 2D mode, it will move on a plane. Think of it like if you had a set of flat metal disks sandwiched together about a 3mm apart with just a small column connecting them in the middle. You shoot a stream of water at the face of the disks and nothing will go through. You turn them edge-wise towards the stream and it will pass right on through. This material would be like that with electricity (if I am understanding correctly).

  3. I assume that the ability to have a superconductive material that can change its properties based on orientation could be useful to some applications. Most computers don’t operate at superconductive temperatures, so a technology that requires you to be working at near 0 kelvin temperatures isn’t terribuly useful. Quantum computers, as they exist today, do operate at near 0 kelvin, so anything in that range that has interesting properties is liable to be useful. Your average silicon-based personal computer, for example, is based on a physical property of silicon that allow you make a transistor. It can become a resistor or a conductor at one end, depending on how much of a charge you apply to the other end. That allows you to turn the thing into a switch, and by hooking switches into switches, that toggle other switches, you can build up a complex device. I could see using Han Purple in a similar way at superconductive temperatures. Whether that would be directly useful for quantum computers, I don’t know, but maybe it would help to make some machinery around the quantum registers that behave in a more traditional way, that helps with the rest of the machine.

3

Thank you Sage Rat. That does clarify things a bit. I think the focus on Han Purple has been in the area of high-temperature conductivity. Does that mean room temperature and higher and what practical implications will it have? I haven’t found any mention of practical application of conductivity at higher temperatures.

4

There is no such thing as “an insulator in chemistry”.

Insulators can be used for chemistry and can be built by chemists, but their usefulness is always a physical property. You can have your electrical insulators (such as the plastic covering electrical cables) or your thermal insulators (which may even be a void, as is the case in thermoses). In the case of a molecular switch, it works as any other switch in that when it’s “off” it acts as an electrical insulator (it does not transmit electricity) and when it’s “on” it acts as an electrical conductor. For the switches on the wall, normally the “insulator” behavior is a matter of two pieces of metal being separated by air (the insulator is air), the “conductor” behavior takes place once the two pieces of metal are in contact; a “short circuit” is what happens when two pieces of metal that we didn’t want to establish contact, do. In the case of a molecular switch, the “off” state and the “on” state correspond again to different geometries, where one position is conductive and the other one is not.

For example, the family of possible molecular switches I used to study* had a bisphenyl group, two aromatic rings next to each other. The two rings could be oriented flat enough for electrons to jump between them (conductive) or exactly perpendicular, a position in which the two rings did not interact (insulator). Other families will have other pairs of geometries, other conductive mechanisms.

  • One of my conclussions was “hmmmm… nope, this particular bunch will not really work, but studying them has already given us several interesting techniques we can use for other stuff, so we’re cool.”
5

Thanks Nava for that very practical explanation.