I close my eyes and remember vividly: The year is 1975. I am 21. I am standing in the shabby office shared by Eugene Maksimov, Lev Bulaevskii, and Daniel. I am looking for an MSc advisor. Eugene tells me that he is working on high Tc superconductivity, Lev on 1D and 2D metals, and Daniel on orbital ordering and Hubbard model. The last part is lost on me, and definitely does not have the romantics of high-temperature superconductivity. I choose Eugene.

For the next two years I woul be reading frantically AGD[1], Schrieffer[2], Ziman[3]. None of them as much as mention the Hubbard model. I attend two weekly seminars[4]. Yuri Kopaev speaks about excitonic insulators and toroidal moments. Lev speaks about organic metals. Geli Zharkov about 2D “sandwich” superconductivity. It’s all definitely more exciting than orbital ordering and Hubbard model. Ginzburg politely suggests that Khomskii applies his talents to something more interesting, like superconductivity. It’s like Wright brother chastised by Edison (not that it ever happened) for spending their time on dubious flying machines with no foreseeable future rather than improving bicycles.

Science aside, another flashback. It is probably early 80-s. Danya and I are at a conference in Carpathian Mountains and plan to take a few days off for downhill skiing. I am seventeen years younger and (I think) pretty tough, and Danya looks like a proverbial absent-minded professor, short-ish, with thick glasses, and overall nerdish look. So, I mention, a big condescendingly, how we had done a week-long cross-country skiing backpacking, pitching tents on the snow. Danya is very responsive, “yes, sure, I did it when I was younger. Once, it was -20 C (<0 F), and we did not have sleeping bags then, just blankets. It was pretty tough!”

And, now a flashforward. I am on sabbatical in Cologne. The year is 2006. Day after day, we are sitting with Danya, like two linguists composing a dictionary between two exotic languages. “This is how you get this interaction in the Hubbard model” – quoth Daniel. Me: “I can get the same interaction in DFT, here, here and here. Your Hund’s rule coupling now appears as my Stoner parameter on oxygen”. And we then compare the numbers, and see how much the formulaic is the same, even though there are quantitative differences, and to our own astonishment, we get a lot of mileage for ourselves, learning to do these mental translations. “Being bilingual makes you smarter and can have a profound effect on your brain”, claims New York Times[5]. Thank you, Daniel, for teaching me your language!

Nearly 50 years I have been blessed with your company. Sometimes I used it more, sometimes less. But I would not have been what I am now without having known you and partaking of your wisdom.

[1] A. Abrikosov, L. P. Gorkov and I. E. Dzyaloshinski. Methods of Quantum Field Theory in Statistical Physics.
[2] J. R. Schrieffer. Theory of Superconductivity
[3] J. M. Ziman. Principles of the Theory of Solids
[4] I. I. Mazin. Vitaly Ginzburg and high temperature superconductivity: Personal reminiscences. Physica C 468, 105-110 (2008)
[5] https://www.nytimes.com/2012/03/18/opinion/sunday/the-benefits-of-bilingualism.html

A great scientist, whose name is the name of one of the theoretical models, has passed away. He has always been at the forefront of science and, one might say, defined this cutting edge himself. He was distinguished by his ability to generate scientific ideas and susceptibility to alternative points of view.

Thanks to his scientific creativity, he opened the way to world science for many researchers. He was actively published: only in collaboration with the staff of the Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences, he acted as a co-author of fifty scientific papers.

His memory will be grateful and bright. I would like to believe that other researchers, like us, will be lucky enough to meet on their way such a colleague and well-wisher as Daniel Khomskii.

We are loosing a friend and a very inspiring scientist. Last century, we met in the Alps attending a European meeting organized by Coey on oxides for spintronics ; for the 1st time, I was stopped during my talk: obviously a question from Daniil. Since then our discussions were productive and we had a chance to co-author 10 publications. We will miss his legendary scientific curiosity and contagious enthusiasm, not to mention his exceptional understanding of transition metal oxides physics.
My thoughts go to his family.