Does Catholicism teach a physical 'New Earth' or is it only a state of mind?

This section of the Catholic Catechism addresses this issue.

VI. Hope of the New Heaven and the New Earth 1042 At the end of time, the Kingdom of God will come in its fullness. After the universal judgment, the righteous will reign for ever with Christ, glorified in body and soul. the universe itself will be renewed:

The Church . . . will receive her perfection only in the glory of heaven, when will come the time of the renewal of all things. At that time, together with the human race, the universe itself, which is so closely related to man and which attains its destiny through him, will be perfectly re-established in Christ. [LG 48; Cf. Acts 3:21; Eph 1:10; Col 1:20; 2 Pet 3:10-13]

1043 Sacred Scripture calls this mysterious renewal, which will transform humanity and the world, “new heavens and a new earth.” [2 Pet 3:13; Cf. Rev 21:1] It will be the definitive realization of God's plan to bring under a single head “all things in [Christ], things in heaven and things on earth.” [Eph 1:10]

1044 In this new universe, the heavenly Jerusalem, God will have his dwelling among men. [Cf. Rev 21:5] “He will wipe away every tear from their eyes, and death shall be no more, neither shall there be mourning nor crying nor pain any more, for the former things have passed away.” [Rev 21:4]

1045 For man, this consummation will be the final realization of the unity of the human race, which God willed from creation and of which the pilgrim Church has been “in the nature of sacrament.” [Cf. LG 1] Those who are united with Christ will form the community of the redeemed, “the holy city” of God, “the Bride, the wife of the Lamb.” [Rev 21:2, 9] She will not be wounded any longer by sin, stains, self-love, that destroy or wound the earthly community. [Cf. Rev 21:27] The beatific vision, in which God opens himself in an inexhaustible way to the elect, will be the ever-flowing well-spring of happiness, peace, and mutual communion.

1046 For the cosmos, Revelation affirms the profound common destiny of the material world and man:

For the creation waits with eager longing for the revealing of the sons of God . . . in hope because the creation itself will be set free from its bondage to decay.... We know that the whole creation has been groaning in travail together until now; and not only the creation, but we ourselves, who have the first fruits of the Spirit, groan inwardly as we wait for adoption as sons, the redemption of our bodies. [Rom 8:19-23]

1047 The visible universe, then, is itself destined to be transformed, “so that the world itself, restored to its original state, facing no further obstacles, should be at the service of the just,” sharing their glorification in the risen Jesus Christ. [St. Irenaeus, Adv. haeres. 5, 32, 1 PG 7/2, 210]

1048 “We know neither the moment of the consummation of the earth and of man, nor the way in which the universe will be transformed. the form of this world, distorted by sin, is passing away, and we are taught that God is preparing a new dwelling and a new earth in which righteousness dwells, in which happiness will fill and surpass all the desires of peace arising in the hearts of men.” [GS 39 # 1]

1049 “Far from diminishing our concern to develop this earth, the expectancy of a new earth should spur us on, for it is here that the body of a new human family grows, foreshadowing in some way the age which is to come. That is why, although we must be careful to distinguish earthly progress clearly from the increase of the kingdom of Christ, such progress is of vital concern to the kingdom of God, insofar as it can contribute to the better ordering of human society.” [GS 39 # 2]

1050 “When we have spread on earth the fruits of our nature and our enterprise . . . according to the command of the Lord and in his Spirit, we will find them once again, cleansed this time from the stain of sin, illuminated and transfigured, when Christ presents to his Father an eternal and universal kingdom.” [GS 39 # 3] God will then be “all in all” in eternal life: [1 Cor 5:28]

True and subsistent life consists in this: the Father, through the Son and in the Holy Spirit, pouring out his heavenly gifts on all things without exception. Thanks to his mercy, we too, men that we are, have received the inalienable promise of eternal life. [St. Cyril of Jerusalem, Catech. illum. 18, 29: PG 33, 1049]